Effect of Phenylephrine and Ephedrine on Cerebral (Tissue) Oxygen Saturation During Carotid Endarterectomy (PEPPER): A Randomized Controlled Trail

Abstract

Introduction - Adequate blood pressure during carotid endarterectomy (CEA) is essential to preserve cerebral perfusion. To achieve and maintain adequate blood pressure intraoperative, short-acting vasopressor agents like phenylephrine or ephedrine can be used. Previous studies in healthy subjects revealed that besides a systemic hemodynamic effect, these vasopressors also affected frontal lobe cerebral tissue oxygenation (ScO2) showing a decrease after administration of phenylephrine.1,2 This decrease in ScO2 after phenylephrine administration is unwarranted in patients with jeopardized cerebral perfusion, like CEA patients. The aim of this study was to evaluate the impact of both phenylephrine and ephedrine on ScO2 during CEA. Methods - In this double blinded randomized controlled trial 29 patients underwent CEA under general anesthesia for > 70% symptomatic or asymptomatic stenosis. This number of patients matches the number of subjects required according to the power calculation, which suggested 14 patients for each vasopressor study arm.3 Patients were preoperative allocated randomly (1:1) by computer-generated randomization for receiving either phenylephrine or ephedrine in case intraoperative hypotension occurs. During CEA mean arterial pressure (MAP) was measured by radial artery line, placed on the arm with the highest preoperative systolic blood pressure. In case of a decreased MAP ³20% compared to (awake) baseline, patients received a bolus of either phenylephrine (50μg; N=14) or ephedrine (5mg; N=15). After administration the MAP, cardiac output, heart rate, stroke volume and ScO2 were measured. The chosen timeframe for data analysis was 120 seconds before, until 300 seconds after administration. Results - Both phenylephrine (70±9 to 99±22 mmHg; P<0.001; mean±SD) and ephedrine (75±11 mmHg to 109±19 mmHg; P<0.01) adequately restored the MAP. Heart rate did not change significantly after infusion of both vasopressors. However cardiac output was raised after administration of both, 15% and 14% for phenylephrine and ephedrine respectively. ScO2 did not change significantly after administration of either phenylephrine or ephedrine (from 73% to 71% and 72% to 71% respectively). Conclusion - Within this randomized prospective study, we did not observe a different response in ScO2 when MAP was corrected by either phenylephrine or ephedrine in patients who underwent CEA.