ABSTRACT
BACKGROUND: The aim of the study was to evaluate postoperative analgesia and safety of wound instillation of ropivacaine either by a single dose or a patient-controlled regional anaesthesia (PCRA) technique. METHODS: In 40 patients undergoing arthroscopic subacromial decompression the surgeon placed a catheter into the subacromial space at the end of the operation. In Phase I (10 patients), ropivacaine 250 mg was injected twice within 1 h. In Phase II, 30 patients were randomised into three groups: group prilocaine-ropivacaine (PR) = 20 ml of 1% prilocaine-epinephrine injected preoperatively into the subacromial bursa + 20 ml of 0.5% ropivacaine infused in the catheter postoperatively; group saline-ropivacaine (SR) = saline-epinephrine (20 ml) preoperatively + 0.5% ropivacaine as in group PR; group saline-saline (SS) = saline-epinephrine (20 ml) preoperatively + saline postoperatively. The PCRA pump was filled with local anaesthetic or saline to allow boluses of 10-ml each, maximum one bolus/h, via the catheter. Pain relief, side-effects and venous plasma concentration of ropivacaine were evaluated during a 24-h-test period. RESULTS: The free plasma concentration of ropivacaine was 0.12 + 0.041 mg l-1 in Phase I. No adverse effects were seen. In Phase II pain at rest and on movement was lower in group PR than in group SS during the first 30 min postoperatively (P < 0.05). Group PR had the lowest morphine consumption (P < 0.05). Five to seven boluses were administered via the PCRA-pump, and 20 min after administration of the study solution, pain was lower in groups PR and SR compared with group SS (P < 0.001). CONCLUSIONS: Preoperative intrabursal prilocaine with epinephrine + postoperative subacromial administration of ropivacaine by PCRA-technique provided the most effective analgesia with no major side-effects. The free plasma concentrations of ropivacaine were far below toxic concentrations.
