Continuing a series begun last year, we asked D. John Doyle, MD, PhD, a member of the Anesthesiology News advisory board, to pose 7 questions to an international airway management roundtable, whose members he picked. The responses, including those of Dr Doyle, follow.

1. John Doyle, MD, PhD

Chief of General Anesthesiology

Anesthesiology Institute

Cleveland Clinic Abu Dhabi

Abu Dhabi, United Arab Emirates

Dr Doyle also serves as staff anesthesiologist at the Anesthesiology Institute, the Cleveland Clinic, in Cleveland, Ohio, where he is professor of anesthesiology at the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University.

 

Andrew Brainard, MD, MPH, FACEM, FACEP

Middlemore Hospital Emergency Medicine Consultant

Honorary Senior Lecturer

University of Auckland Medical School

Auckland, New Zealand

 

Prof Tim M. Cook, BA, MBBS, FRCA, FFICM

Consultant in Anaesthesia and Intensive Care Medicine

Royal United Hospital NHS Trust

Bath, United Kingdom

 

James DuCanto, MD

Director of Simulation Center

Aurora St. Luke’s Medical Center

Milwaukee, Wisconsin

 

Katherine S.L. Gil, MD

Associate Professor of Anesthesiology and Neurological Surgery

Northwestern University Feinberg School of Medicine

Northwestern Memorial Hospital

Chicago, Illinois

Editor-in-Chief,The Airway Gazette

 

Eric Hodgson, MD

Chief Specialist Anesthesiologist and Pain Specialist

Nelson R. Mandela School of Medicine

Thekwini-Durban, KwaZulu-Natal, South Africa

 

Vladimir Nekhendzy, MD

Clinical Associate Professor of Anesthesiology and Otolaryngology

Director, Stanford Head and Neck Anesthesia and Advanced Airway Management Program

Stanford University School of Medicine

Stanford, California

President, Society for Head and Neck Anesthesia

 

Prof Ellen O’Sullivan, FRCA, FCAI, FCPSP

Consultant of Anesthesia, Intensive Care, and Pain

St. James Hospital, Dublin, Ireland

Difficult Airway Society Professor of Anaesthesia and Airway Management

Past President, Difficult Airway Society

Immediate Past President, College of Anaesthetists of Ireland

 

Daniel Perin, MD, PhD

Instructor and Co-owner

Centro de Treinamento em Vias Aéreas (Airway Training Center)

Private Practice Anesthesiologist

Anesthesia Division University of São Paulo

São Paulo, Brazil

 

Felipe Urdaneta, MD

Secretary, Society for Airway Management

Professor of Anesthesia

University of Florida

North Florida/South Georgia Veterans Health System

Gainesville, Florida

 

Dr Cook disclosed that his department has received airway equipment for evaluation or research, and reported no relevant financial disclosures. Dr DuCanto disclosed that he is a consultant for Nasco, Salter Labs, and SSCOR, Inc. Dr Gildisclosed that she is the lead organizer/co-moderator for the American Society of Anesthesiologists’ (ASA’s) Basic and Advanced Adult Flexible Fiber-optic Intubation Workshop, held at the annual meeting, which is supplied through the ASA with multiple airway devices; Dr. Gil reported no relevant financial disclosures. All remaining participants report no relevant financial disclosures. Dr Urdaneta discloses that he is an unpaid consultant for Teleflex. All remaining participants reported no relevant financial disclosures.

1. What is your favorite method for topicalizing the airway for awake intubation? Do you use any needle-based airway blocks?

Dr Brainard: As an emergency medicine consultant, many of our patients who need awake intubation are not fully cooperative, are not physiologically stable, and have unknown anatomy. It is quite a different situation, with different equipment and indications than those normally encountered in the operating theater.

While awake intubation is occasionally a good airway strategy in the emergency department (ED), it should always be done in conjunction with being ready with an alternative airway strategy. The backup airway strategy must be 100% ready; this means completing a preintubation airway checklist and having a fully prepared backup plan. Our backup plan includes sedation, paralysis, and video laryngoscopy (VL), with supraglottic and surgical airways as an additional backup strategy.

As the decision to attempt an awake intubation is made, I recommend the use of a multifactorial strategy involving physical, psychological, and pharmacologic methods to most effectively assist with topicalizing the airway.

I recommend positioning patients in their most relaxed position, which is normally sitting up, jaw forward, and maintaining comforting face-to-face eye contact between the provider and the patient. I believe that, in most situations, this patient–provider eye contact aids the patient–provider therapeutic alliance, and generally creates the most cooperative environment for the awake intubation.

The psychological methods involve having the provider and team work with the patient, explaining the procedure, and getting buy-in from the patient. Even for cooperative patients, I recommend IV analgesia (fentanyl in 20-mcg aliquots and/or ketamine in 20-mg aliquots) and/or an anxiolytic (midazolam). Antisecretagogues such as atropine (0.01 mg/kg) or glycopyrrolate (0.05 mg/kg) should also be administered as soon as possible.

In addition to the IV medications, I recommend providing preoxygenation via nasal cannulas at 15 L per minute of oxygen (O2) and some upper airway topical analgesia via nebulizer mask, administering 4% lidocaine with O2 at 10 L per minute.

Some additional nasal and pharyngeal topical analgesia should then be administered by 5 sprays of co-phenylcaine into each nostril. Additionally, 5 sprays of 10% lidocaine into the oropharynx and/or the placement of viscous lidocaine on the back of the tongue with a video laryngoscopic blade can provide additional topicalization.

Finally, an appropriately sized (large) nasal pharyngeal airway, coated with viscous lidocaine, is inserted to test for appropriate cooperation and topicalization. If a channeled flexible fiber-optic scope is used, additional 4% lidocaine can be administered in a “spray as you go” (SAYGO) fashion.

Prof Cook: I use co-phenylcaine (premixed lidocaine and phenylephrine) in the nose followed by 4% lidocaine on cotton swabs, 10% lidocaine spray into the pharynx, and finally 2% via a cricothyroid puncture. The latter serves several purposes: 1) it provides excellent anesthesia of the vocal cords and of the trachea to the carina; 2) it increases general experience of cricothyroidotomy; and 3) it is very useful to get familiar with the cricothyroid membrane of the patient in front of you. Whether it is easy or difficult is highly useful information. The need for supplemental lidocaine is rare after this preparation.

Dr Doyle: I rarely use needle-based blocks, but when I do, I usually do transtracheal injection of local anesthesia. (I once even recorded such an injection from the inside of the trachea—see www.youtube.com/?watch?v=I8IF7PjDhnA). Although I was once an enthusiastic fan of needle-based blocks, I have found that less invasive techniques work very well.

My usual technique nowadays is to have the patient first gargle 2% viscous lidocaine, given with a disposable drinking cup. The lidocaine is gargled, then expectorated; most patients prefer to sit up rather than be supine for this. In addition, letting the patient hold and control the Yankauer suction tube to remove any excess anesthetic or to use after they have “had enough” can be helpful.

I usually follow this with a power sprayer to deliver 4% lidocaine to the oropharyngeal and glottic structures. Oxygen at 15 L per minute is used as the gas source. Known as “EZ-Spray,” this unit is available from Intertex Research.

I then place a Williams or Ovassapian oral airway guide, used to facilitate passage of the bronchoscope and tracheal tube. If the patient does not tolerate placement of the guide, then the topical anesthesia is inadequate, but usually this is not a problem.

Next, with the oral airway guide in place, I pass a malleable LMA MADgic Laryngo-Tracheal Mucosal Atomization Device (Teleflex) via the guide to deliver another bit of topical anesthesia to the periglottic structures. Additional anesthesia can also be administered under visual guidance via the bronchoscope.

Of course, nasal intubation requires additional topicalization of the nasal passages in conjunction with a vasoconstrictor.

Finally, judicious sedation with drugs, such as midazolam, fentanyl, or dexmedetomidine, is frequently used when awake intubation is carried out.

Safety Note: I use lidocaine exclusively; benzocaine topical anesthesia, while highly effective, is sometimes complicated by methemoglobinemia, causing the blood to appear chocolate-colored and the patient to look cyanotic. Treatment of methemoglobinemia is with methylene blue.

Dr DuCanto: I have simplified my method to the “4-syringe method” when using a flexible fiber-optic bronchoscope, with each syringe containing 3 ml of 4% lidocaine. It is quick, effective, and simple. The first syringe is administered orally to the patient with the instructions to gargle and swallow the medication. The other 3 syringes are delivered through the working channel/suction channel of the bronchoscope, with 2 applications to the vocal cords, and the final application to the trachea after scope entry. If a bronchoscope is not used, a similar method is employed by cutting the tip off a Mallinckrodt tracheal tube, allowing the medication to be injected through the pilot balloon port and straight out of the tip of the tracheal tube. Cutting the tip of the tracheal tube exposes the channel used to inflate and deflate the tracheal tube cuff; this tube is removed over an airway exchange catheter to replace it with a tracheal tube that possesses a functional cuff.

Dr Gil: My teammates and I love “3-minute triple blocks,” because this complete airway anesthesia method (see www.youtube.com/?watch?v=ij6ew7ZDeZI) is beyond doubt the most valuable for untold numbers of trainees and adult patients. Minor 22- to 23-gauge needling (no angiocatheter) causes little discomfort or recall under good sedation (or in dyspneic patients, 0 to 5-10 mg ketamine). I almost always give 0.2 to 0.4 mg glycopyrrolate 15 to 20 minutes beforehand.

For the triple block, the average dose is two-thirds the maximum allowed.

Glossopharyngeal nerve (GPN) block: Spray 1 mL of 3% lidocaine per side during inspiration, using a MADgic atomizer curved toward tonsillar pillars, even if unseen. Elicit gargling between sprays. Repeat. Lidocaine lollipops or gargles also work.

Superior laryngeal nerve (SLN) block: Inject 3 mL of 1% lidocaine at each hyoid cornu after negative aspiration. Skip hyothyroid membrane searches.

Transtracheal block (TTB): Inject 4 mL of 4% lidocaine (braced 10-mL syringe; 22- to 23-gauge needle). After very free aspiration of air through the cricothyroid membrane, repeat aspiration while asking the patient to exhale deeply. At end-exhalation, inject rapidly.

For a nasopharynx approach, spray 1 mL of 4% cocaine or oxymetazoline plus 1 mL of 4% lidocaine per side. Skip the GPN block.

Why is this the best? First, studies have found less gagging, grimacing, or laryngospasm using TTB versus SAYGO,1 as well as lidocaine gargle plus TTB versus gargle plus nebulized lidocaine.2 Even triple-block hemodynamic changes were less versus nebulized lidocaine.3,4

Second, TTB provides experience locating the cricothyroid space by getting positive air-in-the-syringe feedback. Sadly supported by a NAP4 (4th National Audit Project) study with 43% to 64% emergency cricothyroid failures,5,6 studies show only 30% accuracy by graduating residents and attendings in locating the space,7 especially in female patients—missing by up to 1.6 cm laterally, 2.5 cm superiorly, and 4 cm inferiorly.8

Third, the triple block provides complete airway anesthesia in 3 minutes.

If any of the techniques is not possible (eg, need to avoid needles in kids, coagulopathy, bad anatomy), 4% aerosolized lidocaine under a constant, very watchful eye works very well, but this takes 15 to 20 minutes. If aspiration is a significant risk, use the SAYGO option, and rapidly enter the trachea, intubate, and inflate, instead of doing an SLN or TTB block.

Dr Hodgson: Topicalization is facilitated by the administration of 0.05 mg/kg of glycopyrrolate, with patient comfort promoted by infusion of dexmedetomidine: 1- to 1.5-mcg/kg loading over 20 minutes followed by 0.4 to 0.6 mcg/kg per hour.

I use gargling with 4% lidocaine after the patient has demonstrated that he or she can gargle with water. Patients gargle until they start coughing, indicating aspiration of the lidocaine.

In those who are unable to gargle, I use the LMA MADgic Airway (Teleflex) that has a port for O2 insufflation and a mucosal atomizer device (MAD) through which 4% lidocaine can be sprayed as the device is advanced. Once the device is in place, the scope can be advanced. I place an epidural catheter through the suction channel and spray 4% lidocaine as I go.

I have given up on needle-based blocks after inducing grand mal seizures doing a GPN block via the intraoral approach.

Dr Nekhendzy: It depends on the route chosen. For an awake oral intubation, I usually spray 4% lidocaine using the DeVilbiss atomizer connected to the high-flow O2. The device has an adjustable nozzle and produces a powerful, dense, and fine spray. I do not use nebulized lidocaine, as the size of the particles produced suites better for topical anesthesia of the lower, and not the upper airway. If the patient’s cooperation is poor, I may add an intraoral 5% lidocaine ointment utilizing different variations of the “toothpaste technique” described by Drummond.9

For nasal intubation, I combine nasal/intraoral spraying with topical application of 5% lidocaine ointment to the inferior turbinate using cotton swabs. It minimizes the total amount of lidocaine absorbed through highly vascular nasal mucosal surfaces, and helps to achieve targeted, superior topical anesthesia to the most sensitive, posterior part of the turbinate.

I teach superior laryngeal and recurrent laryngeal (transtracheal) blocks to the trainees whenever feasible, although they may not be required for the majority of patients. I think knowledge of these blocks is very important for situations when you have poor patient cooperation, and for some special situations. I do not use the injection-based block of the GPN: It is uncomfortable, and blunting the gag reflex can be effectively achieved noninvasively.

Prof O’Sullivan: I mainly perform awake nasal intubation where feasible. With the patient sitting up, I examine both nostrils and choose and prepare only one side. I use co-phenylcaine (0.5% phenylephrine and 5% lidocaine) spray to the anterior mucosa and progress to the postnasal space. I also use the MADgic device. For oral topicalization I use 4% lidocaine spray to the posterior tongue and pharynx, and then have the patient gargle. I usually do this with the MADgic device. For the SAYGO technique, I place an epidural catheter through the working channel of the scope. I spray 4 mL of 4% lidocaine to the vocal cords and to the trachea when the scope is through the cords. I do not use needle blocks. I occasionally use a cannula through the cricothyroid membrane and inject 4 mL of 4% lidocaine in cases without oral pathology. I run remifentanil (Ultiva, Mylan) target-controlled infusion (TCI) at 6 ng/mL for all cases, reducing the dose in patients with stridor. It is important to have a second person in charge of the sedation to avoid oversedation, which was the cause of morbidity with fiber-optic intubation in NAP4. During the procedure, I administer nasal O2 and high-flow (30 L/min) humidified oxygen in the more difficult patients (obese, obstetrics, stridor).

Dr Perin: Starting with the oral approach, I use 2% lidocaine for topicalizing the airway. The reason for that is the absence of 4% lidocaine in the Brazilian market. I use scopolamine or atropine IV 15 minutes before starting with the local anesthetic because we also don’t have glycopyrrolate. After that, I use lidocaine jelly and gauze or the MADgic atomizer to block the GPN. The next step is to do a TTB through the cricothyroid membrane with 4 to 5 mL of 2% lidocaine in all patients, unless there is a contraindication. If I am not able to do this technique, I intubate with the SAYGO method, but it is my second choice.

The nasal approach is done by utilizing oxymetazoline 0.05% previously (5 minutes) and atomization with MADgic or jelly inside the nostrils to block the anterior ethmoidal nerve and sphenopalatine ganglion. The next step is the TTB, if possible.

I do not prepare both approaches at the same time. I perform local anesthesia regarding my first choice (oral or nasal), and, if I fail, I start again with the other option. This is because if we lose time trying to intubate orally and we are not successful, the effect of the local anesthesia ends in the nose, and very frequently we need to do it again, possibly raising local anesthetic blood levels.

Dr Urdaneta: Awake intubation requires proper patient preparation; airway reflexes must be obtunded to allow the procedure to be carried out properly. The administration of an antisialagogue before the procedure reduces the volume of secretions allowing less interference with the optics of the endoscope as well as decreasing the dilution of topical agents. The use of sedatives depends on the urgency of the situation, on the respiratory status, and reason for the awake technique. The concern for dysphoria, respiratory depression, and apnea with most sedative agents requires individualization and caution; the decision to use sedation, especially in patients with significant airway distortion and compromise, is not recommended.

For the nasal approach, I use a vasoconstrictor like oxymetazoline and, in some cases, depending on availability, liquid 4% cocaine. Cocaine has the advantage of having a dual role as a vasoconstrictor plus an anesthetic, but since it is a controlled substance, it is usually hard to find. The advantage of the nasal approach over the oral route is that there is a more direct path to the glottic opening, and one avoids the issues of glossopharyngeal innervation and the gag reflex. However, this approach also is prone to bleeding, which is very important to keep in mind when deciding the route. It also still requires anesthetizing the larynx and trachea.

For the oral route, one has to block the posterior tongue, posterior pharynx, periglottic area, and the larynx and trachea. Anesthesia can be delivered by several methods: spreading local anesthetics via topicalization, spraying, and direct needle nerve blocks. All of these techniques have benefits and drawbacks; since comfort to the patient and simplicity to providers are of paramount importance, I abandoned direct nerve blocks a long time ago. Needle blocks are excellent choices, but, as with other needle techniques, they are not exempt from risks, and not all patients are happy when you approach them with a needle to inject them close to the face and inside their mouth.

My current preferred approach depends on the degree of cooperation of the patient and the time I have to accomplish the procedure. If pressed for time, the SAYGO technique is adequate; I use 5 to 10 cc 4% liquid lidocaine using a 3-way stopcock, the working channel of the scope, and an O2 source. As I advance the scope, I instruct an assistant to inject 1 cc of anesthetic and wait for it to take effect until I advance further. If the intubation is elective and I have time, I topicalize the oropharynx with 10 cc of 2% viscous lidocaine with gauze at the tip of a tongue depressor. In order to avoid the bitter taste, I mix the solution with an artificial sweetener. Once enough gag reflex has been “eliminated,” I proceed to use aerosolized 4% liquid lidocaine and 5 to 10 cc of the solution. This is enough to block the mucosal distribution of the SLN. For the recurrent laryngeal block, I inject 2 cc of 4% lidocaine via the working channel of the scope using an epidural catheter. The total dose of lidocaine is about 500 mg, which for an adult person is within the toxic dose range. In reality, most of the lidocaine is absorbed via the gastrointestinal (GI) tract, and therefore the dose used does not reach toxic blood levels.

2. What is your favorite method for ensuring that extubation is uneventful in cases where gentle extubation is crucial?

 

Dr Brainard: Extubation is rarely indicated in our emergency room. When we do extubate patients they are either extremely low risk or are being extubated as part of their palliative care plan. In these rare occasions, I prepare the patient’s family for the expected coughing, snoring, vomiting, and/or apnea, suction the patient, deflate the cuff, and withdraw the tube.

Prof Cook: My anesthetic practice is essentially a total IV anesthesia (TIVA)-based one. This dramatically reduces airway reactivity during all phases of anesthesia. For most big cases, I supplement propofol TIVA with low-dose remifentanil infusion (eg, 2 ng/mL). This combination provides excellent extubation and emergence characteristics. Where specific difficulty is anticipated, I either maintain low-dose remifentanil infusion throughout the extubation or, with the patient deep, I insert an LMA ProSeal (Teleflex) posterior to the tracheal tube, and then remove the tracheal tube before allowing the patient to emerge with the LMA ProSeal in situ (a version of the Bailey procedure10). Both techniques are described in the UK Difficult Airway Society extubation guidelines.11

Dr Doyle: There are 3 things that I sometimes do. The most common thing is to use an adjunctive remifentanil infusion for the case (eg, 0.1 mcg/kg/min) and then to turn the remifentanil off at just the right time, waiting for the patient to quietly emerge from anesthesia. Sometimes, however, I keep the remifentanil infusion going at a very reduced rate (eg, 0.01 mcg/kg/min) instead of turning it off entirely.

A second thing I sometimes do while the patient is still deep is to disconnect the patient from the ventilator, evacuate the endotracheal tube (ETT) cuff of all air, inject 100 mg of lidocaine down the ETT lumen, ventilate with the cuff down to help redistribute the lidocaine under the uninflated cuff, and then reinflate the cuff. The idea is to allow the trachea to better tolerate the ETT with subsequent emergence.

Finally, I sometimes extubate while the patient is deep and then wake him or her after placing a supraglottic airway (SGA) device such as an i-gel (Intersurgical).

Dr DuCanto: Proper medication is essential to ensure that the patient is calm, whether in the operating room (OR) or intensive care unit (ICU). Proper assessment of the patient’s readiness for extubation is essential as well. I utilize full ventilatory support all the way to extubation so that if laryngospasm or poor ventilator effort is encountered, the patient will have the physiologic resilience to tolerate this interruption in ventilation and oxygenation.

Dr Gil: For the smoothest extubation, my favorite method is:

Use 2 mL of 2% lidocaine plus 3 mL of 8.4% sodium bicarbonate (NaHCO3) to inflate the ETT (a study found 58% less coughing, 14%-17% less hemodynamic rise12). If needed, add more NaHCO3 to keep the cuff pressure at 22 to 32 cm of water (H2O). Consider refilling after 6 hours.

At 20 to 30 minutes surgical time left: If using muscle relaxant, maintain at 1 to 2 good twitches on the train of four, even if half doses are needed. Change to 6 breaths per minute (BPM; to raise carbon dioxide) and 5 cm H2O positive end-expiratory pressure (PEEP).

10 to 15 minutes left: If nitrous oxide (N2O) acceptable: Turn off agent and/or propofol. Alter flow to N2O:O2 (6:2 L/min). Simultaneously, taper the remifentanil maintenance dose every 5 minutes to reach 0.05 mcg/kg per minute. Other narcotics need to be stopped earlier.

If N2O contraindicated: Taper inhalation (at higher gas flows) and/or propofol to reach one-fourth to one-third of maintenance with 10 minutes left, and none at 5.

10 minutes left: Give lidocaine 1.5 mg/kg for signs of “lightness” or 2 to 8 minutes before extubation. Ten minutes after the first lidocaine dose, give half as much, if needed, to extend effect.

Begin pressure support ventilation at 6 BPM and 5 cm H2O continuous positive airway pressure (CPAP) at any time in the final 5 to 10 minutes. If BPM is greater than 6 and end-tidal gases are one-sixth the minimum alveolar concentration, switch to spontaneous ventilation with 5 cm H2O CPAP.

2 minutes left: As needed, give full muscle relaxant reversal. Suction the oropharynx toward the larynx immediately or 2 minutes after lidocaine. If necessary, suction the ETT. If using N2O, stop. Place a nasal cannula. Only in older, sicker, cerebrally impaired, or too sleepy patients, taper remifentanil downward, even to zero.

For easy airway patients: After seeing good spontaneous ventilation and low current sustained tetanus, as soon as the patient makes a semipurposeful movement (even raising eyebrows—ie, not a reflex) in response to a command, extubate. Stop remifentanil.

For difficult airway patients: Position them head up, if possible, with antihypertensives ready. When much more alert and fully responsive to commands, extubate. Stop remifentanil.

Changing to an SGA when deep is good, although occasionally difficult.

Dr Hodgson: Exchange the ETT for an SGA device, preferably second generation (LMA Supreme [Teleflex] or i-gel).

I have not had success with low-dose remifentanil infusion.

Cook Medical now has a staged extubation kit with a tapered airway exchange catheter (AEC) that can remain in place until airway obstruction can be excluded. The AEC can be removed within 10 minutes, if the airway is clear, but the guidewire can be left in situ in case of cardiorespiratory deterioration for up to 24 hours.

Dr Nekhendzy: Besides deep extubation, which is almost never performed in my (predominantly) head and neck anesthesia practice, smooth extubation strategies include the use of SGA as the primary ventilatory device in lieu of the ETT, the ETT-SGA exchange at the end of the case (the Bailey maneuver), and a pharmacologic approach involving the use of opioids, particularly remifentanil to blunt the tracheal responses.

The Bailey maneuver involves, in steps, insertion of the SGA device (usually, the LMA) behind the existing ETT with the patient still adequately anesthetized, removal of the ETT, and administration of the ventilatory support through the SGA until the patient resumes spontaneous ventilation and awakens from anesthesia.

Remifentanil provides a predictable, rapid, and almost simultaneous recovery of consciousness and protective airway reflexes, while also blunting sympathetic responses associated with extubation. For TIVA, a target concentration of remifentanil 1.5 to 2.1 ng/mL, corresponding to a manual infusion rate of 0.05 to 0.07 mcg/kg per minute, is usually sufficient.13-15

For balanced desflurane and sevoflurane anesthesia, the effect-site concentration of remifentanil in 95% of adults (EC95) for blunting tracheal reflexes is higher, ranging between 2.3 and 2.9 ng/mL,16-18 which corresponds to the manual infusion rate of 0.08 to 1.0 mcg/kg per minute. The target concentrations for both TIVA and inhalational anesthetics will be lowered depending on the amount of other opioids used.

Prof O’Sullivan: Low-dose remifentanil infusion is best. This involves stopping the inhalation agent, etc, at the end of the procedure and very gradually reducing the remifentanil infusion. It is not quicker, but patients wake without coughing and tolerate the ETT. I also use the Bailey maneuver, but only if there has been no intraoral surgery. This involves exchanging the ETT for a laryngeal mask airway (LMA) while the patient is still paralyzed and asleep. Occasionally, in very high-risk extubations, I would use a Cook Medical Staged Extubation Set, and leave the AEC in situ for a while until the patient is fully awake and the airway is safe.

Dr Perin: For gentle extubation, I distinguish the difficult airway from the easy airway. In patients with easy airways, I normally use remifentanil continuously in a dose that permits the patient to open his or her eyes when called by name (0.3-0.5 ng/mL TCI), and I give lidocaine 1.5 mg/kg IV 10 minutes before extubating.

On the other hand, for patients with a difficult airway, I prefer to extubate with an AEC, while being cautious not to introduce too far or using the Bailey maneuver, using a classic laryngeal mask with continuous remifentanil.

Dr Urdaneta: The transition from intubation to extubation and from an anesthetized to an awake state should proceed as smoothly as possible in all cases, but it is especially important for certain populations and after certain surgical procedures.

Except for cases of airway fire, extubation is entirely an elective procedure that requires proper preparation and planning. Gentle removal of the tube and transition to either room air or administration of supplemental O2 are essential for a smooth transition. There are multiple ways to minimize the stimulation effects of the tracheal tube during extubation:

Some advocate removal of the tube while the patient is still anesthetized and before the return of tone and reflexes, called the “sleep” method. In my opinion, the benefits with regard to smooth transition and lack of stimulation by the tracheal tube are neutralized by a higher incidence of airway obstruction, so personally, I do not perform sleep extubation.

In my practice, I perform extubation after the return of airway reflexes, muscle tone, and respiratory drive (the “awake” method), and consider this method safer because patients maintain their own airway. In order to offset the higher stimulation and associated effects by the presence of the tube, I used to administer lidocaine either topically or intravenously, and even attempted cuff administration, but I was not impressed by the results. Since the availability of remifentanil, I started using an infusion administered at the end of the procedure and turned off other anesthetic agents, reversed muscle relaxants, and positioned the patient with the head elevated at least 30 degrees, at which point I turn off the infusion and allow the patient to transition and start breathing spontaneously. Once they open their eyes and respond to commands, I remove the tube. In some cases, specifically head and neck operations, I also practice and recommend performing the tracheal tube–SGA exchange (Bailey maneuver). This allows me to have a patent airway with low or minimal stimulation, and this translates into a smooth transition from intubation to extubation with less chance of altered responses from the presence of the tracheal tube. However, this is an advanced technique that requires practice and familiarity, and should be avoided in patients at risk for aspiration of gastric contents. It is also very important to ensure a deep plane of anesthesia when the exchange of the tube is taking place.

3. Some authorities argue against the use of Sellick’s maneuver during a “rapid sequence induction (RSI),” stating that it does not always prevent aspiration, it does not improve intubation success rates, and it distorts the laryngopharyngeal landmarks. What is your take on this controversy?

Dr Brainard: It is well known that aspiration is a significant and severe adverse event, however I do not believe that the application of cricoid pressure (CP) has ever been shown to correlate with aspiration rate. I am not aware of any convincing evidence that it decreases the risk in any patient group, no matter how “expertly” it is performed.

I do believe it occasionally decreases the quality of the laryngoscopy view, frequently makes extralaryngeal manipulation more difficult, and always adds additional complexity to the intubation.

Until there are data that show that this medical intervention improves patient outcomes, I believe the drawbacks of CP exceed the potential benefits.

Prof Cook: NAP4 told us that the most common cause of airway-related death during anesthesia was aspiration,5,6 so I take this topic seriously. My personal view is that a lot of misinformation is spread about cricoid force. When cricoid force is applied correctly (correct position, 1 kg before loss of consciousness, increasing to 3 kg after loss of consciousness), it is likely to obstruct the hypopharynx/upper esophagus, in most cases. At these forces, it does not cause airway distortion, does not interfere with laryngoscopy (indeed may improve the view), and does not obstruct manual ventilation. This is a win-win.

In the circumstance that cricoid force is applied and it is believed that it is interfering with laryngoscopy, or there is a need to insert an SGA device, it can be released or removed with suction at the ready. In my view, the vast majority of problems with cricoid force are caused by poor training and incorrect application. In practical terms, it is still difficult to improve on the concise summary of the topic by Vanner and Asai, from 1999.19 Getting the assistant to practice cricoid force immediately before application, by depressing an air-filled and capped syringe (a 20-mL syringe depressed to ~12 mL or a 50-mL syringe to ~32 mL) dramatically increases the likelihood of correct performance.20 Of note, NAP4 reported fatalities from cases where RSI was indicated but not used, but none where the use of RSI led to severe morbidity.

Dr Doyle: In Sellick’s original 1961 study, of the 26 cases at regurgitation risk, there were 3 cases of immediate regurgitation upon the release of CP. This suggests that the method sometimes certainly works. Still, the evidence for its universal application in patients at risk (ie, making it a standard of care) is a bit flimsy. Additionally, the number of reports of CP causing injury or harm has become substantial.21,22 As a consequence, many clinicians no longer view CP as a standard of care in patients at risk. Perhaps Maltby and Beriault23 summarized the issue best: “If cricoid pressure makes laryngoscopy difficult, and manipulation of the airway under light anesthesia provokes gagging and vomiting, its indiscriminate use may cause real problems while trying to solve hypothetical ones. It should be reserved for cases at genuine higher risk, like those mentioned by Sellick in his study.”

Dr DuCanto: My simple answer to this question is that I am not going to advise anyone to abandon the use of CP during RSI; however, I have abandoned the use of this maneuver in my clinical practice. I believe it is a low-yield maneuver with a potential drawback in that it distorts the airway during preoxygenation and ventilation following induction, and it upsets the positioning of the patient during laryngoscopy, essentially partially undoing the effort you make to properly position the patient for optimal laryngoscopy. If the patient has not received an adequate anesthetic before the onset of laryngoscopy, the patient will react in a number of ways, including regurgitation. The key to safe RSI is to adequately anesthetize the patient before airway endoscopy to prevent the reflexes that stimulate regurgitation. So, with CP, is it going to prevent the sequella of active emesis? No way. Will it prevent passive gastric flow from the stomach? Likely yes, it can—but not active flow of emesis, which is the deadly kind.

Dr Gil: While training/practicing at 2 major university centers, I have seen 2 awake intubation patients suffer aspiration, but have never seen an “asleep” aspiration. During training, I always imagined that not every esophageal/hypopharyngeal passage was wholly posterior to the cricoid cartilage. Because of this, for at-risk patients, I always used an alternative 3-digit variation of Sellick’s maneuver instead of the conventional thumb and forefinger force placed only on the cricoid cartilage.

For this variation, apply the thumb and middle finger extremely adjacent to (ie, hugging) the cricoid cartilage on either side, medial to the carotid arteries (Figures 1-2). Simultaneously, keep the forefinger bent and pressed onto the cricoid anteriorly, so that the distal phalanx is perpendicular to the sides, forming a horizontal bridge between the other 2 digits. This generates an equally forceful downward pressure across and lateral to the cricoid cartilage. The pressure has been tested at the Illinois Society workshop and was within the recommended 20 to 44 N of force (~2-4.4 kg•m/sec2).

 

Palpation for pulsation will ensure digit placement is medial to the carotids; however, I would not use this placement if there is any hint of anatomical uncertainty, or if it is not preferable.

Although the overall incidence of aspiration during general anesthetics is small (1-7/10,000),24 it is still reported during application of Sellick’s maneuver. On the other hand, an editorial by Vanner concluded that “cricoid pressure probably is effective at preventing regurgitation at induction of anesthesia,” and cited a number of observational and abstract studies to support this.25 He also cited a court case where “the judge ruled against the anesthetist who did not apply cricoid pressure.”

Although “cricioid pressure” certainly can be helpful, no one has ever advocated using “Sellick’s maneuver” to better the laryngeal view, in contrast to the BURP (backward, upward, rightward pressure) maneuver. If the view worsens, lessening the pressure is acceptable. BURP can be utilized in combination with Sellick’s to improve laryngoscopy without concern that cricoid movement will risk regurgitation.

Dr Hodgson: Cricoid pressure is required for patients at risk for aspiration, particularly with bowel obstruction or trauma soon after a meal. Experienced anesthesiologists will be familiar with the sensation of relief after a patient has been safely intubated with the use of CP when the pharynx fills with feculent material after removal of CP. Some may even have had the experience of intubating without CP and finding the same material filling the pharynx (and tracheobronchial tree) before intubation. Aspiration of feculent material has high morbidity (ICU admission for ventilation) and mortality.

A patient deemed at risk for aspiration should be intubated with CP. The risk for aspiration is controversial, with most patients in pregnancy, after trauma, and with chronic renal failure not having an increased risk. A simple question to define aspiration risk in emergency surgery is, “Are you hungry?” Hunger is indicative of normal GI function, while absence of hunger with some nausea is an indicator of impaired GI function due to physiologic stress and/or administration of opioids.

The alteration of intubating conditions seems to be a problem mainly for inexperienced airway managers with limited opportunities for practice (eg, those in the ED and ICU) and is not a major issue for those intubating regularly (anesthesia).

Dr Nekhendzy: The question is somewhat misleading. Sellick’s maneuver does not guarantee full prevention of aspiration, and was not designed to improve intubation success rate during “crash” induction. Yes, the controversy does exist, largely due to a lack of controlled trials and inadequate training for proper application of CP. As we know, a force of at least 30 N (~3 kg, or 7 pounds) is required for CP to be effective. Poor technique may contribute to many instances of preventable regurgitation and observed airway distortion when CP is applied, making both mask ventilation and tracheal intubation difficult. I would certainly advocate for a momentary CP release if visualization is impaired during direct laryngoscopy (DL).

I have seen the Sellick’s maneuver to be highly effective in both preventing and stopping major regurgitation. To paraphrase Justice Stewart’s words, “you know it when you see it,” and for me, no true CP controversy exists. My clinical observations are in line with the findings by Zeidan et al,26 who have neatly demonstrated a nearly universal occlusion of the esophagus with properly applied CP.

Prof O’Sullivan: Although aware of the controversy and its limitations, I use it in patients of very high risk (eg, bowel obstruction). It is still a standard of care in the United Kingdom and Ireland. However, I have a very low threshold for removal of CP under direct vision with suction on, and regularly do so if there is any difficulty with laryngoscopy. I always remove if placing an LMA following difficulty with laryngoscopy. There is no good evidence that it is effective, or that its application is standardized and, in addition, many countries worldwide do not advocate its use.

Dr Perin: It is quite difficult to make a decision concerning this subject based on the literature and evidence because time goes by and we have yet to come to a conclusion. In my daily practice, I do Sellick’s maneuver not as the only technique but adjuvant to others to protect from aspiration.27 If you have poor glottic visualization, I ask to release it. To prevent this from happening, I prefer the double-hand Sellick’s maneuver instead of the one-hand maneuver.28 If something goes wrong and I did not do the maneuver, the first thing that would come to my mind would be: What if I had done it?

Dr Urdaneta: Considerable controversy surrounding the routine application of CP during RSI exists with polarizing points of view among experts and professional organizations—advocates who consider the application of CP effective in preventing aspiration, and critics who consider it ineffective and perhaps detrimental, given some reports of worsening conditions for laryngoscopy and SGA placement with its use. Truth be told, neither camp is entirely able to confirm or deny the virtues of CP, and maybe they never will be, because there is an insufficient level of evidence and limited knowledge of the physiology and anatomic boundaries of the cricoid cartilage and its relationship to the esophagus. I personally continue to use and document CP for my RSIs, and if I encounter difficulty during the intubation attempt—due to laryngeal malposition or if SGA as a rescue ventilatory device is being hampered by CP—I instruct my assistant to alter or remove it. Fortunately, in my practice, this happens very rarely. Bottom line: CP may not be 100% effective, and it may not be done correctly by the majority of assistants, but given the medicolegal implications for anesthesiologists of an aspiration, it is very difficult to defend omitting CP during RSI in patients at risk for aspiration.

4. When, if ever, do you favor the use of awake tracheal intubation over RSI in patients at high risk for aspirating gastric contents after the induction of general anesthesia?

Dr Brainard: In the ED, most of our patients are at high risk for aspirating gastric contents and most patients are intubated via RSI. I estimate that approximately 5% of ED intubations should be predicted to be at high risk for aspiration and/or be an anatomically very difficult airway. Because of this, my personal view is that awake intubation is clinically indicated in about 5% of ED intubations. As a corollary, I advocate that around 10% of ED intubations should ideally be performed as awake intubations, with around half of them being used for practice.29 This recommendation, of course, depends on the level of skill and experience of the airway team.

Prof Cook: It is difficult to give a generic answer to this question; it is a matter of case-by-case judgment, which happens with the patient in front of me. I am not against the use of awake fiber-optic intubation (AFOI) with a full stomach, but if this is the chosen technique, then the “A” really does need to mean awake (until the tracheal tube is in place and the cuff inflated) to ensure safety. The halfway house of sedation and AFOI is a recipe for disaster. Factors that would make me lean toward AFOI would be those factors strongly predictive of a difficult laryngoscopy, difficult oxygenation, and “composite airway failure” (ie, failure of multiple airway techniques).30 Factors of particular concern to me would include a history of previous airway difficulty or failure, radiation therapy to or burns on the anterior neck, a markedly reduced mouth opening, and gross obesity.

Dr Doyle: As a rule, if the patient at high risk for aspiration looks like he or she might not be straightforward to intubate by ordinary means, I will employ awake tracheal intubation, using only minimal sedation. But even if intubation is expected to be uneventful, I will still sometimes use awake tracheal intubation in full-stomach patients that somehow look “scary”—especially in patients with a small-bowel obstruction—just to be on the safe side. The secret to success, as always with awake intubation, is in good topicalization of the airway.

Dr DuCanto: Two major clinical scenarios favor the use of awake tracheal intubation: severe derangements in airway anatomy and severe derangements in the physiologic/hemodynamic condition of the patient. The airway anatomy answer is a given, but the physiologic/hemodynamic derangement is another matter. If the patient is in septic shock, cardiogenic shock, or hypovolemic shock, the administration of induction agents and positive-pressure ventilation may produce cardiac arrest during induction, with the extra burden of managing emesis (or hematemesis). Resuscitation in such cases is remote, per the landmark study on this topic by Thomas Mort.31 Resuscitation before induction and intubation is required in patients with severe physiologic/hemodynamic derangements, and as such, it makes sense in some of these cases to manage tracheal intubation with the proper use of awake techniques.

Dr Gil: In patients with a high risk for aspiration, awake tracheal intubations are preferred over RSI when the airway is thought to exclude success on the first asleep intubation attempt. This may include the combined factors of high aspiration risk plus virtually absolute categories, such as 1) history of a difficult intubation, 2) history very likely to result in difficult intubation (eg, obesity with significant airway/neck radiation treatments), or 3) an extremely poor finding on airway examination, for example, an adult mouth opening of less than 0.6 cm (eg, near total upper airway obstruction, or massive facial trauma affecting the airway).

Likewise, awake intubations are preferred in patients with a high risk for aspiration plus more than one medium or worse category of potential difficulty noted on the history or airway examination, such as 1) historical problems (eg, moderate obstructive sleep apnea [OSA]), 2) concomitant health issues resulting in intolerance of even short periods of apnea, or 3) likelihood of unsuccessful mask ventilation and/or unsuccessful insertion of an SGA device (eg, multiple airway examination findings that are medium to extremely poor).

Factors can make this medium-or-worse category variable in determining the type of airway management approach (eg, a patient with a Mallampati III score, neck extension of 40 degrees out of 80 to 90 degrees, and an upper lip bite test class II). RSI may be tolerable if the body habitus is good; however, this would not be the case in another patient who is super-obese, depending on the degree of obesity.

Dr Hodgson: In the event of a predicted difficult airway, particularly difficulty with laryngoscopy (including video/optical) and mask ventilation.

Dr Nekhendzy: Never, unless an awake intubation is indicated for an anticipated difficult airway. An awake intubation is not fault-proof for these patients, and may be associated with regurgitation and aspiration, which is documented in case reports.

Many things can go wrong with the awake approach in “full-stomach” patients. The depressed level of consciousness either due to sedation and/or resorptive effect of local anesthetic may predispose patients to aspiration. Retching and gagging occurring during local anesthetic application, or caused by inadequate topicalization during intubation, may provoke regurgitation. The SLN block and TTB in these patients should be avoided to preserve laryngeal and tracheal responses. However, even with careful, targeted local anesthetic delivery (eg, the SAYGO technique), it may be difficult to avoid the suppression of these reflexes altogether. Application of local anesthetics to the upper airway has been shown to invariably depress laryngeal reflexes and function. Finally, inflation of the ETT cuff may provoke massive regurgitation and aspiration if the tracheal reflexes are not blunted properly.

Prof O’Sullivan: I would avoid RSI and do an AFOI if the patient has been assessed as a predicted difficult intubation. Obviously, in this situation I would avoid sedation.

Dr Perin: If I face a patient with signs of a difficult airway, especially signs of difficult or impossible ventilation and a full stomach, I have no doubt I will do an awake intubation. And that is simply because if I can’t intubate the patient on the first try with an RSI, I will need to ventilate with a face mask, and in a patient with a full stomach this can facilitate regurgitation.

On the other hand, if the patients do not have predictive factors of failed ventilation and intubation, I prefer to do an RSI. The key factor on a great number of regurgitations during RSI is that when we administer a neuromuscular blocking agent, we seldom start the chronometer—20 seconds seems like 90 seconds during this stressful situation. When you put the laryngoscope at the vallecula, the patient starts to move in a gag reflex and the abdominal contractions improve the chances of aspiration. Paralyzed patients do not vomit (actively), although they can regurgitate depending on the intragastric pressure. Let’s start our chronometers or use the train-of-four test to be sure the patients are well paralyzed.

Dr Urdaneta: Patients with a high risk for aspiration pose a triple challenge: prevention of regurgitation, prevention of aspiration, and institution of appropriate airway management techniques. Difficult airways—whether from difficult mask ventilation or difficult tracheal intubation with coughing or straining—constitute key conditions for gastric regurgitation and pulmonary aspiration. If there are signs of anticipated difficulty, or history of difficult intubation, placing a cuffed tracheal tube before the administration of general anesthesia and avoiding the vulnerable period that occurs after the loss of consciousness and during attempts at tracheal intubation is the recommended approach. With awake techniques, protective reflexes, muscle tone, airway patency, and gas exchange are maintained; in these patients with difficult airways, therefore, the awake approach is recommended.

5. What is your position on the use of SGA devices in patients undergoing surgery in the prone position?

Dr Brainard: As an emergency medicine consultant, I have no experience with this question.

Prof Cook: The short answer is, I think it is daft.

The longer answer goes like this. I’m a big fan of SGA devices, and they form the backbone of my practice, accounting for approximately 70%. With second-generation SGA devices, I believe we have not reached the limits of what we can do safely. But part of the problem with exploring that boundary is that we only find where it lies by overstepping it and finding something is not safe. Yes, we can anesthetize patients with SGA devices and place them prone, and most will be OK. But just because we can do it does not mean we should do it. The incidence of problems with an SGA device during maintenance is low, but the consequences of such an event when the patient is prone is likely to be significant or even catastrophic. I have done it twice with a well-placed, high-quality, second-generation SGA device in an operation where it was easy to stop and turn the patient supine. But even then, I spent the whole operation thinking, “Why have I done this?” I would ask those considering this to ponder whether such a choice of technique places safety first and is patient- or doctor-centered medicine. Then I’d ask them to explain the pros and cons to the patient and take informed consent.

Dr Doyle: Although I know of clinicians who routinely use second-generation SGA devices in patients with a normal airway undergoing short-duration surgery in the prone position, this is a practice that I nevertheless avoid, as I do not see the benefits overriding the risks. That being said, I would not be overtly critical of someone who practiced this way, especially in cases where the surgeon is able to quickly cover up the wound and assist in placing the patient in the supine position onto an immediately available stretcher. One reason for my mixed position on this question: There is now literature emerging to support this practice.32,33

Dr DuCanto: I have utilized SGA devices in the prone position to facilitate GI endoscopy; however, I had the head of the patient turned to the side to allow access for both myself as well as the endoscopist. I honestly cannot advocate for the use of SGA devices in the prone position, despite my positive experiences with them, other than for rescuing a patient’s airway during sedation cases. There are too many downsides to this technique to recommend this method, since the clinician cannot guard against laryngospasm or the sequela of passive or active emesis during the procedure without a cuffed tracheal tube in the patient’s airway.

Dr Gil: I will never ever recommend the technique of using an SGA device in the prone position—except to rescue an airway in an already-prone patient. My reasoning is the result of only 2 inquiries made to airway management specialists who did use SGA devices while prone—although, frankly, I could have stopped after the first one.

When the SGA devices became problematic in the prone position, these specialists tried to fix them and sometimes succeeded—but not always. Even use of other airway devices including SGA ones may be extremely difficult in this position. However, they also said they usually employed this method only in “normal airway patients for shorter surgeries, but” they “kept the patients’ stretchers nearby in case there was a need for a sudden, rapid return to the supine position to rescue dislodgement or airway loss.”

It was obvious to me that this requires surgeons to be able to immediately stop working and quickly cover the operative field, so that a rapid return to the supine position for airway management could take place. I concluded that elective SGA use in a prone patient does not seem ideal for the patients’ interests, the surgeons’ interests, or my own sanity.

I can better tolerate an SGA device in the lateral position, despite one experience with a thin, “normal airway” earthquake victim with no other problems, when the SGA device ceased to function; happily it was rescued with use of an ever-present video laryngoscope. However, to electively choose to use SGA devices in the lateral position, it would have to be on a thin patient with a “normal airway” with no other problems in a noncomplex, nonvital surgery, in case turning might be needed—particularly, if any of my colleagues had to take over the case.

Dr Hodgson: The use of SGA devices in the prone position is an example of getting away with an inappropriate technique with predictable complications (eg, dislodgement, difficult replacement) rather than providing optimal management with minimization of complications.

Dr Nekhendzy: This is not something that I would routinely do in my practice. I need to find a good reason for abandoning superior control of ventilation and airway protection that is achieved with ETT. A hypothetical example could be a professional singer presenting for a short, minor surgery, and I think I would also want to have buy-in from the surgeon.

A small number of observational trials and case reports have documented the safety and effectiveness of the technique, and the advantages for the patient, such as assuring proper, comfortable positioning before induction. If I were to do it, I would certainly use a second-generation SGA device with the gastric port, and preferably the SGA device with greater ventilating capability, such as the LMA ProSeal. I would also have all the contingency airway plans in place during induction of anesthesia.

Prof O’Sullivan: I think this is absolutely contraindicated. Just because you can, does not mean you should. There are predictable complications, which are life-threatening.

Dr Perin: I do not use SGA devices in the prone position because I don’t feel confortable. What if the patient has a bronchospasm during the procedure that is difficult to treat and you are not able to ventilate because of a leak? What if you have an anaphylaxis during the procedure? Just because you can, doesn’t mean you should do all the techniques. We have some papers on the subject, but I think we need to find the limits for these devices.

Dr Urdaneta: There is some debate whether SGA devices should be used in surgical procedures in the prone position. Personally, I have never done an elective prone case with an SGA device in place, and therefore I admit personal bias. My opinion is that current available reports of success with this technique answer whether SGA devices can be used in certain short procedures and in selected low-risk patients, but do not answer the more important question of whether we should be using SGA devices in the prone position. Available limited evidence by those who use the technique find that this is a safe procedure; however, I am not convinced there is enough evidence to elucidate which patients benefit the most and on which surgical cases they should be used, and more importantly, in which cases the technique should be avoided. In my current practice, the only place for SGA use in prone cases is for rescue purposes, but as with everything, I am open for a change in the future if evidence points to any real advantages for elective use of SGA devices in these cases.

6. What is your position on the use of SGA devices in very obese patients undergoing surgery?

Dr Brainard: As an emergency medicine consultant, I have no experience with this question.

Prof Cook: My previous answer touches on this. Safety has to be our first priority. Obesity is only one factor to consider when choosing the airway—others include other comorbidities, the presence of gastroesophageal reflux disease (GERD), the type of surgery, the surgeon, the duration of surgery, access to the airway during surgery, the necessity for controlled ventilation, etc—and the anesthetist’s experience and skill. As I described above, my practice is based on use of SGA devices, and I restrict myself to one second-generation device (except for the flexible LMA for head and neck work), but I am cautious about pushing boundaries. I will use an LMA ProSeal for a brief knee arthroscopy in a patient with a body mass index (BMI) of 38 to 40 kg/m2 without other comorbidities, but I would be unlikely to use it for a laparoscopic cholecystectomy or in the lithotomy position in someone with a BMI much above 30 kg/m2. When using an SGA device in a patient with a higher BMI, I will pay particular attention to insertion and to the specific tests of anatomic position and function before proceeding. If the device is not operating optimally, I will revert to intubation. Another important factor in this situation is the experience of the anesthetist in using the specific device. My practice has evolved though use of one second-generation SGA device in thousands of patients, and it is only through that experience that I have developed the knowledge and confidence to safely expand the uses of the device. Brimacombe recognized a learning curve with the same device of up to 750 cases.34 SGA devices are very safe and highly versatile devices, but those inexperienced in their use should start on lower-risk cases and expand their practice as their skills increase.

Dr Doyle: I do not electively use SGA devices in very obese patients. I recognize, however, that some second-generation SGA devices such as the LMA ProSeal are better suited to obese patients than earlier products. Furthermore, many clinicians outside of North America are quite comfortable using SGA devices in obese patients who lack other comorbidities and are undergoing short-duration procedures involving minimal physiologic trespass (eg, carpal tunnel surgery).35 In the final analysis, then, a decision whether or not to use an SGA device in the very obese patient will depend on factors such as the anticipated benefits, one’s clinical experience, the nature and duration of the surgery, the degree of physiologic trespass involved, and the kind of help that is available should difficulties arise.

Dr DuCanto: SGA devices can be very useful for this type of patient, provided that an SGA device is a reasonable choice for the planned surgical procedure, and that the procedure is of a relatively short duration (<1 hour). Should the surgical procedure plan require a long anesthetic time (>1 hour), nondepolarizing muscle relaxants with positive-pressure ventilation, or a change in position to the lateral position, I would not advocate the use of an SGA device in these patients, with the exception of their use to facilitate tracheal intubation with a flexible bronchoscope or an optical or video stylet.

Dr Gil: Concerns with plans for SGA usage in very obese patients depend on:

the degree of obesity—higher degrees of obesity may make ventilation through the SGA device difficult due to the restrictive effect;

concomitant historical difficult airway factors such as severity and cause of OSA (eg, excessive lingual tonsillar material) may make SGA ventilation impossible;

O2 deprivation intolerance in the face of a difficult SGA placement, since obesity is associated with smaller functional residual capacity and increased rates of desaturation with apnea, other factors could compound the situation;

risks for aspiration—while second-generation SGA devices are designed to avoid aspiration, no randomized double-blind study has proven that their use is significantly better than RSI;

effects of surgery on the patient’s ventilation—intrathoracic or intraabdominal surgeries are more prone to worsen restrictive effects on respiration;

duration of the surgery—longer hours are more associated with side effects from SGA use, such as nerve injuries and so forth;

patient positioning (eg, lithotomy or reverse Trendelenburg, both of which have a negative restrictive effect on ventilation); and

airway examination results, with regard to ease of mask ventilation, SGA insertion, and intubation.

In unfavorable situations having more than very minimal concerns, I would not recommend using an SGA device, except to rescue someone’s airway.

Dr Hodgson: Obese patients may benefit from airway management using SGA devices, provided that adequate tidal volumes (6-8 mL/kg ideal body weight [25×height2]) can be delivered without leak. This is facilitated by the use of second-generation devices (i-gel, LMA ProSeal) and the use of lateral tilt, usually to the left, as well as elevation of the head of the bed to reduce upward pressure on the diaphragm.

Dr Nekhendzy: Again, there should be a good reason for me to use it as a stand-alone ventilatory device. The NAP4 findings have demonstrated frequent mismanagement of obese patients with SGA devices, and aspiration of gastric contents as a major cause for airway management–related morbidity and mortality.

That said, I have safely used second-generation SGAs as primary ventilatory devices for morbidly obese patients without a history of significant GERD, and even without immediate access to the patient’s airway, with the OR table turned 180 degrees. In my practice, which is predominantly head and neck anesthesia, I find SGA devices highly beneficial for promoting smooth awakening after certain procedures (eg, otologic surgery, functional endoscopic sinus surgery [FESS], and facial cosmetic surgery).

Similar to my answer to question 5, and in line with the NAP4 findings, for obese patients I would prefer a second-generation SGA device. I would most commonly reach for the LMA ProSeal, whenever feasible. Of note, I would use it almost exclusively for otologic procedures (eg, middle ear surgery), where there is no device interference with surgical access, and where the patient’s head is not manipulated until surgery is completed. I would not use LMA Flexible (Teleflex) for FESS, other intranasal, or facial procedures in morbidly obese patients, and would universally intubate them.

If I do use second-generation SGA devices for morbidly obese patients, I always take certain steps to ensure patient safety, such as pharmacologic prophylaxis against aspiration before induction when indicated, documenting proper SGA positioning through a battery of tests, and ensuring a sufficiently high airway seal pressure, absence of gastric insufflation with positive-pressure ventilation, and proper tidal volume with a small leak fraction before turning the patient over to the surgeon.

Prof O’Sullivan: I would use second-generation SGA devices in these patients, but it would obviously depend on other factors including the BMI, comorbidities, the surgery planned (position), and the duration of surgery. I would need to ensure adequate ventilation. For obese patients with anticipated difficult airways and/or those undergoing prolonged surgery, I frequently place LMAs in an awake patient with topical local anesthesia. Then I intubate through the LMA with the fiber-optic scope–Aintree catheter combination and use SAYGO. I then railroad the ETT over the Aintree catheter (the technique is described pictorially on the Difficult Airway Society’s website). This allows oxygenation throughout the process and is a safe and comfortable awake technique for the patient.

Dr Perin: The SGA devices are an option in obese and very obese patients, and I feel very comfortable using them. What rules my choice are the procedure and the patient’s comorbidities. For example, if the patient has severe GERD or is a chronic user of opioids, I don’t use SGA devices, not even second-generation ones. The key point is to start the surgery only after you are comfortable with the ventilation; if this never comes, do not hesitate to change for an ETT.

Dr Urdaneta: I believe this question requires some clarification, because not all types and degrees of obesity, not all surgical procedures, and not all SGA devices are the same or belong in the same category. As the question was asked broadly, I am going to answer in the same fashion. With regard to obesity, as time has passed and I have gained more experience, and, more importantly, since becoming more familiar with the use of second-generation SGA devices in my practice, my degree of comfort with the use of them in this patient population has increased to a current cutoff point of a BMI of about 40 kg/m2. Patients need to adhere to American Society of Anesthesiologists (ASA) nothing by mouth (ie, preoperative fasting) guidelines and must have no history of GERD, or if they do have GERD, it must be under control. With regard to types of procedures and duration of surgery, I prefer to use them in procedures where the head is going to be in a neutral position, close to the anesthesia machine and not in an extreme bed inclination. Personally, the only laparoscopic procedure I have done with an SGA device has been postpartum tubal ligation. My current cutoff of the use of an SGA device with regard to case duration is an arbitrary duration of 4 to 6 hours, admitting that my comfort after 4 hours diminishes progressively.

7. When intubating very obese patients, what special steps do you take?

Dr Brainard: In addition to the anatomic difficulties posed by obesity, rapid deoxygenation is a serious concern. Adequate preoxygenation and apneic oxygenation are essential and best described by Weingart and Levitan.36 In the ED, this typically means at least three minutes preoxygenation with a tightly fitted bag-valve mask with 15 L per minute of O2, and with 15 cm H2O of PEEP placed over a standard nasal cannula providing an additional 15 L per minute of O2.

Obviously, all the “standard” best practices should also be employed: proper team preparation and planning; a low threshold for hyperacute VL and/or flexible fiber optics; consideration of awake intubation; appropriately large doses of sedatives and paralytics; and immediate access to SGA, surgical, and other rescue airway tools.

For both anatomic and physiologic reasons, careful positioning is key. Patients should be ramped (using noncompressible blankets, not fluffy pillows), their ears should be at least parallel with their sternal notch, their head elevated, and their face parallel to the ceiling. While I believe this careful attention to patient positioning has long been advocated in anesthesia practice, it is still not universally accomplished in ED, prehospital, and ICU settings.

Prof Cook: This is all about oxygenation. Preparation for success starts with preparation for failure. An airway strategy for management of difficult, prolonged, or failed intubation should be in place and communicated to all those involved with intubation. The rescue strategy should focus on oxygenation, while the patient is awakened. For particularly high-risk cases, the patient should be informed of the risk for failure and waking. The literature is conflicting about whether obesity is an independent risk factor for difficult laryngoscopy and intubation (it probably is, but only modestly37), but absolutely clear that obesity is a risk for hypoxia and death during airway management.5,6 Preoxygenation needs to be thorough. Continuing O2 delivery during airway instrumentation—whether with simple low-flow nasal prongs or with high-flow nasal CPAP—currently lacks clear evidence of benefit, but is unlikely to be harmful. Position is important, with the anti-Trendelenburg position improving safe apnea times and ‘ramping’ improving laryngoscopy positions for those with the highest BMIs. The first intubation attempt is the most important, so with optimal head and neck position, adequate anesthesia, and full muscle relaxation, I will perform laryngoscopy as soon as the relaxant has worked. In my practice, this will always be with a video laryngoscope—initially with a Macintosh-style blade, but ready to switch to a curved blade and styletted tube at the first hint of difficulty. And if I fail, then I go directly into my pre-prepared and communicated strategy.

Dr Doyle: First, have extra skilled help in the room as well as advanced airway equipment (ie, a difficult airway cart) immediately available.

Second, position the patient in the “head elevated laryngoscopy position” (HELP).38

Third, provide generous preoxygenation before induction as well as oxygenation via nasal prongs during the laryngoscopy.

Fourth, I favor VL over DL in such cases.

Dr DuCanto: First, I take the extra time to position these patients in a “ramped” configuration, either using the operating table controls to elevate the head of the bed 25 to 30 degrees, or using a commercially available positioning pillow stocked in my department (a large foam wedge) to achieve similar changes in patient position.

Second, utilizing the pressure support and PEEP modes on our modern anesthesia machines, I optimize preoxygenation with a biphasic positive airway pressure (BiPAP) mode to ensure optimal lung recruitment before induction, and I utilize the clinical information from the gas analyzer to achieve an end-tidal O2 concentration of at least 88% to ensure thorough nitrogen washout.

Third, the in-room availability of SGA devices and VL resources is essential in these cases, regardless whether they are utilized or not. The key here is to minimize the endoscopy time (ie, minimize the apnea time) and minimize the delays in gathering resources to secure the airway should an initial attempt at airway management prove unsuccessful. Should an initial attempt at DL (or VL) prove unsuccessful, the clinician must instantly assess the adequacy of face mask ventilation (FMV) with a properly sized oral airway, and convert to ventilation with an SGA device should FMV prove exceedingly difficult or impossible. The key here is to minimize the apnea time in these patients as much as possible. If a patient has attributes that suggest that they will be difficult to ventilate with a face mask, it is reasonable and prudent to place an SGA device initially after induction to optimize ventilation before your first attempt at tracheal intubation. Should the first attempt at tracheal intubation prove fruitless, the SGA device is again inserted into the patient’s pharynx, and the patient is ventilated while the endoscopist carefully assesses the cause of intubation failure and the backup methods to manage the patient’s airway.

Dr Gil: I obtain maximal information from the patient, housemates, records, and prior staff, including the airway examination. I fully inform the patient of management plans while giving reassurance and glycopyrrolate. Difficult airway equipment must be available. I employ monitoring, nasal cannula O2, and an ETT a half size smaller.

For awake approaches, excellent airway anesthesia plus small doses of ketamine, dexmedetomidine, and/or midazolam ensure optimal ventilation/oxygenation. Commonly, I obtain assistance with an intubating oral airway, tongue pull, and jaw thrust for flexible fiber-optic intubation in an upright position.

If intubation under general anesthesia has an excellent chance of success, but I have the smallest doubt, I discuss the possibility of presurgical reawakening followed by awake intubation (a rarity). I use a “backup” position with the external auditory meatus level with the sternal notch, a donut for stability, and folded blankets to maximize neck extension.

Then I oxygenate for several minutes via a face mask with head straps; 20 cm H2O CPAP is continued until relaxation is sufficient for intubation. I have a GlideScope (Verathon) and styletted ETT ready. Assuming no other concerns, I give 1.5 mcg/kg of fentanyl, 1.5 mg/kg of lidocaine, 1.3 mg/kg of propofol, and 0.6 mg/kg of succinylcholine in quick succession. This quick succession of propofol and succinylcholine has less chance of desaturation in contrast to giving propofol, determining if FMV is successful, and then—if not—giving succinylcholine and having to wait for its effect to improve FMV chances. The low-dose succinylcholine optimizes conditions for FMV, provides equivalent intubation relaxation to 1 mg/kg of succinylcholine,39,40 and permits a 90-second shorter duration at the adductor pollicis, improving the likelihood of early diaphragmatic recovery should FMV fail. When asleep, I immediately insert an oropharyngeal airway and institute FMV, while watching the neuromuscular block monitor for fade. An alternative is 1.2 mg/kg of rocuronium if sugammadex (Bridion, Merck) reversal is readily available.

If FMV succeeds, I give 0.7 mg/kg of propofol and intubate.

If intubation fails, as long as FMV is easy, a good plan B can be used.

If FMV is unsuccessful, I intubate.

If intubation fails, an attempt at assisted FMV is likely to be more successful because of the faster resumption of spontaneous ventilation.

Failure of both FMV and intubation will result in the reawakening plan, as described.

Dr Hodgson: I administer premedication with a proton pump inhibitor and sodium citrate; appropriate equipment, especially a heavy-duty table; strict attention to positioning; and a low threshold for awake intubation. Also, minimization of opioid administration and early mobilization.

Dr Nekhendzy: These steps would include pharmacologic prophylaxis against aspiration before induction, full preoxygenation with CPAP of 10 to 15 cm H2O, and proper patient positioning for the intubation strategies chosen.

As a general rule, for morbidly obese patients I want to have backup strategies for both ventilation and tracheal intubation. For the former, I would use a second-generation SGA device, or LMA Fastrach (Teleflex), and for the latter, VL. For the second-generation SGA device, I always use a gum-elastic bougie-assisted technique of insertion, to ensure immediate proper positioning of the device and to be able to decompress the patient’s stomach. On the other hand, LMA Fastrach is very effective in morbidly obese patients for ventilation, airway protection, and blind tracheal intubation, and I use it frequently as a first choice immediately after induction.

For laryngoscopy, I rarely use full HELP patient positioning, as I no longer use DL as a primary technique in these patients. My technique of choice is VL. If VL is unsuccessful, I immediately switch over to an SGA device, per above, to provide optimal oxygenation before a second intubation attempt. For complex cases, I usually have a fully stocked difficult airway cart in the room, in case I need to perform the SGA–ETT exchange using the Aintree Intubation Catheter (Cook Medical), or if I need fiberoptic assistance to intubate through LMA Fastrach.

Prof O’Sullivan: I premedicate with an antacid and proton pump inhibitor. I optimize positioning with aids (eg, an Oxford pillow) and an appropriate table and equipment. I use apneic preoxygenation with humidified high-flow O2 via nasal cannulas. I would consider awake fiber-optic intubation with remifentanil. The video laryngoscopes should be available if the plan is an RSI (for which I would use rocuronium with sugammadex, if available). Also, I would use second-generation SGA devices and intubate through.

Dr Perin: The first step is to put the patients in the sniffing position, and then preoxygenate adequately. I do it with the 25 degrees head-up position.41 If in doubt about FMV, and taking into account Langeron’s and Kheterpal’s criteria, I would do an awake intubation. If not, induction with a neuromuscular blocking agent and VL is the first choice to slightly improve the chances the first time.

The real problem is to plan what to do in the case of a failed intubation or ventilation. At this point, you need to have an SGA device lubricated and ready for use, and if it fails, leave a cricothyroid kit nearby. If you think the case is very challenging, identify and mark the cricothyroid membrane in advance before starting the case.

Dr Urdaneta: I think morbidly obese patients can be very challenging in many aspects of medical care due to associated comorbidities, including OSA. Before getting into the steps of the intubation process, a complete evaluation and physical examination of these patients are recommended; although not applicable universally, morbidly obese patients are usually difficult to mask ventilate, difficult to intubate, and are prone to aspiration of gastric contents. These patients also have altered pulmonary physiology with low functional residual capacity and low O2 reserve, and therefore their peripheral capillary O2 saturation will fall rapidly, even after short periods of apnea. Personally, I follow the ASA difficult airway algorithmic approach and individualize whether the patient needs awake versus sleep intubation.

If the decision-tree approach has led me into the nonawake branch, there are two key factors to consider: First, position the patient with the head, upper body, and shoulders elevated, the so-called HELP position, using OR beds or commercially available devices, and even blankets or towels. Second, actively pursue opportunities to deliver supplemental O2 during the airway management process; this includes proper patient preoxygenation, with or without positive pressure (CPAP or BiPAP). I also continue with the administration of O2 at high flows (15 L/min) via nasal cannulas to extend “safe apnea” during the intubation phase—also called nasal oxygenation during efforts to secure the tube. We currently do not have newer commercially available devices in the OR capable of delivering humidified O2 at higher flows via specialized nasal cannulas, but would use them if they were available in order to take advantage of apneic oxygenation with high-flow humidified O2 delivery.

References

Webb AR, Fernando SS, Dalton HR, et al. Local anesthesia for fibreoptic bronchoscopy: transcricoid injection or the “spray as you go” technique? Thorax. 1990;45(6):474-477.

Gupta B, Kohli S, Farooque K, et al. Topical airway anesthesia for awake fiberoptic intubation: comparison between airway nerve blocks and nebulized lignocaine by ultrasonic nebulizer. Saudi J Anaesth. 2014;8(1):S15-S19.

Kundra P, Kutralam S, Ravishankar M. Local anaesthesia for awake fibreoptic nasotracheal intubation. Acta Anaesthesiol Scand. 2000;44(5):511-516.

Graham DR, Hay JG, Clague J, et al. Comparison of three different methods used to achieve local anesthesia for fiberoptic bronchoscopy. Chest. 1992;102(3):704-707.

Cook TM, Woodall N, Frerk C. Major complications of airway management in the UK: results of the 4th National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: anaesthesia. Brit J Anaesth. 2011;106(5):617-631.

Cook TM, Woodall N, Harper J, et al. Major complications of airway management in the UK: results of the 4th National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 2: intensive care and emergency departments. Brit J Anaesth. 2011;106(5):632-642.

Elliott DS, Baker PA, Scott MR, et al. Accuracy of surface landmark identification for cannula cricothyroidotomy. Anaesthesia. 2010;65:889-894.

Aslani A, Ng SC, Hurley M, et al. Accuracy of identification of the cricothyroid membrane in female subjects using palpation: an observational study. Anesth Analg. 2012;114(5):987-992.

Drummond JC. Airway anesthesia: the toothpaste method. Can J Anaesth. 2000;47:94.

Nair I, Bailey PM. Use of the laryngeal mask for airway maintenance following tracheal extubation. Anaesthesia. 1995;50(2):174-175.

Difficult Airway Society Extubation Guidelines Group, Popat M, Mitchell V, Dravid R, et al. Difficult Airway Society guidelines for the management of tracheal extubation. Anaesthesia. 2012;67(3):318-340.

Estebe J, Dollo G, Le Corre P, et al. Alkalinization of intracuff lidocaine improves endotracheal tube-induced emergence phenomena. Anesth Analg. 2002;94(1):227-230.

Nho JS, Lee SY, Kang JM, et al. Effects of maintaining a remifentanil infusion on the recovery profiles during emergence from anaesthesia and tracheal extubation. Br J Anaesth. 2009;103:817-821.

Lee B, Lee JR, Na S. Targeting smooth emergence: the effect site concentration of remifentanil for preventing cough during emergence during propofol-remifentanil anaesthesia for thyroid surgery. Br J Anaesth. 2009;102:775-778.

Kim H, Choi SH, Choi YS, et al. Comparison of the antitussive effect of remifentanil during recovery from propofol and sevoflurane anesthesia. Anaesthesia. 2012;67:765-770.

Cho HB, Kim JY, Kim DH, et al. Comparison of the optimal effect-site concentrations of remifentanil for preventing cough during emergence from desflurane or sevoflurane anaesthesia. J Int Med Res. 2012;40:174-183.

Choi EM, Park WK, Choi SH, et al. Smooth emergence in men undergoing nasal surgery: the effect site concentration of remifentanil for preventing cough after sevoflurane-balanced anesthesia. Acta Anaesthesiol Scand. 2012;56:498-503.

Jun NH, Lee JW, Song JW, et al. Optimal effect-site concentration of remifentanil for preventing cough during emergence from sevoflurane-remifentanil anesthesia. Anaesthesia. 2010;65:930-935.

Vanner RG, Asai T. Safe use of cricoid pressure. Anaesthesia. 1999;54(1):1-3.

Parry A. Teaching anaesthetic nurses optimal force for effective cricoid pressure: a literature review. Nurs Crit Care. 2009;14(3):139-144.

Brimacombe J, Berry A. Cricoid pressure in chaos. Anaesthesia. 1997;52(9):924-926.

El-Orbany M, Connolly LA. Rapid sequence induction and intubation: current controversy. Anesth Analg. 2010;110(5):1318-1325.

Maltby JR, Beriault MT. Science, pseudoscience and Sellick. Can J Anaesthesia. 2002;49(5):443-447.

Nellipovitz DT, Crosby ET. No evidence for decreased incidence of aspiration after rapid sequence induction. Can J Anaesthesia. 2007;54(9):748-764.

Vanner R. Cricoid pressure. Int J Obstet Anesth. 2009;18(2):103-105.

Zeidan AM, Salem MR, Mazoit JX, et al. The effectiveness of cricoid pressure for occluding the esophageal entrance in anesthetized and paralyzed patients: an experimental and observational glidescope study. Anesth Analg. 2014;118:580-586.

Turgeon AF, Nicole PC, Trepanier CA, et al. Cricoid pressure does not increase the rate of failed intubation by direct laryngoscopy in adults. Anesthesiology. 2005;102(2):315-319.

Brock-Utne JG. Is cricoid pressure necessary? Editorial. Paediatr Anaesth. 2002;12(1):1-4.

McNarry AF, Dovell T, Dancey FM, et al. Perception of training needs and opportunities in advanced airway skills: a survey of British and Irish trainees. Eur J Anaesthesiol. 2007;24(6):498-504.

Cook TM, MacDougall-Davis SR. Complications and failure of airway management. Br J Anaesth. 2012;109(suppl 1):i68-i85.

Mort TC. The incidence and risk factors for cardiac arrest during emergency tracheal intubation: a justification for incorporating the ASA Guidelines in the remote location. J Clin Anesth. 2004;16:508-516.

Taxak S, Gopinath A, Saini S, et al. A prospective study to evaluate and compare laryngeal mask airway ProSeal and i-gel airway in the prone position. Saudi J Anaesth. 2015;9(4):446-450.

Sharma B, Sood J, Sehgal R, et al. ProSeal laryngeal mask airway™ insertion in the prone position: optimal utilization of operation theatre personnel and time?J Anaesthesiol Clin Pharmacol. 2014;30(2):177-182.

Brimacombe J. Analysis of 1500 laryngeal mask uses by one anaesthetist in adults undergoing routine anaesthesia. Anaesthesia. 1996;51(1):76-80.

Timmermann A, Bergner UA, Russo SG. Laryngeal mask airway indications: new frontiers for second-generation supraglottic airways. Curr Opin Anaesthesiol. 2015;28(6):717-726.

Weingart SD, Levitan RM. Preoxygenation and prevention of desaturation during emergency airway management. Ann Emerg Med. 2012;59(3):165-175.e1.

Lundstrøm LH, Møller AM, Rosenstock C, et al. High body mass index is a weak predictor for difficult and failed tracheal intubation: a cohort study of 91,332 consecutive patients scheduled for direct laryngoscopy registered in the Danish Anesthesia Database. Anesthesiology. 2009;110(2):266-274.

Levitan RM, Mechem CC, Ochroch EA, et al. Head-elevated laryngoscopy position: improving laryngeal exposure during laryngoscopy by increasing head elevation. Ann Emerg Med. 2003;41(3):322-330.

Naguib M, Samarkandi A, Riad W, et al. Optimal dose of succinylcholine revisited. Anesthesiology. 2003;99(5):1045-1049.

Kopman A, Zhaku B, Lai K. The “intubating dose” of succinylcholine: the effect of decreasing doses on recovery time. Anesthesiology. 2003;99(5):1050-1054.

Dixon BJ, Dixon JB, Carden JR, et al. Preoxygenation is more effective in the 25 degrees head-up position than in the supine position in severely obese patients: a randomized controlled study. Anesthesiology. 2005;102(6):1110-1115.