Craniotomy for awake seizure surgery

General: All patients have medically refractory and long-standing seizure disorder. Their normal anticonvulsant doses will have been decreased in order to ensure that the seizure foci are active. Do not administer medications that can diminish the activity in the seizure foci. The lesion will almost certainly be on the left side of the brain and so the patient’s right side will be towards the anesthesiologist.

Preop: No benzodiazepines. Start an IV and tape IV(s) well. Premedicate with benadryl 25 - 50 mg IV and/or 50-100 μg fentanyl.

Monitors: Routine monitors. Arterial and Foley catheters inserted after beginning of sedation. Axillary temperature measurement.

Anesthesia: Goals are to provide adequate sedation and to maximize the chance of successful mapping and resection of seizure foci. After arrival to operating room, apply monitors, and nasal cannula O2 taped to cheeks. Place at least one additional large bore IV. Mayfield head pins are usually not used. Patients typically receive 1-2 g of Cefazolin, and 10 mg of decadron before skin incision. Mannitol is not usually used for these cases. Keep the room warm and patient covered to keep the patient thermally comfortable. Sedation is typically achieved with remifentanil (0.05 μg/kg/min and higher), dexmedetomidine and communication/rapport (a lot) with the patient. NEVER have the patient over sedated (respiratory depression/apnea).

Maintain sedation with remifentanil and dexmedetomidine infusions. Start dexmedetomidine with 0.7 ug/kg loading dose over 10 min followed by a 0.7 ug/kg/hr infusion. Titrate dexmedetomidine to appropriate level of sedation and remifentanyl to RR of 8-12. Patients taking anticonvulsants appear to require higher than usual dexmedetomidine doses. Keep propofol in line at all times and give 1 mg/kg in case of seizure. Analgesia will be provided by local anesthesia (by surgeons). May need to use the anesthesia machine circuit to blow oxygen/air toward patients face to prevent rebreathing of CO2. Remind the patient of the loud noise before drilling of bone.

Create a clear tunnel for patient perform speech mapping and view slides by using combination of blue clips and tourniquets to hold up towels and drapes. When requested, position small microphone close to patient’s mouth. Approximately 30 min and 5 min before mapping, stop dexmedetomidine and remifentanil infusions, respectively. Restart the infusions once mapping has been completed.

The electrocorticography will be repeated at the end of the resection so it is important to maintain sedation as described until the closure commences. During closure, additional amnesia and sedation may be provided, if necessary, with midazolam 2 mg in divided doses, and a propofol infusion.

Potential complications:  Intra- and postoperative seizures. Apnea, respiratory depression, high pCO2, agitation, N/V. Postoperative intracranial bleeding.

Recovery: Discontinue sedative infusions. Use a hemodynamic monitor and supplemental oxygen during patient transport to ICU. Prevent postoperative hypertension to avoid intracranial bleeding.