Efficacy of Augmenting a Subacromial Continuous-infusion Pump with a Preoperative Interscalene Block in Outpatient Arthroscopic Shoulder Surgery: a Prospective, Randomized, Blinded, and Placebo-controlled Study

Purpose: This study's purpose was to determine the effectiveness of adding a preoperative interscalene brachial plexus block to standard postoperative management, including oral narcotics and a subacromial bupivacaine infusion pump, after arthroscopic shoulder surgery.

Methods: After performing a prospective power analysis and obtaining institutional board approval, we conducted a randomized placebo-controlled trial of 53 patients separated into a preoperative interscalene brachial plexus group and a control group. Group 1 received an interscalene block with 30 mL of 0.5% ropivacaine. Group 2 received a placebo with 10 mL of saline solution. All patients postoperatively received an arthroscopically placed subacromial infusion pump catheter for 72 hours and oral narcotics. Pain scores on a visual analog scale (VAS) and narcotic pill use were recorded at 6, 12, 20, 32, 40, 52, 60, 72, and 80 hours.

Results: Preoperative pain scores between groups were not significant (P > .05). A statistically significant difference was found for decreased pain scores at 6 hours after discharge in patients receiving an interscalene block (P = .001) (VAS of 30.9 in group 1 v 61.8 in group 2). There was also a decrease in the number of narcotic pills taken at the 6-hour time interval (P = .1) (0.6 pills v 1.1 pills). Group 1 had a rebound phenomenon 20 hours after discharge. Pain scores spiked as the effects of the block wore off (P = .08) (net change in VAS score increase, 25.0 v 10.3). No other statistical or clinical differences were observed.

Conclusions: The addition of a preoperative interscalene block to a postoperative subacromial infusion pump provided significant improvement of pain control only at 6 hours after discharge. Twelve hours after discharge, this benefit had disappeared. A rebound phenomenon of increased pain at 20 hours was seen after the interscalene block had worn off. After 20 hours, no statistically significant or clinically applicable differences were found.

Level Of Evidence: Level I, randomized controlled trial.