Stroke, regional anesthesia in the sitting position, and hypotension: a review of 4169 ambulatory surgery patients.
Intraoperative hypotension is used to reduce surgical bleeding. Case reports of stroke after general anesthesia in the sitting position led us to collect data (patient demographics, medical risk factors for stroke, intraoperative hemodynamics) about the incidence of stroke after surgery in the sitting position. This study reviewed 4169 (3000 retrospective, 1169 prospective) ambulatory shoulder surgeries in the sitting position. For the prospective cohort, patients were queried postoperatively regarding stroke, with corroboration from 4 databases (anesthesia department quality assurance, hospital case management, state-reportable events, and hospital information system diagnostic code databases). For the retrospective cohort, rate of stroke was determined via the same 4 databases. No patient had a stroke (95% confidence interval, 0%-0.07%). Risk factors for perioperative stroke were present in 40% of patients. Brachial plexus nerve block with intravenous sedation was used for 95.7% (retrospective) and 99.8% (prospective) of the cohorts. Many patients (47%) experienced intraoperative hypotension by at least one definition: 40% (retrospective) and 30% (prospective) had at least a 30% decrease in mean arterial pressure; 27% (retrospective) and 24% (prospective) had a mean pressure less than 66 mm Hg; and 13% (retrospective) and 12% (prospective) had a systolic blood pressure of less than 90 mm Hg. No strokes were observed in 4169 patients. The estimated upper limit of the 95% confidence interval for stroke after regional anesthesia for shoulder surgery in the seated position is 0.07%, despite frequent incidence of hypotension.