[Intraoperative analgesic effect of epidural ketamine, clonidine or dexmedetomidine for upper abdominal surgery.]

Low dose ketamine decreases nociception by blocking NMDA receptor channels. Alpha2-adrenergic receptor activation triggers intense analgesic response. This study aimed at evaluating the effects of epidural ketamine, clonidine and dexmedetomidine, in patients undergoing upper abdominal surgery.

Participated in this randomized double-blind study 70 patients of both genders, aged 18 to 50 years, physical status ASA I or II, submitted to subcostal cholecystectomy under general anesthesia associated to lumbar epidural anesthesia. Lumbar epidural anesthesia was randomly induced as follows:

20 mL of 0.75% ropivacaine and 1 mL of 0.9% saline solution (n = 10); Ketamine group: 20 mL of 0.75% ropivacaine and 0.5 mg.kg-1 ketamine (n = 20); Clonidine group: 20 mL of 0.75% ropivacaine and 1 mL clonidine (150 microg) (n = 20); Dexmedetomidine group: 20 mL of 0.75% ropivacaine and 2 microg.kg-1 dexmedetomidine (n = 20). Anesthesia was induced with etomidate, alfentanil and rocuronium and was maintained with isoflurane and alfentanil. Analgesia was evaluated by clinical signs and inhalational anesthetic inspired concentration was evaluated by anesthetic gases analysis during surgery.

All patients receiving ketamine, clonidine or dexmedetomidine had heart rate and systemic blood pressure decrease and have not required perioperative analgesic complementation. For the same patients, isoflurane inspired concentration varied from 0.5vol% to 1vol% and there were no clinical signs or responses suggesting inadequate anesthetic levels.

Epidural ketamine, clonidine or dexmedetomidine decreases alfentanil consumption and isoflurane inspired concentration in the intraoperative period of upper abdominal surgery.