THE EFFECTS OF MEPERIDINE AND SUFENTANIL ON THE SHIVERING THRESHOLD IN POSTOPERATIVE-PATIENTS

Background: Meperidine (pethidine) reportedly treats postoperative shi vering better than equianalgesic doses of other EL-receptor agonists, The authors' first goal was to develop a method to accurately determin e postoperative shivering thresholds, and then to determine the extent to which meperidine and sufentanil inhibit postoperative shivering. M ethods: 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; pa tients were randomly assigned to each drug and concentration. The infu sion was continued throughout surgery and recovery. Anesthesia was mai ntained with nitrous oxide and isoflurane. Core temperatures were appr oximate to 34 degrees C by the end of surgery. The compensated core te mperature at which visible shivering and a 20% decrease in steady-stat e 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 thre shold was evaluated using linear regression. Results: End-tidal isoflu rane 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.[meper idine (mu g/ml)] + 36.2; r(2) = 0.64, P = 0.0005. Sufentanil also line arly decreased the shivering threshold: threshold (degrees C) = -7.8.[ sufentanil (ng/ml)] + 36.9; r(2) = 0.46, P = 0.02. Conclusions: At a g iven dose, sufentanil inhibited shivering 2,800 times better than mepe ridine. However, the equianalgesic ratio of these drugs is approximate ly 4,900, That is, meperidine inhibited shivering better than would be expected based on the equianalgesic potency ratio. These data are thu s consistent with clinical observations suggesting that meperidine ind eed possesses special antishivering activity.