Vasopressin ameliorates hypotension induced by beach chair positioning in a dose-dependent manner in patients undergoing arthroscopic shoulder surgery under general anesthesia

BACKGROUND: The beach chair position (BCP) is associated with hypotension that may lead to cerebral ischemia. Arginine vasopressin (AVP), a potent vasoconstrictor, has been shown to prevent hypotension in BCP. It also improves cerebral oxygenation in different animal models. The present study examined the effect of escalating doses of AVP on systemic hemodynamics and cerebral oxygenation during surgery in BCP under general anesthesia. METHODS: Sixty patients undergoing arthroscopic shoulder surgery in BCP under general anesthesia were randomly allocated to receive either saline (control, n = 15) or three different doses of AVP (0.025, 0.05, or 0.075 U/kg; n = 15 each) 2 minutes before BCP. Mean arterial pressure (MAP), heart rate (HR), regional cerebral oxygen saturation (SctO(2)), and jugular venous oxygen saturation (SjvO(2)) were measured after induction of anesthesia and before (presitting in supine position) and after BCP. RESULTS: AVP per se given before BCP increased MAP, and decreased SjvO(2), SctO(2), and HR in all patients (P < 0.05 for all). BCP decreased MAP, the magnitude of which and hence the incidence of hypotension was decreased by AVP in a dose-dependent manner. While in BCP, every dose of AVP reduced the HR and SctO(2). Accordingly, it increased the incidence of cerebral desaturation (> 20% SctO(2) decrease from the baseline value) with no differences in SjvO(2) and the incidence of SjvO(2) < 50% or SjvO(2) < 40% among the groups. CONCLUSIONS: AVP ameliorates hypotension associated with BCP in a dose-dependent manner in patients undergoing shoulder surgery under general anesthesia. However, AVP may have negative effects on SctO(2) before and after BCP and on SjvO(2) before BCP.