Craniotomy for excision of tumor with SSEPs

General: Patients may be symptomatic or asymptomatic. Symptoms may be due to location of tumor or due to increased ICP. You should know the location, kind (if known) and size of the tumor(s), any preop neurological deficits and symptoms and if the patient is at risk for increased ICP. Patients are often taking dilantin, tegretol or keppra and/or steroids.
Preop: Start an IV. Premedicate with up to 2 mg of midazolam depending on patient’s mental status. None if altered mental status (prevent further increase in ICP)
Monitors: Routine monitors. Arterial and Foley catheters inserted after induction of anesthesia.
Anesthesia: Goals are to decrease ICP (if high), to maintain adequate CPP (at least 70 mmHg) to prevent cerebral ischemia from brain retraction, and to allow intraoperative SSEP monitoring. Patients typically receive 1-2 g of Cefazolin, and 4-10 mg of decadron before skin incision, and if indicated up to 1 g/kg of mannitol on skin incision (verify all with surgeon). Induction with propofol. In case of increased ICP, have patient hyperventilate during preoxygenation and continue hyperventilation with mask as soon as possible after induction of anesthesia. Fentanyl 5 μg/kg in divided doses throughout induction, prior to intubation. Verify adequate neuromuscular blockade prior to intubation to avoid coughing/straining. Maintain neuromuscular relaxation (vecuronium or rocuronium). Remember the increased dose requirements for muscle relaxants in patients taking tegretol or dilantin. Tape eyes, insert esophageal temperature probe, and at least one additional large bore IV. Patient position will depend on location of tumor. Maintain anesthesia with oxygen, propofol infusion, and a fentanyl infusion 2 μg/kg/hr. Obtaining good baseline SSEPs is important. Avoid nitrous oxide and minimize halogenated anesthestics, as both have a negative effect on SSEPs. Maintain euvolemia (Lactated Ringer’s). Use mild hyperventilation (PaCO2 35 mmHg). Once the bone flap is removed, have the surgeon assess the tightness of the dura. Decrease ICP further if necessary (pCO2, mannitol, propofol, head up etc.). If the SSEPs diminish during the procedure this may be an indication of cerebral hypoperfusion and it may be appropriate to increase the MAP by 10- 20% (communicate with surgeons and neurophysiologists). Fentanyl infusion is usually stopped at the beginning of closure. Normalize pCO2 to facilitate spontaneous breathing at the end of the operation. Use of propofol is usually stopped about 10-15 min before end of surgery. Reverse residual neuromuscular blockade once the Mayfield pins have been removed. Consider prophylactic use of labetalol to attenuate emergence hypertension
Potential complications: 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.

Last revised 05/2013 Talke