Increased exhaled carbon monoxide concentration during living donor liver transplantation

Exhaled carbon monoxide concentration (ExCO-C) has been reported to increase in oxidative tissue injuries such as systemic inflammation, and is thought to reflect increased heme breakdown in the affected organ. As a transplanted liver undergoes ischemia-reperfusion, we hypothesized that ExCO-C might also increase following liver transplantation and might serve as a measure of the severity of the graft tissue injury. We prospectively studied 67 living donor liver transplantation (LDLT) patients in a consecutive fashion. During anesthesia, ExCO-C was determined at 6 time points, ranging from anesthesia induction, to admission to the intensive care unit. We also measured two markers of endothelial cellular injury, i.e., serum soluble thrombomodulin (sTM) and intercellular adhesion molecule (ICAM)-1. At 5 min after reperfusion of the grafted liver, ExCO-C markedly increased from 5.69±2.34 ppm at baseline, to 9.79±4.72 ppm (p<0.0001). There was an excellent correlation among an increase in CO concentration, arterial carboxyhemoglobin levels at the time of reperfusion (r²=0.19, p=0.0003), and postoperative total bilirubin levels (day 1, 2, and 3; r 2=0. 102, 0.109 and 0.100; p=0.008, 0.007 and 0.010, respectively). Serum sTM and ICAM-1 levels were also significantly increased after reperfusion (sTM: 3.3±0.8 to 5.1±1.7 FU/ml, p=0.0001; ICAM-1: 271.9±86.3 to 515.0±157.8 FU/ml, p=0.0001). ExCO-C had a positive relationship with sTM (r2=0.16, p=0.035) and ICAM-1 (e=0.12, p=0.08). There was, however, no correlation of ExCO-C with serum AST/ALT levels or clinical outcomes. This study demonstrated that ExCO-C significantly increased after reperfusion during LDLT. The increased ExCO-C may likely reflect increased heme breakdown and endothelial cell injury in the grafted liver.