Cardiopulmonary bypass (CPB) may produce lung injury with decreased PaO2/FiO2 ratio in patients undergoing CABG surgery. We examined PaO2/FiO2 ratio and incidence of PaO2/FiO2 < 300 or 150 to determine the differences in oxygenation with the use of amrinone-dopamine (DP) or isosorbide dinitrate (IDN)-DP in patients undergoing CABG.

Twenty patients undergoing elective CABG were divided into two groups according to drug used on separation from CPB: IDN-DP (Group 1, n = 10) or amrinone-DP (Group 2, n = 10). Anesthesia was induced and maintained with propofol, fentanyl and vecuronium. IDN infusion (1.0microgram/kg/min) was started preoperatively in both groups. Mild hypothermic CPB was applied with a roller pump and nonpulsatile flow maintained a mean arterial pressure of 60-80 mmHg. In Group 2, amrinone was administered (0.75 mg/kg + 10microgram/kg/min) instead of IDN at the time of CPB separation. DP infusion (3microgram/kg/min) was started at a rectal temperature more than 35.5oC and adjusted to maintain acceptable hemodynamics. IDN-DP or amrinone-DP infusion, monitoring and sedation with propofol were continued in the intensive care unit (ICU). PaO2/FiO2 ratio under controlled ventilation with air/O2 mixture (FiO2 0.6) was checked immediately before CPB (pre-CPB), 30 mins (post-CPB30), 60 mins after CPB (post-CPB60) and 30 mins after admission to ICU (ICU30).

There was no significant difference between the groups in the terms of the duration of arotic cross clamp, PaO2/FiO2 at pre-CPB, PaO2/FiO2 at post-CPB60, PaO2/FiO2 at ICU30 or in the incidence of PaO2/FiO2 < 150, PaO2/FiO2 < 300 at ICU30. But there was a significant difference in PaO2/FiO2 post CPB30 (263.3 ± 105.5 in Group 1 vs. 381.7 ± 69.5 in Group 2, P<0.05).

Amrinone-DP provides more favorable oxygenation immediately after CPB in CABG surgery than IDN-DP.