Hemodynamic monitoring during surgeries in beach chair position: What can a big picture teach us?

Excerpt

Of the 26 Million surgeries listed in the U.S. National Anesthesia Clinical Outcomes Registry (NACOR) from 2010 to 2015, Total Shoulder Arthroplasty (TSA), a frequently performed procedure, was listed 38,147 times. Patients undergoing TSA are usually placed in the beach chair position, which improves surgical conditions but at the price of decreased cerebral blood flow. Textbooks describe cerebral blood flow auto regulation as functioning with mean arterial pressure (MAP) 50–150 mm Hg. Problematically and widely unknown, the lower limit of 50 mm Hg for cerebral blood flow auto regulation is based on an investigation in pregnant women published in 1953 even if pregnancy is well known as a vasoplegic state. To decrease blood pressure, the subjects in this 60+ year old study received hydralazine, a cerebral vasodilator [1, 2]. Interestingly, only 1 year later, Moyer et al. reported symptoms of cerebral ischemia occurring at a MAP of 55 mm Hg [3]; nonetheless, 50 mm Hg became the standard reported value for the lower limit of cerebral blood flow auto regulation. …