Haemodynamics and cerebral oxygenation during arthroscopic shoulder surgery in beach chair position under general anaesthesia.

BACKGROUND: Patients undergoing surgery in beach chair position (BCP) are at risk of cerebral ischaemia. We determined the prevalence and risk factors of jugular venous bulb oxygen desaturation (SjvO(2)  < 50%) in BCP. It was also examined whether regional cerebral tissue oxygen saturation (SctO(2) ) measured by near-infrared spectroscopy and SjvO(2) are interchangeable for assessment of cerebral oxygenation.
METHODS: Fifty-six consecutive patients undergoing arthroscopic shoulder surgery in BCP were studied. Anaesthesia was intravenous with propofol and remifentanil (P/R) or inhalational with sevoflurane and 50% nitrous oxide (S/N) depending on provider choice. Mean arterial pressure (MAP), heart rate (HR), SjvO(2) , and SctO(2) were measured before (baseline; post-induction in supine position) and after the patients assumed BCP. Bland-Altman analysis was performed to measure the agreement between SctO(2) and SjvO(2) .
RESULTS: SjvO(2) , SctO(2) , MAP, and HR decreased significantly when patients were raised into BCP. Jugular desaturation occurred in 41% of patients (56% with P/R vs. 21% with S/N anaesthesia, P = 0.0077). Risk factors for the desaturation included P/R anaesthesia [adjusted odds ratio (aOR) 4.76, 95% confidence interval (CI) 1.34-16.95, P = 0.016] and MAP < 50 mmHg (aOR 3.85, 95% CI 1.21-12.25, P = 0.023). Bland-Altman analysis showed a mean difference of -8.9% with 95% limit of agreement between -40.0% and 23.0%. The percentage error [1.96 standard deviation/mean of the reference method] was 48.5%.
CONCLUSIONS: The incidence of jugular desaturation in BCP was 41%, and P/R anaesthesia and hypotension were associated with its occurrence while undergoing surgery under general anaesthesia. SctO(2) may not replace SjvO(2) for the determination of cerebral oxygenation.