Shoulder Surgery in the Beach Chair Position Is Associated with Diminished Cerebral Autoregulation but No Differences in Postoperative Cognition or Brain Injury Biomarker Levels Compared with Supine Positioning

Abstract

Background Although controversial, failing to consider the gravitational effects of head elevation on cerebral perfusion is speculated to increase susceptibility to rare, but devastating, neurologic complications after shoulder surgery in the beach chair position (BCP). We hypothesized that patients in the BCP have diminished cerebral blood flow autoregulation than those who undergo surgery in the lateral decubitus position (LDP). A secondary aim was to examine whether there is a relationship between patient positioning during surgery and postoperative cognition or serum brain injury biomarker levels. Methods Patients undergoing shoulder surgery in the BCP (n=109) or LDP (n=109) had mean arterial blood pressure (MAP) and regional cerebral oxygen saturation (rScO2) monitored with near-infrared spectroscopy. A continuous, moving Pearson’s correlation coefficient was calculated between MAP and rScO2, generating the variable cerebral oximetry index (COx). When MAP is in the autoregulated range, COx approaches zero because there is no correlation between cerebral blood flow and arterial blood pressure. In contrast, when MAP is below the limit of autoregulation, COx is higher because there is a direct relationship between lower arterial blood pressure and lower cerebral blood flow. Thus, diminished autoregulation would be manifest as higher COx. Psychometric testing was performed before surgery and then 7–10 days and 4–6 weeks after surgery. A composite cognitive outcome was determined as the Z-score. Serum S100β, neuron-specific enolase, and glial fibrillary acidic protein were measured at baseline, after surgery, and on postoperative day 1. Results After adjusting for age and history of hypertension, COx (p=0.035) was higher and rScO2 lower (p<0.0001) in the BCP group than in the LDP group. After adjusting for baseline composite cognitive outcome, there was no difference in Z-score 7 to 10 day (p=0.530) or 4 to 6 weeks (p=0.202) after surgery between the BCP and the LDP groups. There was no difference in serum biomarker levels between the 2 position groups Conclusions Compared with patients in the LDP, patients undergoing shoulder surgery in the BCP are more likely to have higher COx indicating diminished cerebral autoregulation and lower rScO2. There were no differences in the composite cognitive outcome between the BCP and LDP groups after surgery after accounting for baseline Z-score.

The Second ASRA Practice Advisory on Neurologic Complications Associated With Regional Anesthesia and Pain Medicine

“…Recent data and opinion suggest that the LLA for SCBF is likely closer to a MAP of 60 to 65 mm Hg rather than the classically understood MAP of 50 mm Hg. [119][120][121][122] Moreover, direct and surrogate measures of the LLA for cerebral blood flow in humans suggest that the LLA varies widely among subjects and, contrary to common belief, is usually not related to or predicted by baseline blood pressure. 121 There exists a "physiologic reserve" between the LLA and the blood pressure at which cellular injury or death actually occurs.…”

Daring discourse: is nerve block with sedation the safest anesthetic for beach chair position?

“…Consistent with previous studies, surgery in BCP with GA/PPV resulted in significantly lower rScO2 values and a higher rate of CDE, when compared with patients in lateral decubitus position. However, psychometric tests showed no difference in postoperative cognition in comparison to baseline values 40. These results call into question the clinical significance of CDE, since correlation with postoperative neurologic deficit was not demonstrated.…”

Anatomy and Pathophysiology of Spinal Cord Injury Associated With Regional Anesthesia and Pain Medicine

“…69 Another study noted that patients undergoing shoulder surgery frequently reached the cerebral LLA at a MAP of 65 to 70 mm Hg, especially when in the beach-chair (ie, semisitting) position (BCP). 70 Similarly, in a study of dogs administered spinal anesthesia and then acutely hemorrhaged, SCBF began to decrease at a MAP of 66 mm Hg. 74 Circumstantial support for the injurious role of hypotension can also be found in spinal deformity surgery, wherein the correction of hypotension has been reported to reverse electrophysiologic signs of spinal cord dysfunction.…”

“…[65][66][67] With regard to our evolving understanding of CNS LLA, previous animal studies suggested that SCBF is autoregulated within a MAP range of 50 to 60 mm Hg to 120 to 135 mm Hg, assuming (1) an intact blood-spinal cord barrier 50,68 and (2) the LLA for the spinal cord behaves in a similar manner as the LLA of the brain. In recent years, Drummond et al 66,67 and others 61,69,70 have challenged the previously accepted dictum of MAP 50 mm Hg representing a relevant and consistent cerebral LLA in humans and have instead presented evidence that cerebral LLA varies widely among individuals and is likely closer to 60 to 65 mm Hg in normotensive, unanesthetized adults. These experts remind us that CNS blood flow does not stop upon reaching the LLA but that there is a range between baseline MAP, the LLA, and the blood pressure below which irreversible cell damage occurs.…”

“…The duration of hypotension experienced by these patients was relatively limited (only 5%-7% of operative time [15-18 minutes]). [77][78][79] Laflam et al 70 reported in a prospective study that patients operated on in the BCP often experience diminished autoregulation over a wide range of MAP (70 mm Hg; interquartile range, 55-80 mm Hg), yet did not exhibit evidence of brain injury. Overall, these results can be interpreted as supporting the concept of a physiologic reserve that protects the vast majority of patients from injury, even when limited periods of low MAP occur at the brain or cervical spinal cord level while in the BCP.…”