Transcranial doppler for carotid endarterectomy

Abstract

Patients with symptomatic high-grade carotid artery stenosis benefit from carotid endarterectomy. However, the operation is not without complications. The perioperative stroke rate varies from 2 to as much as 24% and depends on technique and patient selection. Seventy percent of perioperative strokes occur during the operation and are equally caused by cerebral ischaemia due to a low perfusion pressure and thromboembolic events related to surgical manipulation of the carotid artery. 1 The unique advantage of transcranial Doppler (TCD) for monitoring cerebral perfusion 2 is that it is noninvasive and at the same time detects changes in cerebral blood flow (CBF) immediately. 2'3 TCD provides the surgeon with a more accurate indentification of functional collateral flow behind the stenosis. 1 Thus, TCD gives prior warning of reduced flow before cerebral ischaemia results in changes on electroencaphelography (EEG) or somatosensory evoked potentials (SEPs). TCD also helps to identify a subgroup of patients preoperatively whose symptoms are due to a critically reduced cerebral perfusion rather than emboli. This condition is detected by the finding of an exhausted cerebral vascular reserve as assessed with carbon dioxide or acetazolamide responsiveness. 3 During the operation cerebral ischaemia can be prevented by the application of a carotid shunt. If TCD is not available, EEG or SEP provides information about ischaemia but cannot differentiate between low blood flow and an embolic event. Alternatively, a low pressure in the internal carotid artery during the crossclamp (the stump pressure) may be used to decide