Effect of single-shot interscalene block with less than 10 ml of local anesthetics on postoperative pain relief after arthroscopic rotator cuff reconstruction

Background : The effect of interscalene block on postoperative pain after arthroscopic rotator cuff reconstruction (ARCR) was evaluated. Methods : Eighty-four patients scheduled to undergo ARCR from April 2008 to March 2010 were assigned to a group receiving interscalene block with general anesthesia (Block group, n=49) and a group receiving general anesthesia solely (General group, n= 35). In the Block group, ultrasound-guided single-shot interscalene block was performed before induction of general anesthesia with 0.375% ropivacaine 7-10 ml. Postoperative pain intensity was recorded for 96 hours after the operation. Statistical analysis was performed with Mann-Whitney's U-test, and P<0.05 was considered to be significant. Results : Numerous rating scale (NRS) in the Block group was significantly lower than that in the General group immediately after the operation (median value : Block group=0, General group=6). Duration from the end of operation to the first administration of additional analgesics in the Block group (7 hours) was significantly longer than that in the General group (1 hour). NRS in the Block group tended to be higher than that in the General group from the night of the day of operation. Conclusions : Single-shot interscalene block with less than 10 ml of ropivacaine before ARCR reduced postoperative pain only for several hours after the operation.