SUFENTANIL PLASMA-CONCENTRATIONS FOLLOWING LOWER-EXTREMITY TOURNIQUETRELEASE

Study Objective: To investigate whether release of a tourniquet on the lower extremity affects plasma concentrations of sufentanil, as previ ously demonstrated with fentanyl and midazolam. Design: Prospective. S etting: University tertiary-care institution with residency program. P atients: 20 ASA status I, II, and III patients undergoing total knee a rthroplasty under a tourniquet using a sufentanil, nitrous oxide, rela xant regimen. Interventions: Each patient received sufentanil 1 to 2 m u g/kg at induction of anesthesia and in 12.5 to 25 mu g increments as needed thereafter, until 15 minutes prior to tourniquet release. Meas urements and Main Results: Plasma sufentanil concentrations were deter mined before tourniquet inflation, immediately before tourniquet defla tion, and 1, 2, 5, 10, 20, 30, and 40 minutes following deflation. A 1 5% elevation of plasma sufentanil concentration above that predicted b y elimination pharmacokinetic defined a secondary peak. Although the a ggregate data did no indicate an overall statistically significant ris e in plasma concentrations after deflation, 9 (45%) patients exhibited a secondary peak in sufentanil plasma concentration following tourniq uet deflation (range of secondary peaks, 16% to 89% above predicted va lues). No patient experienced clinically significant respiratory depre ssion. Conclusion: Release of a tourniquet on the lower extremity may yield a detectable rise in plasma sufentanil concentration.