Computerized Electroencephalographic Monitoring and Selective Shunting

Publisher Website
Google Scholar
Abstract
During carotid endarterectomy (CEA), phenylephrine infusions are commonly used to induce hypertension during carotid clamping in an attempt to increase collateral cerebral blood flow and prevent cerebral ischemia. Although this practice appears to increase the incidence of intraoperative myocardial ischemia during CEA when general anesthesia is employed, whether the limited use of phenylephrine infusions in specific instances of cerebral ischemia, as shown on an electro-encephalogram, results in low perioperative rates of both myocardial infarction (MI) and cerebral infarction remains unclear. We studied 171 CEAs done under general anesthesia performed with selective shunting based on the identification of cerebral ischemia by a two-channel computerized electroencephalographic monitor. The use of a phenylephrine infusion was restricted to the following instances of cerebral ischemia: 1) ischemia associated with hypotension that did not resolve within 2 minutes of decreases in anesthetic administration and treatment with fluid and/or colloid; 2) ischemia poorly or slowly responsive to shunt placement, accompanied by either hypo- or normotension; and 3) ischemia poorly or slowly responsive to removal of the carotid clamp, accompanied by either hypo- or normotension. Two non-Q wave MIs (1.2%) occurred, both nonfatal. There were two cerebral infarctions (1.2%) and three deaths not related to MI (1.8%). Based on these findings, in order to decrease the incidence of both MI and cerebral infarction after general anesthesia for CEA, we recommend the restrictive use of phenylephrine-induced hypertension for specific instances of slowly or poorly reversible cerebral ischemia, as shown on the electroencephalogram.