Knowledge of these hemodynamic changes has led several authors to recommend additional intraoperative monitoring of cerebral perfusion. Monitoring techniques have included use of invasive blood pressure monitoring adjusted to brain level, cerebral oximetry using near infrared spectroscopy, and electroencephalography. However, the clinical relevance of intraoperative CDEs in isolation is not well understood.1,6,7,23 In addition, cost and availability of additional advanced monitoring likely factor into why it is not more commonly used. For this patient population, the severity, frequency, and duration of desaturation that causes cerebral ischemia and the relationship with postoperative neurocognitive deficits remain undefined.
The incidence of CDEs in patients being monitored with near infrared spectroscopy while undergoing elective arthroscopic shoulder surgery in the BCP varies widely, from 0% to 80% (mean, 41%).1,4,7,10,12,21 Magnitude and duration of cerebral ischemia required to produce neurocognitive dysfunction in this patient population remain unidentified as well. In conscious patients, a 20% reduction in frontal lobe oxygenation is associated with clinical manifestations of cerebral hypoperfusion, such as syncope.15,29 As none of the patients in the studies we reviewed experienced any sort of deficit, we cannot definitively state there is a correlation between CDE occurrence and neurocognitive deficit.
One limitation of our investigation is that it was a systemic review, and thus there was substantial heterogeneity in the methods and designs of the studies included in the analysis. Among the different series, there was variability in multiple aspects of the study design, including type of anesthetic, patient inclusion criteria, type of surgery, type of intraoperative cerebral perfusion monitoring, and type of neurocognitive testing. As a result, comparing the groups was difficult, and the generalizability of our findings may be limited. In addition, it is difficult to accurately establish incidence and comprehensively review these events because of the paucity of literature.
Conclusion
Neurocognitive complications after shoulder arthroscopy with the patient in the BCP are extremely rare but potentially devastating events that can affect healthy patients with no preexisting cerebrovascular risk factors. Our review indicated the incidence of permanent neurologic deficit after arthroscopy in the BCP may be as low as 0.004%. The exact etiology of such complications is not clear. Basic science research and large prospective studies are needed to identify the clinically relevant thresholds of magnitude, duration, and frequency of intraoperative CDEs in order to establish their relationship with postoperative neurocognitive complications. Such large studies may also elucidate modifiable patient-specific risk factors and establish the most sensitive, safe, and cost-effective intraoperative monitoring tools. Current literature suggests that accurate intraoperative monitoring of cerebral perfusion, alternatives to general anesthesia, and prudent use of intraoperative blood pressure control may improve patient safety.