Influence of blood pressure on internal carotid artery blood flow during combined propofol-remifentanil and thoracic epidural anesthesia.

Abstract

Anesthesia often reduces mean arterial pressure (MAP) to a level that may compromise cerebral blood flow. We evaluated whether phenylephrine treatment of anesthesia-induced hypotension affects internal carotid artery (ICA) blood flow and whether anesthesia affects ICA flow and CO2 reactivity. The study included twenty-seven patients (65 ± 11 years; mean ± SD) undergoing esophageal resection (n = 14), stomach resection (n = 12), or a gastroentero anastomosis (n = 1) during combined propofol-remifentanil and thoracic epidural anesthesia. Duplex ultrasound evaluated ICA blood flow. Evaluations were before and after induction of anesthesia, before and after the administration of phenylephrine as part of standard care to treat anesthesia-induced hypotension at a MAP below 60 mmHg, and the hypocapnic reactivity of ICA flow was determined before and during anesthesia. Induction of anesthesia reduced MAP from 108 ± 12 to 66 ± 16 mmHg (P < 0.0001) and ICA flow from 340 ± 92 to 196 ± 52 mL/min (P < 0.0001). Phenylephrine was administered to 24 patients (0.1-0.2 mg) and elevated MAP from 53 ± 8 to 73 ± 8 mmHg (P = 0.0001) and ICA flow from 191 ± 43 to 218 ± 50 mL/min (P = 0.0276). Furthermore, anesthesia reduced the hypocapnic reactivity of ICA flow from 23 (18-33) to 14%/kPa (10-22; P = 0.0068). Combined propofol-remifentanil and thoracic epidural anesthesia affect ICA flow and CO2 reactivity. Phenylephrine partly restored ICA flow indicating that anesthesia-induced hypotension contributes to the reduction in ICA flow.