Blood pressure management during beach chair position shoulder surgery: What do we know?

One of the surgical procedures most commonly performed in North America is arthroscopic repair of the shoulder joint. In the United States, approximately two-thirds of these patients undergo anesthesia and surgery in the sitting or beach chair position (BCP). Although the BCP offers several advantages for the surgeon, including reduced risk of neurovascular trauma, ease of conversion to an open approach, and excellent intra-articular visualization, the sitting position introduces several challenges for the anesthesiologist and potential risks to the patient. Recent reports have described catastrophic neurologic injuries occurring in otherwise healthy patients during shoulder surgery in the sitting position. The authors of these reports hypothesized that improper blood pressure management resulted in reductions in cerebral perfusion pressure which led to central nervous system ischemia and injury. At the present time, however, several important questions about ‘‘best practices’’ for blood pressure management in the BCP remain unanswered. In this issue of the Journal, the investigations by YaDeau et al. and Trentman et al. provide important data in this ongoing debate about the prevalence, risk factors, and potential consequences of hypotension during shoulder surgery in the sitting position. The incidence of ischemic brain or spinal cord injury following shoulder surgery in the BCP is unknown. In 2003, Bhatti and Enneking reported that a patient developed visual loss and ophthalmoplegia after shoulder surgery. In 2005, Pohl and Cullen described four cases of severe brain and spinal cord injury in this patient population. In a 2009 survey of 287 members of the American Shoulder and Elbow Surgeons Society (93 responses), eight cases of cerebral vascular events after shoulder surgery were reported, all of which occurred in the sitting position. An analysis of the American Society of Anesthesiologists Closed Claims database for new onset cervical cord injuries published this year revealed that 24% of the events occurred in patients having surgery in the sitting position. It is likely that the incidence of these complications is significantly underreported, as surgeons and anesthesiologists may be reluctant to publish cases where otherwise healthy patients suffered severe neurologic injuries. Through personal communications, the authors of this editorial are aware of eight additional cases of central nervous system injury following BCP surgery that have not been reported in the literature. The Anesthesia Patient Safety Foundation (APSF) has now funded a national registry, the Neurologic Injury after Non-Supine Shoulder Surgery (NINSS) registry (http://depts.washington.edu/asaccp/NINS/ index.shtml), to establish the incidence of central nervous system injury and determine probable causative factors. The adverse neurologic events reported thus far were attributed most commonly to inadequate cerebral perfusion secondary to intraoperative hypotension. Significant hemodynamic changes occur when the patient’s position is changed from supine to sitting. In awake subjects, upright positioning activates the sympathetic nervous system, producing increases in systemic vascular resistance (3040%) and systemic blood pressure (10-15%) and reductions in cardiac output (15-20%). Under general anesthesia, baroreceptor responses are blunted, resulting in an attenuated increase in systemic vascular resistance, a decrease in mean arterial pressure, and a greater reduction in cardiac output compared with the awake state. Not surprisingly, G. S. Murphy, MD (&) J. W. Szokol, MD Department of Anesthesiology, NorthShore University HealthSystem, University of Chicago Pritzker School of Medicine, 2650 Ridge Avenue, Evanston, IL 60201, USA e-mail: dgmurphy2@yahoo.com