Intravenous clonidine fails to reduce postoperative meperidine requirements

To investigate the effect of an additional postoperative intravenous (IV) clonidine infusion on meperidine requirements in the early postoperative period.

Prospective, randomized, double-blind, placebo-controlled study.

Postoperative recovery room at a university medical center.

Sixty female patients who had undergone a cholecystectomy.

On first complaining of postoperative pain, 30 patients (clonidine group) received clonidine 150 micrograms IV over 30 minutes and an additional 150 micrograms of clonidine during the following 90 minutes. The other 30 patients (control group) were given identical volumes of 0.9% sodium chloride IV at identical time intervals. All patients received a patient-controlled analgesia device (initial dose, meperidine 16 mg; subsequent doses, meperidine 8 mg on demand; lockout time, 5 minutes; background infusion, meperidine 2.5 mg/hr).

Pain intensity was evaluated with a 101-point numerical rating scale. Blood pressure, heart rate (HR), respiratory rate, arterial hemoglobin oxygen saturation, and any side effects were recorded. There were no significant differences between the clonidine and control groups with respect to postoperative pain. The patients in the clonidine group required a total meperidine dose of 62.7 +/- 4.9 mg, compared with 70.4 +/- 3.9 mg in the control group (mean +/- SEM; not a significant difference). Systolic blood pressure and HR were significantly lower from 20 to 120 minutes and from 30 to 120 minutes, respectively after the start of the clonidine infusion compared with the placebo. No patient had to be treated for hypotension or bradycardia. Serious side effects were not observed.

During the first 2 postoperative hours following cholecystectomy, postoperative meperidine intake could not be reduced by IV administration of clonidine 300 micrograms.