What Is the Risk of Intraoperative Cerebral Oxygen Desaturation in Patients Undergoing Shoulder Surgery in the Beach Chair Position?

BACKGROUND: Previous studies have shown that intraoperative cerebral desaturation in patients undergoing shoulder surgery in the beach chair position varies widely, from 0% to 80%. To our knowledge, the risk of intraoperative cerebral desaturation is not known after all identified intraoperative modifiable physiologic parameters that influence cerebral blood flow have been controlled for. QUESTIONS/PURPOSES: (1) What is the risk of intraoperative cerebral desaturation during shoulder surgery with the patient in the beach chair position when patients received combined general anesthesia and an interscalene block, and what other factors associated with intraoperative cerebral desaturation can be identified? (2) Is intraoperative cerebral desaturation associated with 24-hour cognitive decline? (3) What factors are associated with intraoperative hypotension?
METHODS: Between April and December 2020, 51 patients underwent elective shoulder surgery in the beach chair position at one center. Nine patients were excluded: four patients refused to participate, two patients were unable to receive an interscalene brachial plexus block, and three patients were operated on in less than 70° upright position. A total of 42 patients (aged 63 ± 10 years, of whom 52% [22 of 42] were female) were prospectively recruited into this study. Each patient was diagnosed with a rotator cuff tear and underwent arthroscopic repair in the beach chair position, which was performed in an upright position of 70° to 80°. Near-infrared spectroscopy was used to monitor regional cerebral oxygen saturation. The mean arterial pressure was monitored and controlled so that it was more than 70 mmHg in patients without hypertension and within 20% from the baseline mean arterial pressure in patients with hypertension. All patients received the standardized anesthesia protocol, which consisted of an interscalene brachial plexus block and general anesthesia. Intraoperative cerebral desaturation was defined as a decrease in the regional cerebral oxygen saturation level of more than 20% from the baseline value that lasted longer than 15 seconds after induction of anesthesia. Patients' clinical characteristics such as age, sex, BMI, preoperative hemoglobin level, preexisting medical conditions, and continuing antihypertensive medications on the morning of surgery were analyzed to identify the association with intraoperative cerebral desaturation. We used the Montreal Cognitive Assessment to assess cognitive function at preoperative and 24 hours postoperative. Episodes of hypotension and its treatment after maximum head elevation were recorded. The patients' clinical characteristics were analyzed to determine their association with hypotensive events.
RESULTS: In this study, intraoperative cerebral desaturation occurred in 43% (18 of 42) of patients, and female sex was identified as an associated risk (odds ratio 4.3 [95% confidence interval 1.2 to 16.2]; p = 0.03). The median (interquartile range) duration of intraoperative cerebral desaturation was 19 minutes (5 to 38). There was no association between intraoperative cerebral desaturation and 24-hour postoperative cognitive decline (OR 0.6 [95% CI 0.1 to 2.4]; p = 0.44). Risk factors for intraoperative hypotension were a history of hypertension, regardless of whether or not the patient took antihypertensive drugs on the morning of surgery (OR 4.9 [95% CI 1.3 to 18.1]; p = 0.02), and dyslipidemia (OR 4.3 [95% CI 1.2 to 16.3]; p = 0.03).
CONCLUSION: The intraoperative cerebral desaturation risk in the beach chair position was high. Female sex was an intraoperative cerebral desaturation risk factor. However, there was no association between intraoperative cerebral desaturation and postoperative cognitive decline. Patients with hypertension and dyslipidemia are at risk of intraoperative hypotension after positioning. Further large-scale studies are required to identify intraoperative cerebral desaturation-associated adverse neurologic outcome. LEVEL OF EVIDENCE: Level II, therapeutic study.