A Ratio of Arterial Oxygen Tension to Inspired Oxygen Fraction (PaO2/FiO2 ratio) after Cardiopulmonary Bypass in Coronary Artery Bypass Graft Surgery: Amrinone-Dopamine versus Isosorbide Dinitrate-Dopamine

Abstract

Background: Cardiopulmonary bypass (CPB) may produce lung injury with decreased PaO/FiO ratio in patients undergoing CABG surgery. We examined PaO/FiO ratio and incidence of PaO/FiO ＜ 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. Methods: 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 (1.0g/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 + 10g/kg/min) instead of IDN at the time of CPB separation. DP infusion (3g/kg/min) was started at a rectal temperature more than 35.5 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). PaO/FiO ratio under controlled ventilation with air/O mixture (FiO 0.6) was checked immediately before CPB (pre-CPB), 30 mins (post-CPB), 60 mins after CPB (post-CPB) and 30 mins after admission to ICU (ICU). Results: There was no significant difference between the groups in the terms of the duration of arotic cross clamp, PaO/FiO at pre-CPB, PaO/FiO at post-CPB, PaO/FiO at ICU or in the incidence of PaO/FiO ＜ 150, PaO/FiO ＜ 300 at ICU. But there was a significant difference in PaO/FiO post CPB (263.3 105.5 in Group 1 vs. 381.7 69.5 in Group 2, P ＜ 0.05). Conclusions: Amrinone-DP provides more favorable oxygenation immediately after CPB in CABG surgery than IDN-DP.