CONCENTRATION-RESPONSE RELATIONSHIPS FOR FENTANYL AND SUFENTANIL IN PATIENTS UNDERGOING CORONARY-ARTERY BYPASS-GRAFTING

Background: Concentration-response relationships for sufentanil and fe ntanyl are undefined in patients undergoing coronary artery bypass gra fting. Methods: Separate studies of sufentanil and fentanyl were perfo rmed in lorazepam-premedicated patients undergoing coronary artery byp ass grafting, patients were assigned randomly to groups with different prebypass effect-site opioid concentrations targeted by computer-assi sted infusion. The target sufentanil concentrations were 0.4 ng/ml (gr oup L-S, n = 11), 0.8 ng/ml (group M-S, n = 10), and 1.2 ng/ml (group H-S, n = 11); the target fentanyl concentrations were 5 ng/ml (group L -F, n = 7), 10 ng/ml (group M-F, n = 7), and 15 ng/ml (group H-F, n = 6). propofol at a dose of 1 mg/kg was administered at induction of ane sthesia and isoflurane was used for hemodynamic control. Hemodynamics, end-tidal isoflurane concentration, and opioid concentration in arter ial blood were measured at specific intervals. Results: Intraoperative opioid concentrations were constant, averaging 0.71 +/- 0.13, 1.25 +/ - 0.21, and 2.03 +/- 0.46 ng/ml for groups L-S, M-S, and H-S, respecti vely, and 7.3 +/- 1.1, 13.2 +/- 2.2, and 24.4 +/- 5.8 ng/ml for groups L-F, M-F, and H-F, respectively (all mean +/- SD). Isoflurane require ments were significantly greater in group L-S than in groups M-S and H -S and greater in group L-F than in groups M-F and H-F. The serum opio id and end-tidal isoflurane concentrations were correlated significant ly. There were no intergroup differences in hemodynamics. Conclusions: Serum sufentanil and fentanyl concentrations of 0.71 +/- 0.13 ng/ml a nd 7.3 +/- 1.3 ng/ml, respectively, are on the steep parts of the conc entration-response relationships and facilitate prebypass hemodynamic control in patients undergoing coronary artery bypass grafting with op ioid-isoflurane anesthesia. Concentrations of sufentanil greater than or equal to 1.25 + 0.21 ng/ml and of fentanyl greater than or equal to 13.3 +/- 2.2 ng/ml minimize isoflurane requirements but do not improv e hemodynamic control.