[Do morphines improve the quality of analgesia with local anesthetics?]

Use of opioids for regional anaesthesia aims to improve the quality and to enhance the duration of local anaesthetics-induced analgesia, and also to reduce the rate of adverse effects due to these agents. Experimental data give evidence for a synergistic effect between local anaesthetic and opiates at the spinal level (dorsal root entry zone). A lot of clinical studies have shown the improvement of analgesia when opioids are added to local anaesthetics, by the subarachnoid as well as by the epidural route. The most frequent associations in use are fentanyl-bupivacaine and morphine-bupivacaine. The efficacy of these associations by peripheral perinervous routes is more controversial. In any cases, one must be aware of the incidence of potential side-effects of opioids and, consequently, of the need for a close clinical monitoring of the patients, at least for the duration of action of the agent injected by the spinal or the epidural route.