Intraoperative blood pressure and cardiac complications after aneurysmal subarachnoid hemorrhage: a retrospective cohort study.

Abstract

Previous studies report that intraoperative hypotension worsens outcomes after aneurysmal subarachnoid hemorrhage (aSAH). However, the hypotensive harm threshold for major adverse cardiovascular events (MACE) remains unclear. The authors included aSAH patients who had general anesthesia for aneurysmal clipping/coiling. MACE were defined by a composite of acute myocardial injury, acute myocardial infarction, and other cardiovascular complications identified by electrocardiogram and echocardiography. The authors initially used logistic regression and change-point analysis based on the second derivative to identify mean arterial pressure (MAP) of 75mmHg as the harm threshold. Thereafter, our major exposure was MAP below 75mmHg characterized by area, duration, and time-weighted average. The area below 75mmHg represents the severity and duration of exposure and was defined as the sum of all areas below a specified threshold using the trapezoid rule. Time-weighted average MAP was derived by dividing area below the threshold by the duration of anesthesia. All analyses were adjusted for baseline risk factors including age greater than 70 years, female sex, severity of intracerebral hemorrhage, history of cardiovascular disease, and preoperative elevated myocardial enzymes. Among 1029 patients enrolled, 254 (25%) developed postoperative MACE. Patients who experienced MACE were slightly older (59±11 vs. 54±11 years), were slightly more often women (69 vs. 58%), and had a higher prevalence of cardiovascular history (65 vs. 47%). Adjusted cardiovascular risk increased nearly linearly over the entire range of observed MAP. However, there was a slight inflexion at MAP of 75mmHg. MACE was significantly associated with area [adjusted odds ratios (aOR) 1.004 per 10mmHg.min, 95% CI: 1.001-1.007, P =0.002), duration (aOR 1.031 per 10min, 95% CI: 1.009-1.054, P =0.006), and time-weighted average (aOR 3.516 per 10mmHg, 95% CI: 1.818-6.801, P <0.001) of MAP less than 75mmHg. Lower blood pressures were associated with cardiovascular complications over the entire observed range, but worsened when MAP was less than 75mmHg. Pending trial data to establish causality, it may be prudent to keep MAP above 75mmHg in patients having surgical aSAH repairs to reduce the risk of MACE.