Sufentanil plasma concentrations following lower extremity tourniquet release

To investigate whether release of a tourniquet on the lower extremity affects plasma concentrations of sufentanil, as previously demonstrated with fentanyl and midazolam.

Prospective.

University tertiary-care institution with residency program.

20 ASA status I, II, and III patients undergoing total knee arthroplasty under a tourniquet using a sufentanil, nitrous oxide, relaxant regimen.

Each patient received sufentanil 1 to 2 micrograms/kg at induction of anesthesia and in 12.5 to 25 microgram increments as needed thereafter, until 15 minutes prior to tourniquet release.

Plasma sufentanil concentrations were determined before tourniquet inflation, immediately before tourniquet deflation, and 1, 2, 5, 10, 20, 30, and 40 minutes following deflation. A 15% elevation of plasma sufentanil concentration above that predicted by elimination pharmacokinetics defined a secondary peak. Although the aggregate data did not indicate an overall statistically significant rise in plasma concentrations after deflation, 9 (45%) patients exhibited a secondary peak in sufentanil plasma concentration following tourniquet deflation (range of secondary peaks, 16% to 89% above predicted values). No patient experienced clinically significant respiratory depression.

Release of a tourniquet on the lower extremity may yield a detectable rise in plasma sufentanil concentration.