Preventive analgesia in thoracic surgery: controlled, randomized, double-blinded study

Preventive analgesia is defined as a treatment that is commenced before the surgical procedure in order to diminish the physiological consequences of afferent nociceptive transmission caused by the procedure and prevent central sensitization. The analysis of randomized studies of preventive analgesia is controversial. The aim of this study was to check the analgesic efficacy of preoperative administration of dextromethorphan associated with intercostal nerve block with levobupivacaine in thoracotomy patients who refused or had a contraindication to epidural analgesia.

This study was a four-arm, double-blinded, randomized placebo-controlled trial. Patients were allocated following close block randomization into four arms: 'Group A' preoperative dextromethorphan and preoperative intercostal block (IB), 'Group B' preoperative placebo and preoperative IB, 'Group C' preoperative dextromethorphan and postoperative IB, 'Group D' preoperative placebo and postoperative block. The primary end-point was the cumulative morphine consumption (CMC) within the first 14 days after surgery.

A total of 400 patients were enrolled and 395 completed the study. There were no statistical differences among the groups in terms of demographic and surgical data; in contrast, preoperative quality-of-life scores were heterogeneous. The mean CMCs were as follows: Group A 111.4 mg, Group B 121.5 mg, Group C 126.8 mg, Group D 138.3 mg. Group A mean was lower than the maximum (P = 0.0001). The CMC value did not correlate with age, sex, body mass index, education, type of surgery, length or width of the incision and rib fracture. Postoperative functional data and post-thoracotomy syndrome prevalence were homogeneous; female gender resulted predictive for post-thoracotomy syndrome.

Results indicate that preoperative administration of dextromethorphan associated with preoperative IB with levobupivacaine provided preventive analgesia, decreasing analgesic administration during the early postoperative period compared with placebo and/or postoperative IB. This study failed in detecting any effect of preventive analgesia on functional items and post-thoracotomy syndrome.