Ketamine and lornoxicam for preventing a fentanyl-induced increase in postoperative morphine requirement.

Background: N-methyl-D-aspartate receptor antagonists and nonsteroidal anti-inflammatory drugs are believed to prevent opioid-induced hyperalgesia and/or acute opioid tolerance, which could cause an increase in postoperative opioid requirement. In this randomized, double-blind, placebo-controlled study, we investigated whether co-administration of ketamine or lornoxicam and fentanyl could prevent the increase of postoperative morphine requirement induced by fentanyl alone.

Methods: Ninety females undergoing total abdominal hysterectomy with spinal anesthesia were randomly assigned to six groups consisting of placebo (normal saline, C), fentanyl (three bolus of 1 microg x kg(-1), F), ketamine (infusion of 15 microg x kg(-1) x min(-1), K), ketamine and fentanyl (infusion of 15 microg x kg(-1) x min(-1) ketamine plus three bolus of 1 microg x kg(-1) fentanyl, FK), lornoxicam (one bolus of 8 mg, L), and lornoxicam and fentanyl (one bolus of 8 mg lornoxicam plus three bolus of 1 microg x kg(-1) fentanyl, FL). Cumulative morphine consumption, pain score, and adverse effects were recorded at 1, 3, 6, 12, 24, and 48 h postoperatively.

Results: Cumulative morphine consumption in Group F was significantly more than that in Group C at 3, 6, and 12 h postoperatively (P < 0.05). Postoperative cumulative morphine consumption was similar in Groups C, K, FK, L, and FL. No differences in postoperative pain scores were observed among groups. More patients in Groups K and FK had hallucinations during and/or after surgery than those in Group C (P < 0.05).

Conclusions: Our data suggest that the increase of postoperative morphine requirements induced by intraoperative administration of fentanyl could be prevented by ketamine or lornoxicam.