Hypotension after Induction of Anesthesia as a Predictor of Hypotension after Opening the Dura Mater during Emergency Craniotomy

Background: The subject of this study is intraoperative hypotension during the evacuation of acute subdural haematoma (ASH). We examined the association between the decrease in intraoperative blood pressure (BP) after the induction of anaesthesia and the decrease in BP after opening the dura mater. The second aim of this study was to assess the relationship between preoperative hypertension and the emergence of an intraoperative drop in BP. Methods: This was a retrospective cohort study on adult patients undergoing emergency craniotomy due to ASH. In total, 165 medical records from a 2-year period were analysed. The patients were divided into two groups: high blood pressure (HBP) (n = 89) and normal blood pressure (NBP) (n = 76). The HBP group included patients with hypertension in the preoperative period (systolic blood pressure (SBP) > 150 mmHg). The NBP group included patients with an SBP between 90 and 150 mmHg. Results: We observed a significant drop in blood pressure in two operational periods: after the induction of anaesthesia and after opening the dura mater. A highly relevant positive correlation was noted between the decrease in SBP after anaesthesia induction and the opening of the dura mater (p < 0.001). In the HBP group, after opening the dura mater, there was a 44% SBP decrease from the baseline value. Conclusions: The reduction in BP after the induction of anaesthesia is a predictor of a subsequent drop in BP after opening the dura mater during urgent surgery due to ASH. Patients with hypertension in the preoperative period of ASH tend to have a greater intraoperative drop in BP and worse outcomes.