THE USE OF METOPROLOL AND GLYCOPYRROLATE TO PREVENT HYPOTENSIVE BRADYCARDIC EVENTS DURING SHOULDER ARTHROSCOPY IN THE SITTING POSITION UNDER INTERSCALENE BLOCK/

Sudden profound hypotensive and/or bradycardic events (HBE) have been reported in >20% of patients undergoing shoulder arthroscopy in the si tting position under interscalene block anesthesia. Retrospective stud ies suggest that the administration of P-blockers is safe and may decr ease the incidence of these episodes. We performed a randomized, prosp ective study to evaluate prophylaxis of these events. One hundred fift y patients were randomized to one of three groups (placebo; prophylact ic metoprolol to achieve a heart rate <60 bpm or a maximal dose of 10 mg; or prophylactic glycopyrrolate to achieve a heart rate >100 bpm or a maximal dose of 6 mu g/kg) immediately after the administration of the interscalene block. Blood pressure control was achieved with TV en alaprilat as needed. The incidence of HBE was 28% in the placebo group versus 5% in the metoprolol group (P = 0.004). The rate of 22% in the glycopyrrolate group was not significantly different from placebo. Pr eoperative heart rate and arterial blood pressure, intraoperative seda tion score, IV fluids, and enalaprilat use were similar in those patie nts who had a HBE compared with those who did not. Many aspects of thi s clinical setting are similar to tilt-table testing for patients with recurrent vasovagal syncope, in which beta-adrenergic blockade with m etoprolol has also been shown to be effective. We conclude that the Be zold-Jarisch reflex is the most likely mechanism fur these events. Imp lications: Episodes of acute hypotension and bradycardia occur during shoulder arthroscopy in the sitting position under interscalene block. In this study, we demonstrate that metoprolol, but not glycopyrrolate , markedly decreases the incidence of these episodes when given prophy lactically immediately after the administration of the block.