Pilot study on the effect of tourniquet use on sufentanil pharmacokinetics.

Study Objective: To test our hypothesis that sequestration of sufentanil can occur during surgery when a pneumatic tourniquet is used.

Design: Prospective, randomized study.

Setting: Operating room and recovery room of a university hospital.

Patients: 16 ASA physical status I and II patients scheduled for orthopedic surgery with pneumatic tourniquet use.

Intervention: Patients were randomized to three groups. Sufentanil was given intravenously at 0.5 microg kg(-1) bolus at the same time that a constant infusion was started at 0.5 microg kg h(-1). In Group 1, continuous infusion of sufentanil was stopped when the tourniquet was released (n = 6). In Group 2, continuous infusion of sufentanil was stopped 15 minutes after tourniquet release (n = 6). In Group 3, as a control group, the sufentanil bolus was started after tourniquet inflation (n = 4).

Measurements: Plasma sufentanil concentrations were determined by radioimmunoassay. To compare pharmacokinetic results, a simulation of the sufentanil plasma concentrations was achieved.

Main Results: Exsanguination and inflation of the pneumatic tourniquet had no significant effect on pharmacokinetic results. In 75% of patients, a significant increase in sufentanil plasma concentration occurred between 30 and 60 minutes after tourniquet deflation in all three groups, probably as a result of patient mobilization. One respiratory distress event occurred in a Group 2 patient following extubation at 55 minutes after the end of the sufentanil infusion. The rebound of sufentanil concentration was higher in Group 2; it may be due to a reduced effect of the restoring circulation in the ischemic leg by a prolonged infusion after tourniquet deflation.

Conclusions: Using a pneumatic tourniquet induces transient changes in the pharmacokinetics of sufentanil. These changes may have clinical relevance during the first hour after tourniquet release.