The remote location of a NORA procedure suite presents the anesthesiologist with specific challenges, including:
- The need to transport and set up anesthesia equipment in an unfamiliar environment
- Lack of trained help in a medical emergency or with the need for critical resuscitation, including massive transfusion protocols
- Lack of a full understanding of technical considerations and anesthetic implications for the proposed procedure by the anesthesiology team
- Need for effective communication between the procedural and the anesthesia teams
- Potential for increased radiation risk if appropriate safety procedures are not followed
- Unfamiliar protocols in an unfamiliar environment.
Nevertheless, ASA standards and practice parameters for NORA should be adhered to in every clinical encounter in this practice setting (asamonitor.pub/3mRrUOX). Three rapidly growing IR procedures are briefly discussed below that can markedly improve patient outcomes; they do, however, require special anesthetic considerations.
Transbronchial cryobiopsy in parenchymal lung disease
Transbronchial cryotherapy was first used as a palliative treatment in bronchial obstruction in 1996. Over the years, however, increasing safety and effectiveness of transbronchial procedures have expanded to include cryobiopsy. In a cryobiopsy, compressed gas, usually nitrous oxide, is used at a high flow rate through the cryoprobe to cool the tip to -79 to -89°C for three to five seconds to obtain a freeze-thaw tissue biopsy sample (Respiration 2009;78:203-8).
Transbronchial cryobiopsy (TBCB) is performed under fluoroscopic guidance. In TBCB, a cryoprobe is introduced through the side channel of the bronchoscope. Following the completion of the freeze-thaw cycle, the bronchoscope is removed with the frozen tissue sample attached to the tip of the cryoprobe. The cryoprobe tip with the frozen biopsy is then submerged in saline to thaw and release the tissue sample. The cryoprobe is removed from the working bronchoscopy channel, and the bronchoscope is reinserted to assess for bleeding. This technique permits larger biopsy sampling at a more peripheral and deeper level of lung parenchyma for the diagnosis of interstitial lung diseases, neoplastic diseases, and infectious processes as well as ill-defined inflammatory masses/lesions in the deep lung periphery not usually accessible with traditional bronchoscopy biopsy (TBB) (PLoS One 2014;9:e86716). Cryobiopsy, however, disrupts a much greater volume of lung parenchyma than does a traditional forceps lung biopsy performed through the bronchoscope. Therefore, pneumothorax (12%) and moderate to severe bleeding (39%) are more common and severe, especially if the cryoprobe is malpositioned and the pleural line is breached. Published studies report a 78% diagnostic yield in obtaining an accurate diagnosis with cryobiopsy compared to 34% in TBB, thus reducing the need for an open lung biopsy (OLB). Two recent meta-analysis evaluated the diagnostic yield and safety of cryobiopsy compared to open lung biopsy. While the diagnostic yield for open lung biopsy was as high as 98.7% compared with 83.7% in cryobiopsy, adverse events such as persistent fevers, prolonged air leak, and acute exacerbation of interstitial lung disease were higher in the open lung biopsy group. In addition, hospital length of stay was decreased in the cryobiopsy group (2.6 days vs. 6.1 days in the OLB group) and was associated with a lower 30-60-day mortality (0.7% vs. 1.8% in the OLB group). This procedure can be successfully performed on an outpatient basis, thus reducing hospitalization (Ann Am Thorac Soc 2016;13:1828-38).
Apart from the general considerations of NORA, the principles of anesthetic management for TBCB are related to the location of the lesion and the patient’s medical condition. Preparedness for the potential need for a difficult airway algorithm, difficult intraprocedural ventilation pathway, lung isolation techniques, blood transfusion strategies, and critical resuscitation protocols in the event of pulmonary hemorrhage should be part of the anesthetic plan. TBCB has been performed successfully under monitored anesthesia or under general anesthesia with a laryngeal mask airway. However, use of a large endotracheal tube or rigid bronchoscope is most appropriate for bleeding readiness as they provide a large channel through which a flexible bronchoscope or bronchial blocker can be placed proximally to the biopsy site to occlude bleeding. Measures to improve patient safety continue to evolve, especially regarding the risk of pneumothorax and hemorrhage (Can J Anaesth 2018;65:822-36). This is a relatively new procedure and as a result there is substantial procedural variation among centers. Several multicenter trials are currently under way to address the efficacy, standardization, and safety of cryobiopsy, which is rapidly gaining momentum to replace OLB as the first modality in the diagnosis of parenchymal lung disease.
Atrial fibrillation (AF) ablation using a patented temperature probe without need for fluoroscopy
The complex AF ablation is performed in the interventional/electrophysiology suite with anesthesiology support. AF ablation is usually associated with prolonged fluoroscopy exposure compared to other types of electrophysiology procedures, exposing staff and patients to higher risk of radiation-associated side effects (J Am Heart Assoc 2018;7:e008233). Thus, performing cardiac ablation therapy for AF using a temperature probe without the need for fluoroscopy may lead to a significant decrease in radiation exposure. The use of an electroanatomic mapping system incorporating 3D modality and transesophageal echocardiography (TEE) have led to a near-zero fluoroscopy approach to AF ablation therapy. The largest series to date with near-zero fluoroscopy technique in 481 patients compared the traditional approach to a zero-fluoroscopy approach. The procedure time was equivalent in both groups. There was no significant difference in patient safety, complications, or clinical outcomes between the two groups, rendering the near-zero fluoroscopy AF ablation technique feasible, safe, and equally effective (Pacing Clin Electrophysiol 2018;41:611-9). Furthermore, simple changes in procedural habits such as removing the lead apron after atrial transseptal puncture and solely relying on electroanatomic mapping for this point has dramatically decreased fluoroscopy time from an average of 23 minutes to between 2.7 to 4.2 minutes (Europace 2015;17:1694-9).
The decision on the selection of an appropriate anesthesia technique, including monitored anesthesia care or general anesthesia (GA), adjuvant agents, the use of invasive monitoring in addition to standard monitoring, and /or TEE should involve a team approach with the cardiology team taking individual patient needs and medical condition into account (A A Case Rep 2014;3:116-7). Multiple factors affect the selection of anesthesia for patients undergoing AF ablation therapy. Many patients have severe cardiac or pulmonary disease and are at a high risk for hemodynamic instability or acute pulmonary decompensation. Furthermore, the inability of the patient to tolerate prolonged periods without movement required for ablative procedures may require GA. The electrophysiologist may require high-frequency jet ventilation (HFJV), as certain critical periods during ablative therapy require a decrease in chest wall excursion. ETCO2 monitoring and frequent arterial blood gas monitoring for hypercarbia are required if HFJV is used. Benefits versus risks of HFJV should be considered in patients with pulmonary disease and in the obese, as HFJV can increase the risk of barotrauma due to hypercarbia and increase plateau pressure (Acta Anaesthesiol Scand 2017;61:1066-74). Anticoagulation with heparin is commonly administered during AF ablative therapy, and monitoring of activated whole blood clotting time is utilzed to achieve adequate heparin effect and protamine reversal at the end of the procedure. Postoperatively, patients should remain supine for a few hours after removal of the large femoral arterial sheath (J Cardiothorac Vasc Anesth 2018;32:1892-1910).
Transarterial chemo-embolization therapy (TACE)
The trend toward minimally invasive procedures and novel technologies in IR has given patients more options for non-surgical treatment of cancer conditions. A more complicated treatment involves combining a high dose of chemotherapy and TACE. TACE has been the gold standard for treating hepatocellular carcinoma and is considered in metastatic lesions and other cancer forms when standard therapies or surgical resection are not an option (ISRN Gastroenterol 2012;2012:480650). TACE may also be combined with local ablation therapy or radiation therapy. Although there are no absolute contraindications to TACE, patient selection is essential to minimize adverse events and have a desired clinical outcome. Relative contraindications include abnormal liver function tests, severe comorbidities, and risk of bleeding from prior transjugular intrahepatic portosystemic shunt or untreated esophageal varices that pose a high risk of bleeding (J Hepatol 2014;61:1287-96). Post-procedure ischemic changes to the liver may manifest as post-embolization syndrome in up to 80% of patients. Clinical findings include fever, nausea, upper right quadrant pain, ileus, and increased liver function tests that may last three to four days. Periprocedural care includes hydration and maintenance of normovolemia, antiemetic, antihistamine, and steroid administration. Antibiotics are not routinely administered. However, in the setting of a biliary obstruction or intraprocedural manipulation, antibiotics should be considered to decrease the risk of infection (AJR Am J Roentgenol 2011;197:W343-5). Patients with a history of carcinoid cancer scheduled for TACE procedures should have octreotide administered preoperatively to minimize acute hormone release from tumor necrosis and avert a carcinoid crisis (Cancer J 2003;9:261-7). Bevacizumab, a monoclonal antibody used in the treatment of various cancers, should be discontinued four to six weeks before TACE therapy as it is associated with increased incidence of sepsis and periprocedural vascular events.
The anesthesiologist should be aware that a lidocaine infusion may be given intermittently during TACE between chemotherapy doses to decrease postoperative pain (J Vasc Interv Radiol 2009;20:203-8). ASA standards and practice parameters for NORA apply in the care of patients for TACE (asamonitor.pub/3s4a9wu). Postoperatively, patients are admitted for overnight observation or, if criteria are met, discharged to home.