The Role of the Supraglottic Airway in Neurosurgery

Posted on by Dr Clemens

Irene P. Osborn, MD

Associate Professor of Clinical Anesthesiology
Director, Division of Neuroanesthesia
Albert Einstein/Montefiore Medical Center
Bronx, New York

Sara Aljohani, MD

Fellow in Neuroanesthesia
Albert Einstein/Montefiore Medical Center
Bronx, New York

The authors reported no relevant financial disclosures.

Airway management in neurosurgical patients can be a perplexing endeavor. In achieving and maintaining a patent airway, it is important to consider its effect on the central nervous system and the well-being of the patient. The evolution of neurosurgical practice and the growth of minimally invasive and diagnostic procedures provide a myriad of clinical challenges.

Introduction

The supraglottic airway (SGA) device is designed for upper airway management, serving as a bridge between face mask ventilation and endotracheal intubation. When blindly inserted into the pharynx, it forms a low-pressure seal around the laryngeal inlet. The SGA device allows ventilation and oxygenation with less stimulation than laryngoscopy and intubation.

The application of this device in the neurosurgical arena is a novel and practical solution. While the SGA device cannot be a substitute for the endotracheal tube (ETT), it can be used in a number of situations where an ETT would have been difficult or impossible to insert. In addition, the beneficial effects on cardiovascular, respiratory, and intracranial reflexes make it a wise choice in certain neurosurgical procedures. This assumes that one is skilled in its placement and manages the anesthetic appropriately. There can be advantages for airway access and maintenance, as well as efficient and safe recovery from anesthesia.

Intracranial Dynamics and Ventilation

The avoidance of hypercarbia is essential in the management of patients with intracranial hypertension. Carbon dioxide dilates the cerebral blood vessels, increasing the volume of blood in the intracranial vault and therefore increasing intracranial pressure (ICP).1 Acute increases in ICP and mean arterial pressure (MAP) during laryngoscopy and endotracheal intubation have been well documented.2

Laryngoscopy and intubation, if performed with difficulty or improperly, can potentially compromise intracranial dynamics and increase morbidity. Both the sympathetic and parasympathetic nervous systems mediate cardiovascular responses to endotracheal intubation. Techniques to blunt this sympathetic response have included:

  • additional doses of thiopental or propofol;
  • use of β-blockers or other antihypertensive agents;
  • use of IV lidocaine; and
  • administration of opioids, such as fentanyl or remifentanil (Ultiva, Mylan), to blunt response.

Esmolol or lidocaine as an IV bolus of 1.5 mg/kg before laryngoscopy and intubation does not completely prevent the increase in MAP and ICP.3 While the cardiovascular response can be dramatic and substantial, the ICP response may lag behind and persist for a longer period of time.

A neurosurgical patient may present with cerebral hyperemia or an unruptured aneurysm that requires meticulous control of blood pressure during induction and maintenance of anesthesia. Patients also may arrive in cervical collars with limited neck movement or in stereotactic head frames for procedures such as biopsy or tumor resection. The prone position may be required for access to the surgical site and carries its own set of considerations. Lastly, a smooth emergence and recovery are expected and sometimes crucial for the success of the surgery.

Supraglottic Airways

SGAs have played a major role in the management of the anticipated and unanticipated airway.4,5 The original laryngeal mask airway (LMA, Teleflex), invented by Archie Brain, MD, was used for rescue ventilation, and later as a fiber-optic conduit in failed intubation.6 The intubating LMA (LMA Fastrach, Teleflex), also designed by Dr. Brain, allowed for enhanced ventilation and blind endotracheal intubation. The LMA Fastrach was particularly successful in patients with limited cervical spine movement, and could be inserted in various patient positions.7 The second-generation SGAs include the LMA ProSeal (Teleflex), LMA Supreme (Teleflex), LMA Protector (Teleflex), and the i-gel (Intersurgical).

The LMA ProSeal is a laryngeal mask device that features a larger cuff and a drainage tube, allowing access to the gastrointestinal tract. The LMA Supreme is a single-use version with a curved shape for easy insertion. The i-gel is a single-use SGA device that has a gastric access channel but no cuff.

Second-generation SGA devices separate the respiratory and gastrointestinal tract, theoretically reducing the risk for aspiration while providing a more effective seal for positive-pressure ventilation (PPV).8 The LMA Protector is a third-generation device providing gastric access, efficient ventilation, and the potential for endotracheal intubation.9

Strategies for Management

Using an SGA device for a neurosurgical procedure requires knowledge of its function and attention to detail. The second-generation SGA devices are highly recommended because they provide the best conditions for ventilation, and their optimal placement can be confirmed by several performance tests.10 These devices allow one to access and empty the gastric tract as well as maximize the airway seal around the glottis. These design features allow for more effective PPV, which can easily be achieved using volume or pressure-controlled settings. The peak pressure can reach 30 cm of water (H2O), whereas 20 cm H2O is the limit for standard SGA devices.11

It is essential to avoid light anesthesia, which may cause glottic closure and disrupt ventilation. Although muscle relaxants are not necessary for insertion of SGA devices, controlled ventilation is highly recommended for the majority of these procedures, and this may be achieved with administration of muscle relaxants or opioids. Essentially treating the device as an ETT will guide the management of the anesthetic since there are periods of little stimulation, but sometimes abrupt and intense stimulation. Attention to head positioning by the neurosurgeon is crucial, as changes in ventilation may occur with excessive neck flexion. Once the head is fixed in pins or placed on a donut, it is unlikely to move again, and ventilation should be confirmed before proceeding.

Securing the SGA device is obviously important, and while traditional methods of taping are adequate, it helps to anchor the device, preferably against the maxilla, with wide tape. The LMA Supreme features a fixation tab for securing it gently against the upper lip (Figure 1). A modified technique is to use the face mask head straps, which provide a more secure fixation, particularly if the head will be turned or the patient placed in a nonsupine position.12

Craniotomy

Although several case reports describe use of LMA in craniotomy, these were scenarios of failed intubation and the necessity for an airway in fasted patients.13,14 The LMA Fastrach has been discussed extensively as a device for airway management in patients with limited neck movement. It is particularly useful in patients with fixed neck flexion and can be inserted in a variety of positions.

The role of the intubating LMA in a failed intubation scenario was demonstrated by Combes and colleagues.15 In their prospective study of unanticipated difficult intubation, they concluded that the intubating LMA and the gum-elastic bougie effectively solve most problems that occur during unexpected difficult airway management. This was in the era before video laryngoscopy, and the technique has been sadly abandoned by many. It is still useful in certain patients with inadequate mouth opening and compromised ventilation. This is particularly important for neurosurgical patients, who may not easily tolerate repeated laryngoscopy attempts, inadequate ventilation, and excessive hypertension and tachycardia.

Second-generation SGA devices may be useful for brief, urgent procedures such as burr holes in the supine position in fasted patients. Patients may be obtunded and hypertensive due to increased ICP and will likely require small amounts of agent for induction. Ventilation should be controlled after insertion of the device and vital signs carefully monitored during hematoma evaluation and brain decompression. Spontaneous ventilation can be resumed early for assessment and emergence.

Stereotactic Head Frames

Stereotactic localization is widely used in neurosurgery and has revolutionized practice over the past 30 years. The frame may be placed in an awake, sedated patient with local anesthetic injection at the pin sites. Despite moderate access to the airway, head positioning and fixation to the table can make proper positioning for airway management extremely challenging. Procedures are often minimally invasive, such as biopsies or small craniotomies, and the patient may undergo imaging wearing the head frame. General anesthesia is induced in the head frame later, and a plan for airway management must be discussed.

Awake intubation may be required if access is limited and the airway is assessed to be difficult. If awake intubation fails, an alternative technique may be used. The SGA device is extremely useful in this scenario and may be used as the sole airway in appropriate patients who are undergoing the procedure in the supine position. It is important to be familiar with a number of airway techniques and to have a plan for alternative methods of airway management, should these challenges occur.16

Awake Craniotomy

Craniotomy in the awake state is performed with specialized neurosurgical teams in some institutions. Current indications for an awake craniotomy include resection of a lesion in the eloquent or speech center of the brain, mapping for seizure foci, or surgeon preference and expertise.17 Surgical procedures for the treatment of epilepsy, tumors, or arteriovenous malformations (AVMs) are sometimes performed in an awake patient. With refinement of neurophysiologic monitoring techniques, awake craniotomies are necessary in only a small percentage of patients. However, surgery for movement disorders has again increased the use of this technique. Intraoperative complications of awake craniotomy include restlessness and agitation. This may occur when the patient is overly sedated yet experiences discomfort. More serious complications are hypoventilation, nausea, and seizures.18 A change in the level of sedation will often resolve these problems.

It is important to maintain good rapport with the patient, which should be established preoperatively. Positioning of the patient to avoid discomfort, allowing surgical access, and avoidance of a claustrophobic environment are essential and require the cooperation of the entire operating room (OR) staff. The evolution of the anesthetic technique has progressed from fentanyl/droperidol to the current use of propofol infusion with alfentanil, remifentanil, and/or dexmedetomidine.19,20

If necessary, general anesthesia may be required for uncooperative or very young patients. The “asleep-awake-asleep” technique has been utilized in some centers in an effort to minimize patient discomfort and perhaps provide better operating conditions for the surgeon. The patient is given a light general anesthetic with additional local anesthesia and/or a “scalp block,” and is awakened intraoperatively for testing at the appropriate time.21

Airway management can be daunting, and several maneuvers have been reported. Some clinicians also have used nasal airways or continuous positive airway pressure ventilation.22 The most useful technique in recent years has been the use of the SGA device for control of the airway. This has been described in several reports, and can be achieved (with skill) without having to remove drapes or change the position of the patient.23 In our experience, the LMA ProSeal or LMA Supreme is easier to insert so that patients can be induced and reanesthetized for the resection after completion of intraoperative testing. This allows the surgeon a “quiet field” for surgical resection, since many patients become hypercarbic while awake and sedated. The LMA Supreme is particularly advantageous for the ability to provide adequate PPV and deliberate entry into the gastric tract.23

The SGA device also can be used as a conduit for fiber-optic intubation and as a rescue airway technique, as described. Most SGA devices as well as the intubating LMA can be inserted in a variety of patient positions. This is useful in the dreaded situation of accidental extubation in the prone position or loss of the airway in a sedated patient who is fixed in a head frame.24 Assuming the mouth opening is adequate, the device can be easily placed by facing the patient and using the thumb to insert along the hard palate. A case report describes anesthetic induction and management in the prone position for a penetrating spinal injury at the C1-C2 vertebrae using an LMA.25

Prone Position

Elective use in the prone position is considered controversial by some, but can be safely performed in appropriate patients with proper positioning. This technique began with ambulatory and plastics procedures. Patients were induced in the prone position and the device was placed, often successfully. There is a growing body of experience and literature on the utility of this technique with the LMA Supreme. Studies have shown the ease of insertion with the patient in the prone position for surgery. This obviates the need for turning an anesthetized patient and allows for efficient use of OR time.26,27

Sharma and colleagues described use of the LMA Supreme in 205 consecutive patients undergoing elective spine surgery in the prone position.28 First-pass success was achieved in 184 insertions, and there were no failures of either insertion or maintenance of anesthesia. This series was undertaken by a very experienced group and does not represent the typical experience. It serves to demonstrate what can be achieved with planning, skill, and attention to detail. Caveats include careful patient selection, adequate depth of anesthesia before insertion, and a nearby stretcher in case the patient has to be turned supine quickly.

Interventional Neuroradiology

The endovascular treatment of intracranial aneurysm and AVMs is now an option for many patients. This new therapy offers significantly reduced morbidity, mortality, and hospital stay compared with craniotomy. In patients with acute subarachnoid hemorrhage (SAH), considerations must be made for the likelihood of increased ICP, changes in transmural pressure, and cerebral ischemia. During endovascular treatment, the 2 most serious potential complications are cerebral infarction and hemorrhage. Endovascular coiling may be safely applied within hours of the aneurysm rupture with low probability of aneurysm perforation.

General anesthesia is preferred for patients with acute SAH. Despite concern for neurologic evaluation, most neuroradiologists now prefer general anesthesia for optimal imaging of studies and techniques. Airway control through an ETT or LMA allows for improved oxygenation, anesthetic administration, and a motionless patient. Radiological imaging methods include high-resolution fluoroscopy and high-speed digital-subtraction angiography with a “road mapping” function.29 The computer superimposes images onto live fluoroscopy so that the progress of the radiopaque catheter tip can be seen. Any motion during this stage of the procedure profoundly degrades the image. The anesthesiologist is typically off to the side of the patient and must negotiate around the myriad of monitors and equipment, which are part of this terrain. One benefit of this environment is the ability to obtain fluoroscopic confirmation of ETT positioning, confirm proper central line location, if placed, or make the diagnosis of atelectasis.

Although the radiology suite may be in a remote location, the patient with an anticipated difficult airway should be approached in the same manner as in the OR. A potential limiting factor is the flat table, which does not allow the patient’s head to be raised. Supporting blankets should be used to produce the optimal position for ventilation or laryngoscopy, if necessary (Figure 5). Emergence from anesthesia should be smooth, avoiding excessive coughing and “bucking.” Hypertension should be controlled to prevent potential cerebral edema and bleeding at the femoral arterial cannulation site. There is minimal pain, but patients are required to remain supine for awhile—occasionally for 20 minutes of groin compression (Figure 6). The advantages of the SGA device are that the patient can likely begin to breathe without coughing, hypertension, or straining.

ETT/SGA Exchange

Hypertension, coughing, and bucking are preferably avoided in neurosurgical patients. When this is particularly a consideration or the patient has severe asthma or chronic obstructive pulmonary disease, extubation may be facilitated by exchanging the ETT for the LMA (ie, using the LMA as a bridge to extubation).30 This is performed while the patient is still deeply anesthetized, without airway reflexes. After oropharyngeal suctioning, the deflated SGA device is inserted behind the ETT and its cuff inflated. The ETT cuff is then deflated and the tube removed. The patient is gently ventilated until regaining consciousness or remaining at a lighter plane of anesthesia.

It is important to never overinflate an SGA device, as this will cause discomfort upon emergence.31 The exchange technique also is useful when an elaborate head draping is required and excessive neck movement will likely provoke coughing and bucking. The technique also is known as the “Bailey maneuver,” which is used at the Royal National Throat, Nose and Ear Hospital, in London, United Kingdom.31 Perello-Cerda and colleagues, from Spain, performed the technique in a randomized controlled, open-label trial of 42 patients undergoing craniotomy.32 The LMA ProSeal was exchanged for the ETT at the conclusion of surgery. The incidence of cough was higher in the ETT group (87.5%) compared with the LMA ProSeal group (9.5%). In addition, norepinephrine plasma levels rose in both groups and were not significant. Antihypertensive medication was administered to more patients in the ETT group than the SGA group.32

Another strategy is to use an ETT within an SGA device and remove the ETT instead of performing an exchange. This is possible with the i-gel or LMA Protector (Figure 7). A recent Chinese study reported on 60 patients undergoing posterior fossa surgery who were randomly assigned to have standard ETT or “i-gel–facilitated” endotracheal intubation. Mean arterial pressure and heart rate were lower in the i-gel group during intubation and extubation.33 While there are many techniques to facilitate a smooth emergence, it is more challenging in hypertensive patients, smokers, and those with obstructive sleep apnea. The necessity for a postoperative neurologic assessment does not always make prolonged ventilation an option. Having a bridge to extubation also is useful when there is postprocedure scanning or intraoperative radiological assessment before emergence. Having an airway that allows for comfortable ventilation without disruptive movement is beneficial and unique.

Conclusion

SGA devices can be a useful airway alternative for neurosurgical patients, provided there is appropriate patient selection and careful management. The newer second-generation devices are well designed for most situations and can be easily inserted and assessed. Understanding of the positioning, surgical stress, and patient comorbidities is essential for ensuring a safe anesthetic technique. SGA devices provide a number of airway options for neurosurgical patients and should always be readily available.

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