Combination of oral clonidine and intravenous low-dose ketamine reduces the consumption of postoperative patient-controlled analgesia morphine after spine surgery.

OBJECTIVE

Because ketamine, clonidine, and morphine modulate nociceptive pain, coadministration of these drugs would augment the activity of postoperative analgesic drugs. The purpose of this study was to evaluate the effects of coadministration of ketamine and clonidine on postoperative morphine consumption in patients after spine surgery.

METHODS

The patients undergoing spine surgery were allocated randomly to one of the four study groups, which are as follows: group M (n = 12), intravenously (IV) administered patient-controlled analgesia (PCA) morphine alone; group MK (n = 12), IV-PCA morphine plus intra- and postoperative ketamine; group MC (n = 13), IV-PCA morphine plus oral clonidine premedication; group MCK (n = 12), IV-PCA morphine plus intra- and postoperative ketamine and clonidine premedication. The patients in the MC and MCK groups received 4 μg/kg clonidine orally, whereas those in the MK and MCK groups received IV bolus of ketamine (10 mg) at a rate of 2 mg/kg/hour during anesthesia. Patients were arranged to use IV-PCA mode for administration of drugs, which was programmed to deliver a bolus dose of 2-mg morphine (groups M and MC), or boluses of 2-mg morphine and 2-mg ketamine (groups MK and MCK). Scores of visual analog scale (VAS) for pain, morphine requirement, vital signs, nausea, sedation, and other side effects were followed up to 60 hours after surgery.

RESULTS

Although there were significant differences in VAS pain scores at rest 24-48 hours after the surgery, the VAS pain score at movement was similar among the groups. The number of PCA request and cumulative morphine requirement were significantly lower in the MCK group than in the M group.

CONCLUSION

This study results show that the administration of perioperative low-dose ketamine combined with clonidine premedication could reduce the consumption of postoperative PCA morphine following spine surgery.