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Awake Craniotomy: A New Airway Approach

Sivasankar, Chitra MD; Schlichter, Rolf A. MD; Baranov, Dimitry MD; Kofke, W. Andrew MD, MBA, FCCM

doi: 10.1213/ANE.0000000000001072
Neuroscience in Anesthesiology and Perioperative Medicine: Brief Report
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Awake craniotomies have been performed regularly at the University of Pennsylvania since 2004. Varying approaches to airway management are described for this procedure, including intubation with an endotracheal tube and use of a laryngeal mask airway, simple facemask, or nasal cannula. In this case series, we describe the successful use (i.e., no need for endotracheal intubation related to inadequate gas exchange) of bilateral nasopharyngeal airways in 90 patients undergoing awake craniotomies. The use of nasopharyngeal airways can ease the transition between the asleep and awake phases of the craniotomy without the need to stimulate the airway. Our purpose was to describe our experience and report adverse events related to this technique.

Published ahead of print November 17, 2015

From the Department of Anesthesiology, University of Pennsylvania, Philadelphia, Pennsylvania.

Accepted for publication September 30, 2015.

Published ahead of print November 17, 2015

Funding: None.

The authors declare no conflicts of interest.

Reprints will not be available from the authors.

Address correspondence to Chitra Sivasankar, MD, University of Pennsylvania, 3400 Spruce St., 7 Dulles, Philadelphia, PA 19014. Address e-mail to schitra12@hotmail.com.

The anesthetic management for an awake craniotomy involves a collection of different anesthetic techniques and practices. There are 3 phases of an awake craniotomy: before, during, and after the intraoperative cognitive testing. These techniques are described as asleep-awake-asleep, asleep-awake-awake, or awake-awake-awake.1–4 Most articles cite the asleep-awake-asleep technique during which an endotracheal tube or a laryngeal mask airway is used for airway management during the asleep portions.4 The goal of this retrospective analysis was to describe and assess a different approach, routinely used at the University of Pennsylvania, using bilateral nasopharyngeal airways as an alternative to an endotracheal tube or a laryngeal mask airway.

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METHODS

After obtaining IRB approval, we examined anesthesia records, operative notes, postoperative notes, and discharge summaries of all patients who had undergone this awake craniotomy neurosurgery at the Hospital of the University of Pennsylvania from 2006 to 2014. On the basis of our knowledge of our incidence of awake craniotomies, we obtained IRB consent to review charts from August 2004 to August 2014, but we were not able to abstract all the relevant information for patients from 2004 to 2006. Written consent was obtained from patients for publication of their photographs.

The anesthetic technique used for each patient was asleep-awake-asleep, with bilateral nasopharyngeal airways connected via a double-lumen tube adapter to the anesthesia machine circuit (Fig. 1). IV anesthetics were used with doses adjusted as needed to initially produce an unresponsive spontaneously breathing hypnotic state, followed by a responsive state, and then resumption of a hypnotic state after resection of the lesion.

Figure 1

Figure 1

These adverse events were recorded:

Cardiac:

  • Hypertension: systolic blood pressures >150 mm Hg
  • Hypotension: systolic blood pressures <90 mm Hg
  • Bradycardia: heart rates <50 bpm
  • Tachycardia: heart rates >90 bpm

Respiratory:

  • Hypoxemia: SpO2 <90%;
  • Hypercarbia: PaCO2 >45 mm Hg
  • Aspiration and/or vomiting: documented in postoperative notes

Neurologic:

  • Intraoperative brain edema: described in operative or anesthetic records
  • Nausea
  • Uncooperative patient
  • Oversedation/inability to properly awaken for cognitive testing
  • Epistaxis from the placement of the nasopharyngeal airway
  • Conversion to general anesthesia (GA): defined by the insertion of a laryngeal mask airway or endotracheal tube to control ventilation
Figure 2

Figure 2

Three stages during Awake Craniotomy: General Protocol.

  1. Based on the patient’s baseline neurologic examination, the patient can be given IV midazolam up to 2 mg, fentanyl 50 to 100 μg, and dexmedetomidine bolus. An arterial cannula is placed under local anesthesia. Topical phenylephrine and lidocaine are applied for vasoconstriction and local anesthesia of the nasopharyngeal mucosa. Bilateral nasopharyngeal airways are placed and then connected via a double-lumen endotracheal tube connector to the anesthesia circuit. High-flow oxygen between 8 and 10 L/min is given. The CO2 sampling port on a double-lumen connector or anesthesia circuit is used to measure end-tidal carbon dioxide and confirm ventilation (Fig. 2). A pulse oximeter, electrocardiogram, intraarterial blood pressure monitor, end-tidal capnography, respiratory rate monitor, and axillary temperature probe are used. Sedation is provided with propofol (30–90 μg/kg/min), dexmedetomidine (bolus at 1 μg/kg over 10 minutes and infusion 0.4–0.8 μg/kg/h), and remifentanil (0.01–0.03 μg/kg/min). A Foley catheter is inserted, facilitated with lidocaine gel. Bilateral scalp nerves are blocked with either 0.5% bupivacaine or 0.5% ropivacaine.3 Sedation is deepened before pinning and incision while maintaining unobstructed spontaneous ventilation.
  2. When the dura is exposed, all sedation is stopped and the patient is allowed to wake up spontaneously. Speech/motor mapping is then performed. Once the patient is awake and communicating well, remifentanil and dexmedetomidine can be restarted to maintain a level of consciousness appropriate for continued cognitive testing.
  3. After resection is completed, the level of sedation is deepened with propofol, dexmedetomidine, and remifentanil at a level that preserves spontaneous ventilation. At the end of the procedure, sedation is stopped, and the patient is transported to the neurointensive care unit.
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RESULTS

Records of all 90 patients who underwent this technique from 2006 to November 2014 were identified. ASA physical status and other demographics are listed in Table 1.

Table 1

Table 1

Table 2

Table 2

Adverse events are summarized in Table 2. There were no instances of intraoperative vomiting or epistaxis. There were no conversions to GA related to hypoxemia or hypercarbia. Hypoxemia occurred in 2.2% of the patients, but in each instance it was reversed. Thirty patients had 2 or more adverse events, such as hypertension, hypercarbia, and/or brain swelling, and this is further detailed in Table 2.

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DISCUSSION

Most authors describe the asleep-awake-asleep technique for awake craniotomies.5–7 A variety of approaches to airway management has been described. These include the use of nasal cannula,5 simple facemask,7 laryngeal mask airway, or endotracheal tube. Skucas and Artru5 reported the successful use of nasal cannula/facemask for epilepsy surgery in >300 patients. The primary problems with the use of nasal cannula are difficulty in reliably measuring end-tidal carbon dioxide and also keeping the airway patent in sedated patients with problems such as obesity or obstructive sleep apnea. When using flammable skin preparations, oxygen pooling under the drapes with an open oxygen source can support combustion in the operating room.8 Finally, prevention of coughing and laryngospasm when using an endotracheal tube or a laryngeal mask airway requires a deeper plane of anesthesia.9

This case series reports generally successful use of bilateral nasopharyngeal airways with double-lumen connectors attached to an anesthesia circuit in awake craniotomy patients. This technique was chosen because it has several advantages: (1) It allows for a smooth transition between the asleep and awake phases of the surgery without the need to manipulate the airway; (2) The development of upper airway obstruction with snoring and associated vibration of the surgical field is minimized, partially via the ability to add continuous positive airway pressure via the anesthesia circuit; (3) End-tidal CO2 readings are easily obtained; and (4) Spontaneous ventilation can be additionally monitored by spirometry. Occasionally, as may be needed with oversedation or hypercarbia, ventilation can be manually supported and sometimes facilitated by manually closing the mouth.

Hemodynamic changes such as hypertension and tachycardia are fairly common in awake craniotomies. In our case series, hypertension was seen in 53% of patients.5,10,11 It was not sustained and was managed with analgesics (remifentanil) and antihypertensives (nicardipine and labetalol). Hypertension has been reported in 12% to 64% of patients undergoing craniotomy under GA, suggesting that the 2 approaches can entail similar hemodynamic consequences.12

Hypoxemia10 and hypercarbia can make for suboptimal neurosurgical conditions. Our incidence of hypoxemia was 2.2% and hypercarbia was 18%. These problems were managed by the reduction of anesthetic doses and by the ability to provide positive pressure and support ventilation via the anesthesia circuit attached to the nasopharyngeal airways. Similar to another report,5 no adverse sequelae of these abnormalities in gas exchange were noted.

On the basis of their lack of occurrence (zero numerator), our observations indicate a probability of <3% chance of inability to support gas exchange, need to convert to GA, epistaxis, or vomiting from this technique.13 Although a direct comparison with other approaches was not done, we suggest that this approach is an acceptable alternative to airway maintenance in an awake craniotomy.

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DISCLOSURES

Name: Chitra Sivasankar, MD.

Contribution: This author helped analyze the data and write the manuscript.

Attestation: Chitra Sivasankar has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the archival author.

Name: Rolf A. Schlichter, MD.

Contribution: This author helped design the study and conduct the study.

Attestation: Rolf A. Schlichter has seen the original study data and approved the final manuscript.

Name: Dimitry Baranov, MD.

Contribution: This author helped design the study and conduct the study.

Attestation: Dimitry Baranov approved the final manuscript.

Name: W. Andrew Kofke, MD, MBA, FCCM.

Contribution: This author helped analyze the data and write the manuscript.

Attestation: W. Andrew Kofke has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the author responsible for archiving the study files.

This manuscript was handled by: Gregory Crosby, MD.

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