Awake craniotomy is a surgical technique 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. 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.
As with all neurosurgical techniques, a careful preoperative neurological history and exam should be conducted and documented preoperatively to obtain a baseline assessment of function preoperatively. This exam should be particularly focused on eliciting deficits that may exist due to the nature of the lesion that is to be intervened on.
Patients may exhibit signs and symptoms of increased ICP, neurological deficits from impingement of motor areas, or intracranial bleeding.[1]
Cardiovascular
Assess for cardiovascular comorbidities prior to the day of surgery
Acute intraoperative stress response associated with the procedure (i.e. being under drapes, head clamped in Mayfield pins, listening to the sound of the surgeons working, etc.) may in some instances result in cardiovascular dysfunction.
Increased ICP may result in "Cushing triad" of HTN, bradycardia, and irregular respiratory pattern.[2]
The patient should have demonstrated no significant issues managing situations requiring exertion and psychological responses (e.g. panic episodes) that might result in tachyarrhythmias.
Respiratory
Any significant respiratory comorbidity (e.g. advanced COPD requiring supplemental oxygen or history of exacerbation, asthma with history of exacerbations requiring rescue inhaler use, etc.) should elicit a preoperative assessment with an physician preoperatively prior to the day of surgery for determination of suitability for this procedure.
Gastrointestinal
History of nausea and/or vomiting, especially on the day of surgery, should result in a careful reassessment in terms of proceeding to surgery immediately due to risk of intraoperative aspiration.
History of significant uncontrolled gastrointestinal reflux (GERD), may be a contraindication for this procedure due to periods of the procedure that require the lack of protected airway. If patient is in Mayfield pins, active GERD may trigger cough, resulting in potential for injury to head and neck.
Hematologic
Any issues with normal coagulation should be assessed to determine if significant blood loss will result, and anesthetic technique adjusted accordingly, including invasive monitoring, preoperative type and screen, and adequate IV access.
Renal
The patient should be informed that a Foley catheter will be placed at the beginning of the procedure under sedation, and that they will have the sensation of the catheter in their lower urinary tract when awakened during the procedure.
Endocrine
In patients with a history of diabetes mellitus, intraoperative glucose monitoring should be routinely conducted to prevent complications. For an awake technique in particular, hypoglycemia and extreme hyperglycemia may result in altered mental status that could result in issues with inappropriate neurological monitoring during tumor excision, disinhibition, and airway compromise.
Patients with a history of other endocrine disorders should also be counseled on possible complications associated with their particular disease process as it relates to anesthesia.
Labs and studies
Verify normal coagulation studies
Obtain CBC, and electrolyte panel prior to surgery
Operating room setup
Be aware of type of table and head support to be employed to adjust anesthesia technique accordingly.
Patient preparation and premedication
The patient should counseled extensively on the process of awake craniotomy in great detail to avoid surprises that may result in untoward anxiety intraoperatively.
premedication with a short-acting benzodiazepines such as midazolam (in an incremental titrated dose administration to 1-10 mg IV)[2]
dexmedetomidine (0.2-0.7 mcg/kg/hr) may be helpful for preoperative line placement[2]