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

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.

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.

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).

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