FIRST-PASS PULMONARY RETENTION OF SUFENTANIL AT 3 DIFFERENT BACKGROUND BLOOD-CONCENTRATIONS OF THE OPIOID

Using a double-indicator technique, we have studied, in 10 patients un dergoing 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 in fusion. Mean first-pass pulmonary retentions at these concentrations w ere 68 (95 % confidence intervals 62-73), 65 (60-70) and 60 (52-67) %, respectively. First-pass pulmonary retention of sufentanil was signif icantly lower at the highest background concentration compared with th e lowest background concentration. First-pass pulmonary retention of s ufentanil was partly saturable in the range of concentrations used for clinical purposes.