Background: To minimize the incidence of intraoperative stroke following carotid endarterectomy (CEA) under general anesthesia, blood pressure (BP) is suggested to be maintained between "awake baseline" BP and 20% above. However, there is neither a widely accepted protocol nor a definition to determine this awake BP. In this study, we analyzed the BP during hospital admission in the days before CEA and propose a definition of how to determine awake BP.
Methods: In our cohort of 1180 CEA-patients, all noninvasive BP measurements were retrospectively analyzed. BP was measured during preoperative outpatient screening (POS), the last three days before surgery at the ward and in the operating room (OR) directly before anesthesia. Primary outcome was the comparability of all these preoperative BP measurements. Secondary outcome was the comparability of preoperative BP measurements stratified for postoperative stroke within 30 days.
Results: POS BP (148±22/80±12 mmHg [mean arterial pressure, MAP: 103±14 mmHg]) and the BP measured on the ward 3, 2, 1 days before surgery and on the day of surgery (146±25/77±13 [MAP: 100±15]), (142±23/76±13 [MAP: 98±15]), (145±23/76±12 [MAP: 99±14]) and (144±22/75±12 mmHg [MAP: 98±14]) were comparable (all P=NS). However, BP in the OR directly before anesthesia was higher, (163±27/88±15 mmHg [MAP: 117±18mmHg]) (P<0.01 vs. all other preoperative moments). A significant higher preinduction systolic BP and MAP was observed in patients suffering a stroke within 30 days compared to patients without (P=0.03 and 0.04 respectively).
Conclusions: Awake BP should be determined by averaging available BP values collected preoperatively on the ward and POS. BP measured in the OR directly before induction of anesthesia overestimates "awake" BP; and therefore, it should not be used.