Comparative study of the analgesic effect of transcutaneous nerve stimulation (TNS); electroacupuncture (EA) and meperidine in the treatment of postoperative pain.

Seventy two patients, from 15 to 60 years old, in good physical status and submitted to surgery in the upper or lower abdominal, rectal or lumbar areas were studied. In the immediate postoperative period, they were randomly divided in three groups and each group was submitted to one of the following treatments: intravenous meperidine, transcutaneous nerve stimulation (TNS) or electroacupuncture (EA). Each treatment was divided in two phases with one hour interval between them. Each phase was constituted of 30 minutes of stimulation in case of TNS and EA and fractionated administration of meperidine in all groups. The pain level was evaluated through a visual analogue scale before and after each phase of treatment. The results were compared among groups and, on each group, between the phases of treatment. In all surgery types, the postoperative pain relief presented by TNS and EA groups of patients was greater than that of meperidine treated group. But, the analgesia presented by the EA treated group of patients lasted longer and increased with the repetition of treatment. The differences of behaviour of TNS and EA analgesia suggest that their neurochemical mechanisms may not be the same.