INTRAVENOUS CLONIDINE FAILS TO REDUCE POSTOPERATIVE MEPERIDINE REQUIREMENTS

Study Objective: To investigate the effect of an additional postoperat ive intravenous (IV) clonidine infusion on meperidine requirements in the early postoperative period. Design: Prospective, randomized, doubl e-blind, placebo-controlled study. Setting: Postoperative recovery roo m at a university medical center. Patients: Sixty female patients who had undergone a cholecystectomy. Interventions: On first complaining o f postoperative pain, 30 patients (clonidine group) received clonidine 150 mug IV over 30 minutes and an additional 150 mug of clonidine dur ing the following 90 minutes. The other 30 patients (control group) we re given identical volumes of 0.9% sodium chloride IV at identical tim e intervals. All patients received a patient-controlled analgesia devi ce (initial dose, meperidine 16 mg, subsequent doses, meperidine 8 mg on demand; lockout time, 5 minutes; background infusion, meperidine 2. 5 mg/hr). Measurements and Main Results: Pain intensity was evaluated with a 101-point numerical rating scale. Blood pressure, heart rate (H R), respiratory rate, arterial hemoglobin oxygen saturation, and any s ide effects were recorded. There were no significant differences betwe en 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 grou p (mean +/- SEM; not a significant difference). Systolic blood pressur e and HR were significantly lower from 20 to 120 minutes and from 30 t o 120 minutes, respectively after the start of the clonidine infusion compared with the placebo. No patient had to be treated for hypotensio n or bradycardia. Serious side effects were not observed. Conclusions: During the first 2 postoperative hours following cholecystectomy, pos toperative meperidine intake could not be reduced by IV administration of clonidine 300 mug.