Multiple previous investigations have attempted to establish a correlation between intraoperative hypoperfusion and postoperative neurocognitive deficits. In a previous study of 50 consecutive patients undergoing shoulder arthroscopy in the BCP, regional cerebral tissue oxygen saturation (rSO2) was monitored intraoperatively using NIRS. The Repeatable Battery for the Assessment of Neuropsychological Status was administered to each patient pre- and postoperatively, as its sensitivity allows detection of mild cognitive impairment and it is validated to assess postsurgical cognitive changes. The incidence of intraoperative CDEs was 18% (9/50). They found no statistical significance in pre- versus postoperative Repeatable Battery for the Assessment of Neuropsychological Status either in composite scores or any of the subindices in either group.29 Cox et al used NIRS to monitor cerebral oxygenation saturation in 41 consecutive patients undergoing arthroscopic shoulder surgery in the BCP. Patients were randomized into two groups, and anesthetists aware of or blinded to NIRS data. The Montreal Cognitive Assessment, which has been shown to detect mild cognitive deficits, was used to assess cognitive function preoperatively, immediately postoperatively, and at 2 and 6 weeks postoperatively. Overall, 7 patients (17.5%) experienced a CDE, 5 (25%) in the aware group, and 2 (10%) in the blinded group. There was no significant difference in Montreal Cognitive Assessment scores between the aware and blinded groups preoperatively (27.9.1 versus 28.2; P = 0.436), immediately postoperatively (26.1 versus 26.2; P = 0.778), 2 weeks postoperatively (28.0 versus 28.1; P = 0.737), or 6 weeks postoperatively (28.5 versus 28.4; P = 0.779) (Cox 29396097).14 Laflam and colleagues performed a comparative investigation of 109 patients undergoing shoulder surgery in the BCP and 109 patients in the lateral decubitus position using regional cerebral oxygen saturation (rScO2) monitored with NIRS. Psychometric testing, with the National Institutes of Health Stroke Scale, Rey Auditory Verbal Learning Test, Controlled Oral Word Association Test, Symbol Digits Modalities Test, Trail Making B, and Grooved PegBoard Test, was performed before surgery and then 7 to 10 days and 4 to 6 weeks after surgery. A composite cognitive outcome was determined as the Z-score. Serum biomarkers that are associated with brain injury—S100β, neuron-specific enolase, and glial fibrillary acidic protein—were measured at baseline, after surgery, and on postoperative day 1. After adjusting for baseline composite cognitive outcome, there was no difference in Z-score 7 to 10 days (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 two position groups.21
Our previous review highlighted the abundance of literature reporting previously healthy patients who develop neurologic complications after arthroscopic shoulder surgery in the BCP.1 The BCP has been implicated as a source of cerebral hypoperfusion and subsequent cerebral ischemia. The exact etiology of central nervous system injuries is incompletely understood and is thought to be multifactorial. However, hypoperfusion is thought to be the determining factor of poor neurologic outcome.1,3 Reports of neurologic complications have revealed a need for heightened vigilance, alternative anesthesia techniques, and improved monitoring.1 In this literature review, we sought to update the incidence of intraoperative CDEs, to investigate the relationship of CDEs to neurocognitive complications, and to review recent reported cases of neurocognitive complications, all in patients who have undergone arthroscopic shoulder surgery in the BCP.
Neurocognitive complications after shoulder arthroscopy in the BCP are exceedingly rare but potentially catastrophic events that may affect patients without preexisting cerebrovascular risk factors. A previous systematic review of 24,701 cases reported the overall incidence of neurologic deficits after arthroscopy in the upright position to be 0.004%.1 The severity, frequency, and duration of hypoperfusion that cause cerebral ischemia and subsequent neurocognitive deficits have yet to be defined in arthroscopic shoulder surgery. Multiple previous reports have failed to establish a correlation between intraoperative CDEs and postoperative neurocognitive deficits. Large prospective clinical studies and further preclinical research are still needed to understand the clinically significant thresholds of magnitude, duration, and frequency of intraoperative CDEs to clearly establish a relationship with postoperative neurocognitive complications. Such large studies are also needed to further illuminate modifiable patient risk factors and to establish a system of sensitive, safe, and costeffective cerebral perfusion monitoring. Existing literature suggests that accurate intraoperative monitoring of cerebral perfusion may improve patient safety.
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