Blood pressure response to combined general anaesthesia/interscalene brachial plexus block for outpatient shoulder arthroscopy

Abstract

Background: Shoulder surgery is often performed in the beach-chair position, a position associated with arterial hypotension and subsequent risk of cerebral ischaemia. It can be performed under general anaesthesia or with an interscalene brachial plexus block, each of which has specific advantages but also specific negative effects on blood pressure control. It would be worthwhile to combine the advantages of the two, but the effects of the combination on the circulation are not well investigated. We studied blood pressure, heart rate, and incidence of adverse circulatory events in patients undergoing shoulder surgery in general anaesthesia with or without an interscalene block. Methods: Prospective, randomised, blinded study in outpatients (age 18 to 80 years) undergoing shoulder arthroscopy. General anaesthesia was with propofol/opioid, interscalene block with 40 ml 1% mepivacaine. Hypotension requiring treatment was defined as a mean arterial pressure < 60 mmHg or a systolic pressure < 80% of baseline; relevant bradycardia was a heart rate < 50 bpm with a decrease in blood pressure. Results: Forty-two patients had general anaesthesia alone, 41 had general anaesthesia plus interscalene block. The average systolic blood pressure under anaesthesia in the beach-chair position was 114 +/- 7.3 vs. 116 +/- 8.3 mmHg (p = 0.09; all comparisons General vs. General-Regional). The incidence of a mean arterial pressure under 60 mmHg or a decrease in systolic pressure of more than 20% from baseline was 64% vs. 76% (p = 0.45). The number of patients with a heart rate lower than 50 and a concomitant blood pressure decrease was 8 vs. 5 (p = 0.30). Conclusion: One can safely combine interscalene block with general anaesthesia for surgery in the beach-chair position in ASA I and II patients.