Stroke, Regional Anesthesia in the Sitting Position, and Hypotension A Review of 4169 Ambulatory Surgery Patients Jacques T. YaDeau, MD, PhD,* Mary Casciano, MD,Þ Spencer S. Liu, MD,* Chris R. Edmonds, MD,* Michael Gordon, MD,* Jennifer Stanton, BS,* Raymond John, BA,* Pamela M. Shaw, BS,* Sarah E. Wilfred, BA,* and Maureen Stanton, RN* Background and Objectives: 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, med- ical risk factors for stroke, intraoperative hemodynamics) about the in- cidence of stroke after surgery in the sitting position. Methods: This study reviewed 4169 (3000 retrospective, 1169 pro- spective) 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 as- surance, hospital case management, state-reportable events, and hospi- tal information system diagnostic code databases). For the retrospective cohort, rate of stroke was determined via the same 4 databases. Results: No patient had a stroke (95% confidence interval, 0%Y0.07%). 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 pa- tients (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% (pro- spective) had a mean pressure less than 66 mm Hg; and 13% (retrospec- tive) and 12% (prospective) had a systolic blood pressure of less than 90 mm Hg. Conclusions: No strokes were observed in 4169 patients. The esti- mated 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. (Reg Anesth Pain Med 2011;36: 430Y435) I ntraoperative hypotension can be used to reduce surgical bleeding, 1 but may impair perfusion of vital organs. 2,3 In normal subjects, cerebral blood flow is thought to be maintained constant over a range of mean arterial pressure (MAP) values from 70 to 150 mm Hg, but the validity of this concept has been challenged. 4 An MAP of 60 mm Hg has been recommended as the lower limit of induced hypotension. 5 A review article sug- gested that, during induced hypotension, the systolic blood pressure (SBP) should not be decreased by more than 20% to 30% from baseline (to 80Y90 mm Hg in normal patients). 6 The beach-chair/barbershop position (nearly 90-degree up- right) is often requested for shoulder surgery. 7 Four cases of is- chemic brain or spinal cord injury after shoulder surgery in the beach-chair position have been attributed to altered brain per- fusion caused by postural hypotension and/or head and neck manipulation. 8 Based on case reports of neurologic catastro- phes presumed secondary to decreased cerebral perfusion, delib- erate hypotension in the sitting position has been condemned. 9 However, at the authors’ institution, hypotension is often used in the sitting position in combination with regional anesthesia, without apparent intraoperative strokes. Review of the literature did not reveal any recent large series or trials describing the incidence of stroke after regional anesthesia in the sitting posi- tion. A recent survey of orthopedic surgeons indicated the inci- dence of stroke to be 8/274,225, but this was based on surgeons’ recollection of events and reflected a variety of various anes- thetics and intraoperative positioning. 7 This combined retrospective and prospective cohort obser- vational study was performed to determine the incidence of stroke in ambulatory patients undergoing shoulder surgery with regional anesthesia, sedation, and spontaneous ventilation. METHODS Approval was obtained from the institutional review board of the Hospital for Special Surgery. For the retrospective limb, anesthesia records were obtained for consecutive ambulatory patients undergoing shoulder surgery in the sitting position at the Hospital for Special Surgery beginning from 2005 and working backward in time (to June 2004) until 3000 patients were iden- tified. A retrospective sample size of 3000 was selected because, in the absence of strokes, the upper limit of the confidence in- terval (CI) for stroke would be 3 per 3000 or 0.1% 10 ; 2005 was selected for the starting year because, at the time of study design, 2005 was the most recent year for which the quality assurance process and yearly reports were complete. All shoulder surgery procedures were conducted in the seated position during this period. Operating room records were reviewed to identify pa- tients who underwent a shoulder surgery that had been scheduled as ambulatory. Shoulder surgery patients were excluded if they were scheduled for overnight hospital admission. Patients ini- tially scheduled as ambulatory but subsequently admitted were kept in the study (intention-to-treat analysis was used). Prospectively gathered data were used to validate the ret- rospective data. The prospective limb was part of a larger pro- spective cohort study described in detail by Liu et al 11 ; the size ORIGINAL ARTICLE 430 Regional Anesthesia and Pain Medicine & Volume 36, Number 5, September-October 2011 From the *Department of Anesthesiology, Hospital for Special Surgery; and †Department of Anesthesiology, Weill Cornell Medical Center, New York, NY. Accepted for publication May 27, 2011. Address correspondence to: Jacques T. YaDeau, MD, PhD, Department of Anesthesiology, Hospital for Special Surgery, 535 E 70th St, New York, NY 10021 (e-mail: yadeauj@hss.edu). This work is attributed to the Department of Anesthesiology, Hospital for Special Surgery, New York, NY. This study was funded by the Hospital for Special Surgery Anesthesiology Department- Research and Education Fund. Portions of this work have been presented at the ASRA annual meeting in Phoenix, AZ, April 30 to May 3, 2009. There are no conflicts of interest to report for this study. Copyright * 2011 by American Society of Regional Anesthesia and Pain Medicine ISSN: 1098-7339 DOI: 10.1097/AAP.0b013e318228d54e Copyright © 2011 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.