The effects of meperidine and sufentanil on the shivering threshold in postoperative patients

Background: Meperidine (pethidine) reportedly treats postoperative shivering better than equianalgesic doses of other EL-receptor agonists, The authors' first goal was to develop a method to accurately determine postoperative shivering thresholds, and then to determine the extent to which meperidine and sufentanil inhibit postoperative shivering. Methods: A computer-controlled infusion was started before operation in 30 patients, with target plasma concentrations of 0,15, 0.30, or 0.60 mu g/ml meperidine or 0.1, 0.15, or 0.2 ng/ml sufentanil targeted; patients were randomly assigned to each drug and concentration. The infusion was continued throughout surgery and recovery. Anesthesia was maintained with nitrous oxide and isoflurane. Core temperatures were approximate to 34 degrees C by the end of surgery. The compensated core temperature at which visible shivering and a 20% decrease in steady-state oxygen consumption was recorded identified the shivering threshold. A blood sample for opioid concentration was obtained from each patient at this time. The ability of each opioid to reduce the shivering threshold was evaluated using linear regression. Results: End-tidal isoflurane concentrations were <0.2% in each group at the time of extubation, and shivering occurred approximate to 1 h later. Meperidine linearly decreased the shivering threshold: threshold (degrees C)= -2.8.[meperidine (mu g/ml)] + 36.2; r(2) = 0.64, P = 0.0005. Sufentanil also linearly decreased the shivering threshold: threshold (degrees C) = -7.8.[sufentanil (ng/ml)] + 36.9; r(2) = 0.46, P = 0.02. Conclusions: At a given dose, sufentanil inhibited shivering 2,800 times better than meperidine. However, the equianalgesic ratio of these drugs is approximately 4,900, That is, meperidine inhibited shivering better than would be expected based on the equianalgesic potency ratio. These data are thus consistent with clinical observations suggesting that meperidine indeed possesses special antishivering activity.