Intracranial AVM Surgery

General: Patients may be symptomatic or asymptomatic, may have a ruptured or unruptured AVM(s), may be intubated, and may have vasospasm (not very common). You should know the location of the AVM(s) and possible coexisting aneurysm(s). Most patients will have anesthesia for preoperative embolization of the AVM.
Preop: Premedicate with up to 2 mg iv midazolam depending on patients mental status. 
Monitors: Routine monitors. Arterial catheter inserted prior to intubation. Foley catheter
after induction of anesthesia. Frequently also SSEP monitoring.
Anesthesia: Goals are to reduce the volume of intracranial contents (ICP) and to maintain adequate CPP (at least 70 mmHg) to prevent cerebral ischemia from brain retraction, brain swelling and vasospasm. Perioperative AVM rupture from hypertension is possible, but rare. However, in case of a coexisting aneurysm, hypertension must be avoided. Patients typically receive 1-2 g of Cefazolin, 10 mg of decadron and 1 gm/kg of mannitol on skin incision (verify all with surgeon). Induction of anesthesia with propofol. Avoid hypo- and hypertension. Fentanyl 5 µg/kg in divided doses throughout induction, prior to intubation. Tape eyes, insert esophageal temperature probe, and at least one additional large bore IV. Patient position will depend on location of AVM. Maintain anesthesia with propofol infision (around 100 ug/kg/min), low dose inhalation agent (less than 0.5 MAC), a fentanyl infusion 2 µg /kg/hr. Maintain muscle relaxation throughout the procedure. Remember the increased dose requirements for muscle relaxants in patients taking tegretol or dilantin. Use moderate hyperventilation (PaCO2 30 mmHg). Maintain euvolemia (mainly Lactated Ringer’s solution). Check that blood is available in the OR. For EEG burst suppression increase propofol infusion to 150 ug/kg/min and administer additional propofol boluses (50 mg) till burst suppression is achieved. Administer additional propofol boluses as needed to maintain burst suppression (communicate with neurophysiologists). As high dose propofol may delay awakening, reduce/eliminate the use of other anesthetics. If use of high dose propofol decreases MAP, you may need to start a phenylephrine infusion to maintain adequate CPP. Fentanyl infusion is usually stopped at the beginning of closure (or burst suppression if used). Use of inhalation agents and propofol is usually stopped about 10-15 min before end of surgery. Consider reducing all anesthetic drug doses in patients with altered mental status. Discuss postoperative blood pressure control with the surgeon before waking up the patient. Typically postoperative hypertension is avoided to minimize bleeding from a coexisting aneurysm or residual AVM, as well as to avoid postoperative hyperemia. Consider prophylactic use of labetalol to attenuate emergence hypertension.
Potential complications: Perioperative bleeding from AVM, cerebral ischemia from brain swelling, retractor pressure, inadequate CPP (increased ICP, vasospasm), postoperative intracranial hemorrhage, postoperative brain swelling (normal pressure breakthrough hyperperfusion).
Recovery: Wake patient up, and extubate if possible, immediately after the operation to allow neurologic examination. Maintain blood pressure at or below baseline values (discuss with surgeon). Use a hemodynamic monitor and supplemental oxygen during patient transport to ICU.

Last revised 05/2013 Talke