Abstract
Objectives: Ketamine and dexamethasone have been reported to improve postoperative analgesia and chronic post-surgical pain. In patients undergoing inguinal hernia repair, we have compared the effects of each drug individually with their combination.
Patients and methods: Sixty male patients randomly distributed in three groups, received double-blind: (i) dexamethasone 8 mg, 1 h before surgery (Group D); (ii) a bolus of ketamine 0.5 mg/kg after endotracheal intubation (Group K); or (iii) their combination (Group DK). Anaesthesia was maintained with sevoflurane and remifentanil. Dexketoprofen (50 mg, i.v.), paracetamol (1 g, i.v.) and wound infiltration with bupivacaine were used before closing. In the recovery room, boluses of 25 mg of tramadol were administered every 15 min until a visual analogue scale (VAS) score of less than 3 was recorded. After discharge, ibuprofen plus paracetamol was used for analgesia. Postoperatively, we assessed pain intensity (VAS 0–10), tramadol consumption, and adverse events. Chronic post-surgical pain was evaluated 6 months after surgery by a personal interview, regarding the presence and characteristics of pain.
Results: Intra-operative remifentanil requirements were significantly lower in-group D (P = 0.04). In the recovery room, all groups had similar VAS values and tramadol requirements. None of the patients presented clinically relevant adverse effects. When evaluating chronic post-surgical pain, only 50 patients completed the interview and 36% (18 of 50) reported pain. Of these, 22% (4 of 50) had moderate pain (all in groups D and DK) and 78% (14 of 50) mild pain. All patients reporting pain in group K had mild pain, and a significantly lower number of them reported unpleasantness as their worst pain (P = 0.040).
Discussion: The combination of dexamethasone and ketamine does not seem to offer any advantages in the postoperative interval, suggesting a possible antagonism between these drugs. Of the three treatments studied, only ketamine had a discernible benefit in chronic post-surgical pain.