First-pass pulmonary retention of sufentanil at three different background blood concentrations of the opioid.

Using a double-indicator technique, we have studied, in 10 patients undergoing aorto-coronary bypass surgery, first-pass pulmonary retention of sufentanil. Pulmonary retention was studied at three pseudo steady-state background blood concentrations of 2.8 (0.66), 6.9 (1.2) and 15.9 (2.6) ng ml-1, respectively, produced by a computer-controlled infusion. Mean first-pass pulmonary retentions at these concentrations were 68 (95% confidence intervals 62-73), 65 (60-70) and 60 (52-67)%, respectively. First-pass pulmonary retention of sufentanil was significantly lower at the highest background concentration compared with the lowest background concentration. First-pass pulmonary retention of sufentanil was partly saturable in the range of concentrations used for clinical purposes.