BACKGROUND Anaesthesia reduces mean arterial pressure (MAP), and to preserve organ perfusion, vasopressors are often used to maintain MAP above 60 mmHg. Cognitive dysfunction is common following major surgery and may relate to intra-operative cerebral hypoperfusion. OBJECTIVE The aim of this study was to evaluate whether internal carotid artery (ICA) blood flow increases when MAP is kept higher than 60 mmHg using noradrenaline. DESIGN A randomised, cross-over trial. SETTING Department of Anaesthesia, Rigshospitalet, Copenhagen, Denmark, from December 2017 to April 2018. PATIENTS Patients with median [IQR] age 71 [63 to 75] years underwent pancreaticoduodenectomy (n = 19), total pancreatic resection (n = 1) or gastro-entero anastomosis (n = 2) during combined propofol-remifentanil and thoracic epidural anaesthesia. INTERVENTION MAP was maintained between 60 to 65, 70 to 75 and 80 to 85 mmHg, in a random order, by noradrenaline infusion at a stable level of anaesthesia. MAIN OUTCOME MEASURES Primary outcome was change in ICA flow at MAP 60 to 65 vs. 80 to 85 mmHg. Secondary outcomes were change in ICA flow at MAP 60 to 65 vs. 70 to 75 and 70 to 75 vs. 80 to 85 mmHg. Duplex ultrasound evaluated ICA flow. RESULTS A (mean +/- SD) increase in MAP from 62 +/- 1 to 82 +/- 1 mmHg elevated ICA flow from 196 +/- 53 to 226 +/- 61 ml min(-1)(mean difference 31 ml min(-1); 95% CI 19 to 42;P <0.0001). An increase in MAP from 62 +/- 1 to 72 +/- 1 mmHg elevated ICA flow to 210 +/- 52 ml min(-1)(P = 0.0271) and ICA flow increased further (P = 0.0165) when MAP was elevated to 82 +/- 1 mmHg. CONCLUSION During combined propofol-remifentanil and thoracic epidural anaesthesia, ICA flow increased by approximately 15% when the MAP was elevated from about 60 to 80 mmHg. Treatment of a reduction in MAP brought about by anaesthesia seems to enhance ICA flow.