[The combination of general anesthesia and interscalene block in shoulder surgery]

Abstract

Surgery on the shoulder often causes severe pain and, therefore, requires high doses of opiates. As postoperative pain is frequently treated inadequately, it is desirable to seek alternatives for providing effective analgesia. In a prospective study we examined the efficacy of balanced anesthesia consisting of general anesthesia combined with interscalene brachial plexus blockade for intra- and postoperative analgesia for operations on the shoulder. METHODS. Using the technique described by Winnie, interscalene block (ISB) was performed in 100 awake patients. After location of the brachial plexus by means of a peripheral nerve stimulator, we injected 40 ml bupivacaine 0.375%, after which general anesthesia (GA) was induced. At three predetermined points in time (recovery room, 8 h, and 24 h after the end of surgery), pain was evaluated by a visual analogue scale ranging from 0 to 10 and the extent of sensory blockade was tested by the pinprick method. The results of the pain scores and individual demands for analgesics were compared with a group of 22 patients who received only GA. Both groups were comparable in age, sex, and type of surgical procedure. RESULTS. We noted technical failure of the ISB in 8% of our patients. Side effects such as Horner's syndrome (18%), phrenic nerve paralysis (10%), and recurrent laryngeal nerve block (1%) were only temporarily observed during the action of the local anesthetics. During the surgical procedure, the group with ISB received a mean dose of 0.13 +/- 0.07 mg fentanyl versus 0.29 +/- 0.08 mg in the GA group (P less than 0.01) with equipotent doses of volatile anesthetics (1.0 to 1.5 MAC enflurane). Postoperative pain occurred for the first time in 39% of the patients given ISB later than 12 h after the end of surgery (average 8.7 +/- 5.9 h). In contrast, 95% of the patients with GA complained of pain in the recovery room. Pain measurement by the analogue scale clearly demonstrated the advantages of balanced anesthesia directly and 8 h after the operation (P less than 0.01). Even 24 h after the end of the surgical procedure the patients had better pain relief (P less than 0.05) in spite of the decreasing effect of the ISB. These significant differences led to the following results for postoperative treatment: 35% of the patients with ISB did not require additional analgesics during the first 24-h period after surgery, whereas 95% of those with GA requested analgesia. Only 32% of the ISB patients required opioids versus 86% with GA. The average duration of stay in the recovery room was reduced by 25% in the group with ISB (86 vs 134 min). In a final assessment, 84% of the patients were satisfied with the balanced anesthesia and only 5% were disappointed with the method. CONCLUSION. The combination of ISB and GA allows a reduction in intraoperative doses of opiates and facilitates postoperative pain management. Because of the low incidence of side effects, the lack of complications, and the high degree of patient acceptance, we recommend this type of balanced anesthesia for patients undergoing shoulder surgery.