Craniotomy for Asleep 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 right side of the brain and so the patient’s left side will be towards the anesthesiologist.
Preop: No benzodiazepines. Premedicate with benadryl 25 - 50 mg IV and/or fentanyl.
Monitors:Arterial catheter inserted after induction of anesthesia.
Anesthesia: Goals are to provide adequate anesthesia and to maximize the chance of successful mapping and resection of seizure foci: do not administer anesthestic vapors. Induce anesthesia with fentanyl 5-10 µg/kg and propofol plus muscle relaxant of choice, and start a 10 min dexmedetomidine 0.7 ug/kg loading infusion. Verify adequate neuromuscular block prior to intubation to avoid coughing/straining. Tape eyes, insert esophageal temperature probe, and 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 and have the esophageal temperature above 36 C°. Maintain anesthesia with fentanyl infusion 2 – 5 µg/kg/h, dexmedetomidine infusion 0.7 ug/kg/hr (titrate to effect) and up to 70% nitrous oxide. Maintain neuromuscular relaxation throughout unless cortical motor mapping will be done. Use mild hyperventilation only (PaCO2 35 mmHg). Once the bone flap is removed, have the surgeon assess the tightness of the dura and adjust PaCO2 accordingly. Keep propofol in line at all times and give 1 mg/kg in case of seizure. Minor movement may be treated with fentanyl 100 µg push and muscle relaxant, vigorous movement should be treated with propofol 1 mg/kg push. At the conclusion of the initial mapping of seizure foci, the surgeon may request that you give etomidate 7 mg IV in order to bring out any quiescent seizure activity. Make sure to verify that the patient is paralyzed before the etomidate is given. The electrocorticography will be repeated at the end of the resection so it is important to maintain the anesthetic as described until the closure commences. During closure, the fentanyl and dexmedetomidine can be stopped and anesthesia maintained with a propofol/sevoflurane combination. Normalize pCO2 to facilitate spontaneous breathing at the end of the operation. Use of inhalation agents and propofol is usually stopped about 10-15 min before end of surgery, and nitrous oxide at the end of surgery. Consider prophylactic use of labetalol to attenuate emergence hypertension.
Potential complications: Intra- and postoperative seizures. Delayed awakening from anesthetics and/or intracranial pathology. Postoperative intracranial bleeding.
Recovery:Wake patient up and extubate immediately after the operation to allow neurologic examination. Coughing and bucking on the endotracheal tube must be minimized. Use a hemodynamic monitor and supplemental oxygen during patient transport to ICU. Prevent postoperative hypertension to avoid intracranial bleeding.