Internal carotid artery stump pressures during regional anesthesia

Abstract

Stump pressures during regional anesthesia were correlated with clinical signs of cerebrovascular insufficiency in the awake patient. Pa(CO2), Pa(O2) and mean systemic blood pressures were also measured in an attempt to determine whether adequate oxygenation, ventilation and blood pressure control could be maintained during regional anesthesia. None of the 7 patients whose stump pressures were less than 50 torr developed clinical symptoms of cerebrovascular insufficiency intraoperatively or postoperatively The mean Pa(O2) of this group was 132 torr an the mean Pa(CO2) 36 torr. Systemic blood pressure in this group increased from a mean control value of 90 torr to 105 torr intraoperatively. Pa(O2) decreased intraoperatively in one patient secondary to intraoperative pulmonary edema. Postoperatively, it was found that the patient had suffered silent myocardial infarction in the 3 mth prior to surgery. Two of the 12 patients with stump pressures greater than 50 torr developed clinical signs of cerebrovascular insufficiency, consisting of slurred speech, hemiplegia, and, in one patient, complete unresponsiveness. These changes were transient in one patient, but the other patient developed persistent hemiparesis. In both cases, stump pressures were greater than 70 torr. There was no associated hypercarbia or hypocarbia, and the mean blood pressure was not appreciably changed from control levels in these two patients.