Pulmonary uptake of sufentanil during and after constant rate infusion

We have studied the pulmonary uptake of sufentanil in patients during and after a short infusion of the drug. We studied 10 patients undergoing elective coronary artery bypass surgery during anaesthesia with 0.4-0.8% enflurane, before surgery. Sufentanil 50 micrograms min-1 was given over 10 min by a constant rate infusion. During infusion and for 20 min thereafter, blood samples were obtained from the distal port of the pulmonary artery catheter and from a radial artery catheter. Uptake and release of sufentanil into and from the lungs were examined by mass balance and compartmental analyses. At the end of the infusion a mean of 48.9 (SD 18.6)% of the dose was retained in the lungs, and 20 min after infusion retention was 18.4 (22.4)%. Smokers had significantly higher pulmonary retention of sufentanil. The pulmonary volume of distribution of sufentanil, estimated from the two-compartment model, was 20.9 (7.7) litre. We conclude that pulmonary uptake of sufentanil is significant, if the drug is given as an infusion.