Effect of mandibular nerve block on postoperative analgesia in patients undergoing oropharyngeal carcinoma surgery under general anaesthesia.

BACKGROUND Postoperative analgesia after oropharyngeal carcinoma surgery remains poorly studied. This study investigates the effects of mandibular nerve block (MNB) with ropivacaine 10 mg ml(-1) in conjunction with general anaesthesia (GA) on postoperative analgesia after partial glossectomy or transmandibular lateral pharyngectomy. METHODS In a randomized double-blind study, 42 patients (21 in each group) received an MNB by the lateral extra-oral approach (MNB group) or a deep s.c. injection of normal saline (control group). Both groups received a standardized general anaesthetic. Postoperative analgesia included fixed dose of i.v. acetaminophen and morphine via a patient-controlled analgesia device. Consumption of morphine and supplemental analgesics and pain scores at rest were measured. RESULTS The mean cumulative morphine consumption was reduced by 56 and 45% at 12 and 24 h after operation in the MNB group. The administration of analgesic rescue medications was delayed in the MNB group. The visual analogue scale (VAS) pain scores were comparable in the two groups during the first 24 h. Adequate analgesia (mean VAS < or = 3) was observed throughout the study period in the MNB group, but only from 4 h after operation onwards in the control group. The number of patients who experienced severe pain (VAS > 7) during the first postoperative day was lower in the MNB group than in the control group (3 vs 10. respectively, P < 0.05). CONCLUSIONS In this study, MNB performed before GA for oropharyngeal carcinoma surgery improved postoperative analgesia, resulting in reduced morphine consumption at 24 h and severe pain in fewer patients.