Awake craniotomy

Awake craniotomy

Anesthesia type	Scalp block MAC GA-awake-GA
Airway	Noninvasive O2 LMA
Lines and access	PIV x2 Arterial line Central line
Monitors	Standard 5-lead ECG Temperature Urine output ABP CVP Neuromonitoring ± Precordial doppler
Primary anesthetic considerations
Preoperative	Comprehensive patient consultation Baseline neuro exam
Intraoperative	Scalp block required Risk of seizure
Postoperative
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An awake craniotomy is a surgical procedure that is sometimes employed for patients undergoing tumor excision or clipping of arteriovenous malformation in regions of the brain that involve speech or motor function. Patients are typically sedated during line placement and cranial opening, and then awakened once the dura is opened. Due to the unconventional nature of the surgery, this technique is generally reserved for patients who have undergone careful preoperative selection, with considerations for temperament, overall health status, and adequate education.

The procedure can be performed using either monitored anesthesia care (MAC) or using an asleep-awake-asleep (SAS) technique. A recent meta-analysis suggests that MAC was associated with lower likelihood of failure and shorter procedure time, while SAS was associated with lower incidence of intraoperative seizure. The use of non-pharmacological anxiolytic techniques (e.g. hypnosis) to achieve success with an awake-awake-awake technique has also been reported.

Preoperative management

Patient consultation

Detailed consultation to psychologically prepare the patient is essential to set expectations and address questions to minimize anxiety intraoperatively.

• Perform prior to the day of surgery
• Should include the neuropsychology team that will be performing intraoperative testing
• Discuss non-medical modalities of intraoperative anxiety management (as feasible)
  • Music, hypnosis, phone calls, etc.

The patient experience of the surgical procedure should also be discussed in detail:

• Lines and foley catheter will be placed under sedation
  • May experience the feeling of a full bladder when awakened
• Patient's head will be unable to move
  • Will likely feel pressure
  • Pain is possible, but can be addressed
  • May experience dry mouth
• Patient will be able to communicate with the OR staff at all times while awake
• Patient should be encouraged to communicate any and all concerns during the operation
  • discomfort with position should be addressed early before pt becomes distressed
  • presence of aura, indicating impending seizure
• Patient will be asked to perform tasks and/or answer questions to ensure neurologic intactness throughout the procedure

Patient evaluation

System	Considerations
Neurologic	Neuro exam to establish baseline function and deficits. Consider signs and symptoms of: Increased ICP Impingement of motor areas Intracranial bleeding.
Cardiovascular	Evaluate for comorbidities which may be exacerbated by intraoperative stress during the procedure (i.e. being under drapes, head clamped in Mayfield pins, surgical sounds, etc.). Increased ICP may result in Cushing's triad of HTN, bradycardia, and irregular respiratory pattern.
Pulmonary	Significant comorbidities (e.g. advanced COPD requiring supplemental oxygen or history of exacerbation, asthma with history of exacerbations requiring rescue inhaler use, etc.) should be assessed in advance to determine suitability for this procedure. Detailed airway exam to estimate risk of airway compromise during sedation. OSA, morbid obesity, abnormal upper airway anatomy are relative contraindications to awake technique.
Gastrointestinal	Due to the lack of a protected airway and risk of aspiration, relative contraindications to this procedure include: History of nausea or vomiting (especially if present on the day of surgery) History of uncontrolled GERD If in Mayfield pins, active GERD may trigger coughing, resulting in potential for injury to head and neck
Endocrine	In patients with a history of diabetes, intraoperative glucose should be closely monitored. Hypoglycemia and extreme hyperglycemia may result in altered mental status that could interfere with neurological monitoring, disinhibition, and airway compromise.

Labs and studies

• Complete blood count
• Metabolic panel
• Coagulation panel
• Type and screen

Operating room setup

• Be aware of type of table and head support to be employed to adjust anesthesia technique accordingly

Patient preparation and premedication

• For patients who are used to a morning cup of coffee, consider caffeine 200 mg PO before surgery to reduce the risk of withdrawal headache
• Glycopyrrolate may be useful as an antisialagogue

Regional and neuraxial techniques

Video demonstration of a scalp block

Scalp blocks are essential to achieve adequate analgesia during the awake phase.

• Typically placed during the pre-awake phase using bupivacaine 0.5% or ropivacaine 0.5% (with epinephrine)
  • If faster onset is desired, can be pre-blocked with buffered lidocaine 2%
  • Placement prior to pinning and exposure will reduce anesthetic requirements
• A single syringe with a combination of lidocaine, bupivacaine, sodium bicarbonate, and epinephrine can provide fast onset, long duration, and reduced discomfort during injection. For example, in a 10 mL syringe, a recommended mixture would be:
  • 4.5 mL of 2% lidocaine with 1:100,000 epinephrine
  • 4.5 mL of 0.5% bupivacaine with 1:200,000 epinephrine
  • 0.4 mL of 8.4% sodium bicarbonate
• Can be supplemented during the awake phase using buffered lidocaine 2%

Intraoperative management

Monitoring and access

• Arterial line
• CVC vs PICC
• Large bore IV(s)
• Microphone for patient to communicate
• ± Precordial doppler

Induction and airway management

The pre-awake phase of the procedure involves line placement, positioning, and cranial opening. This phase may be achieved using MAC or general anesthesia with similar outcomes, and largely depends on institution and practitioner preference. The decision on what technique will be informed by experience with the surgical team, a common determining factor is the duration of the pre-awake phase.

If using MAC:

• Provide sedation using:
  • Midazolam 1-10 mg IV (titrated incremental doses)
  • Dexmedetomidine 0.2-0.7 mcg/kg/hr (±1 mcg/kg bolus)
  • Propofol 25-50 mcg/kg/min
• Place lines with field blocks using buffered lidocaine for patient comfort

If using general anesthesia:

• Induce with propofol
• LMA use is typical, but use ETT if indicated
• Remifentanil is the preferred narcotic due to rapid titratability

Positioning

Positioning will vary depending on the surgical approach. Patients can be positioned supine, semi-laterally, or laterally.

The patient's head is typically secured in a pinned frame.

• Pin sites should be infiltrated with local anesthetic

Maintenance and surgical considerations

Intraoperative seizures

• Seizures may occur during intraoperative stimulation mapping. Rates of incidence vary widely, ranging between 3-16%.
• Intraoperative seizures must be rapidly recognized and treated using:
  • Cold water irrigation of the surgical field
  • Low doses of propofol (30-50 mg)
• Untreated intraoperative seizures may precipitate catastrophic complications
  • Postictal delirium can preclude effective neuropsychological monitoring and necessitate abortion of the procedure.
  • Generalized seizures may induce breath holding, and valsalva. Increased intrathoracic pressure suddenly decreases venous drainage from the brain and transcranial herniation can occur rapidly.
• There is limited evidence to support the use of levetiracetam for seizure prophylaxis.

Post-resection management

Patients can typically be re-sedated after resection has been completed, though some surgeons prefer to keep patients awake to continue conscious neurological monitoring.

Emergence

• If non-instrumented airway, sedation can be discontinued during closure and patient allowed to emerge after removal from pinned frame
• If LMA/ETT in place, ensure intact airway reflexes and smooth removal

Postoperative management

Disposition

• Typically ICU for frequent neuro exams

Pain management

• Scalp block will provide analgesia for 12-16 hours
• If supplemental analgesia is required
  • Acetaminophen
  • Use narcotics with caution as can interfere with neurologic examination

Procedure variants

	Variant 1	Variant 2
Unique considerations
Position
Surgical time
EBL
Postoperative disposition
Pain management
Potential complications