The Influence of Barbiturates on Cerebral Metabolism in Patients with Borderline Cerebrovascular Reserve during Intraoperative Transient Carotid Occlusion

Sixty patients with borderline or frank insufficiency of their cerebrovascular reserve undergoing carotid endarterectomy were given enough short acting barbiturates, during cross clamping of the internal carotid artery, to cause EEG burst suppression. Arterial and venous concentrations of lactate were measured in blood samples taken before, 30 min after occulsion of the artery and 10 min after reperfusion. The amount of lactate produced depended on the length of time of burst suppression; the shorter it lasted, the larger the amount of lactate produced. Only in patients with the shortest burst suppression times did the blood lactate levels rise above normal levels. The lactate levels can be used as indicators of how effective barbiturates are being in preventing ischaemia during the time of carotid artery occlusion.