Evaluation of morphine for patient controlled analgesia with the Infusor system after opiate-free locoregional anesthesia for osteotomy of the foot

Abstract

Efficacy and safety of a PCA protocol, without loading dose or background infusion, was investigated in 40 consenting patients after osteotomy of the foot. All patients had intrathecal lidocaine 5% 1.8 ml preoperatively. Postoperative pain relief was provided with morphine from a Baxter Travenol infusor with PC module. The morphine concentration was 2 mg/ml or 3 mg/ml. In order to reach the analgesic blood concentration as quickly as possible, the patients were instructed to start PCA from the very first moment pain occurred. The patients breathed room air. The nursing staff evaluated respiratory and cardiovascular parameters, pain and side effects. Although mean VAS scores were higher than 3 in the early postoperative phase, no supplementary analgesics were required. One patient had urine retention. One patient had a drop in blood pressure at the start of morphine, which was quickly restored with the administration of colloids. Oxygen saturations were lower (SpO2 < 95%) the first hours postoperatively, especially at the first assessment where no morphine was administered. Pain or relative hypovolaemia could be an explanation. Dry mouth and sleepiness were the most frequently reported side-effects, followed by dizziness, vomiting and nausea. Sweating and itching were less frequently reported. The occurrence of the side effects was the highest during the first postoperative day. We conclude that even when morphine is used in PCA without loading dose or background infusion after opiate-free locoregional analgesia, close monitoring is necessary for at least 5 hours.