Background: Data from patient questionnaires reveal that the intensity of postoperative pain is widely underestimated. Insufficient pain control may contribute to impaired short- and long-term outcome. Preoperative administration of methadone might potentially improve postoperative pain control due to its long pharmacological half-life.
Methods: The aim of this study was to evaluate the effect of a single dose of methadone administered at anesthesia induction on postoperative analgesic requirements in ASA I-III patients after moderate-to-severely painful surgery scheduled for ≥90 minutes. Patients were randomized to receive either a single dose of methadone (0.2 mg/kg) or fentanyl (standard, 0.003 mg/kg) intravenously (IV) at anesthesia induction. For postoperative pain control, all study patients were accommodated with morphine on the basis of patient-controlled analgesia (PCA).
Results: Per-protocol analysis revealed that the median cumulative morphine consumption was significantly lower in patients receiving a single dose of methadone, in the Postanesthesia Care Unit (0 mg vs. 7 mg of morphine, P<0.01) and during the first 72 hours after surgery (19 mg vs. 35 mg of morphine, P<0.05 for all days). Fentanyl consumption during surgery (0.25 mg [0.1-0.425 mg] in the study group vs. 0.3 mg [0.15-0.45 mg] in the control group, P=0.4499) was comparable among groups. Median pain scores at rest and in motion, and patient satisfaction were also similar in both groups (95.7% vs. 89.3% of patients were satisfied in the study and control group, respectively) during follow-up on postoperative days 1-3.
Conclusions: A single dose of methadone administered at anesthesia induction prior to moderate-to-severely painful surgery is a possible strategy to reduce postoperative morphine consumption.