Effect of preoperative oral sustained-release morphine sulfate on postoperative morphine requirements in elective...

Sustained-release morphine sulfate (SRMS) is a painkiller used in oncology. The purpose of our study was to assess its efficacy on postoperative morphine requirements in elective spine surgery. This was a placebo-controlled, randomized, double-blind study. Adults scheduled for spine surgery under general anesthesia were orally administered SRMS (30 mg) or a placebo 2 h before surgery. Primary endpoint was postoperative cumulated morphine consumption through patient-controlled analgesia (PCA) during the 12 h following extubation. Statistical analysis was performed using a sequential method, the triangular test. The study was stopped after the sixth analysis (51 patients had been included; placebo: 26, SRMS: 25). Age, weight, sex ratio, type of surgery, intra-operative sufentanil consumption, anesthesia duration and time to extubation were similar in the two groups. Morphine consumption through PCA during the 12 h following extubation was significantly lower in the SRMS group (mean +/- SD: 10.5 +/- 7.6 mg) compared with placebo group (15.6 +/- 6.0 mg, P = 0.016, sequential analysis). Corresponding unbiased median estimates were 10.6 and 15.8 mg in SRMS and placebo groups, respectively. Morphine consumption through PCA during the 24 h following extubation was also significantly lower in the SRMS group (15.9 +/- 12.7 mg) compared with the placebo group (23.8 +/- 10.9 mg, P = 0.032). Vigilance, nausea and respiratory rate 3 and 6 h after extubation were similar in the two groups. A preoperative oral administration of SRMS (30 mg) induces a 33% reduction of postoperative morphine requirements in patients scheduled for spine surgery without inducing side effects.