Prospective Evaluation Of Electroencephalography, Carotid Artery Stump Pressure And Neurological Changes During 279 Consecutive Carotid Endarterectomies Performed In Awake Patients

Sachinder S. Hans, MD and  O. Jareunpoon, MD
Department of Surgery, Vascular Surgery, St. John Macomb Hospital, Warren, MI

Objective: This study attempted to correlate neurological changes in awake patients undergoing carotid endarterectomies (CEA) using cervical block anesthesia (CBA) with electroencephalography (EEG) and measurement of carotid artery stump pressure (SP).
Methods: Continuous EEG monitoring, and SP was measured prospectively in 279 consecutive patients undergoing CEA between April 1, 2003 to March 2006, under CBA.
Indications for CEA were asymptomatic, 70 % to 99 %, internal carotid artery stenosis in 79 % (n221), TIA’s including transient monocular blindness in 15 % (n41) and prior stokes in 6 % (n17). A 19-gauge butterfly needle was inserted into the common carotid artery (CCA) and mean CCA pressure before clamping, mean SP after carotid clamping and radial artery pressure was continuously measured in all patients. Selective shunting was performed when neurological events (contra lateral motor weakness, aphasia, decreased consciousness or seizures) occurred regardless of SP or EEG changes. During the same period, 29 patients underwent CEA under general anesthesia (GA) because of patient anxiety, hearing impairment, or language barrier and shunt placement was used on the basis of EEG changes. SP was measured in all patients undergoing CEA under GA.
Results: Four out of 29 patients (13.9%) undergoing CEA under GA required placement of a shunt. Shunt was necessary because of neurological changes in 11.4% (32/279) of all CEAs performed using CBA

Table 1: Need for shunt placement based on stump pressure:
CEA UNDER CERVICAL BLOCK ANESTHESIA
SP > 50 mmHg = 1.1 % (3/186)
SP < 50 mmHg = 31.1 % (29/93)
SP > 40 mmHg = 3 % (7/230)
SP < 40 mmHg = 51 % (25/49)

CEA, Carotid endarterectomy; SP, stump pressure,
Ischemic EEG changes were observed in 20 of 32 patients (60.6%) requiring shunt placement under CBA. Two out of 20 patients had SP > than 40 mmHg, SP was < 40 mmHg in remaining 18 patients with Ischemic EEG. Three patients had false positive EEGs (9%). Perioperative stroke/death rate was 4/308 (1.3%). All strokes occurred postoperatively and were unrelated to cerebral ischemia or lack of shunt placement.
Conclusion:
1). 11.4 % of patients required a shunt placement during CEA under CBA.
2). Shunt placement was necessary in 51 % of patients with SP below 40 mmHg.
3). EEG identified cerebral ischemia in only 60.6 % of patients undergoing CEA under CBA.