[Effectiveness of continuous pulmonary perfusion during total cardiopulmonary bypass to prevent lung reperfusion injury].

The oxygen free radicals and the interaction between neutrophils and endothelium have been implicated in the pathogenesis of lung injury associated with cardiopulmonary bypass (CPB), and in the setting of total CPB, the ischemia-reperfusion injury has been suspected as the mechanism of lung injury. To prevent this reperfusion induced lung injury, we performed continuous pulmonary perfusion during total CPB. We studied 26 infants less than 1 year of age who underwent patch closure of ventricular septal defect. Intermittent mechanical ventilation (5/min) and continuous perfusion of pulmonary artery (30 ml/kg/min) were performed during total CPB in 7 infants (Group P). Whereas 19 infants underwent ordinary CPB (Group N). PaO2/FiO2 ratio was employed for the predictor of lung injury and was calculated before and after CPB. PaO2/FiO2 ratio decreased from 3 to 12 hours after CPB and then increased by 24 hours after CPB in both groups. The lowest PaO2/FiO2 ratio measured at 12 hours after CPB correlated with age and body weight at operation (Spearman's correlation coefficient, 0.59; p = 0.01 and 0.61; p = 0.009, respectively) and strongly correlated with preoperative Rp/Rs ratio (-0.73; p = 0.003). PaO2/FiO2 ratio, however, did not correlate with duration of CPB and aortic cross clamping, preoperative Pp/Ps and Qp/Qs ratio in group N. PaO2/FiO2 ratio of group P at 3, 6, and 12 hours after CPB were higher than those of group N, although there were no significant difference When analysis was made on the infants with high pulmonary vascular resistance (preoperative Rp/Rs ratio > or = 0.1), PaO2/FiO2 ratio of group P (n = 6) at 3, 6 and 12 hours after CPB were higher than those of group N (n = 11), and the difference was statistically significant at 12 hours after CPB (291.1 +/- 15.5 versus 199.6 +/- 27.0, p = 0.027. These results implicate that young age, low body weight and especially high pulmonary vascular resistance were incremental risk factor of lung injury after CPB and, furthermore, ischemia reperfusion injury can be the initiating factor of lung injury. The results also suggest that continuous pulmonary perfusion during total CPB is an effective mean to prevent lung injury particularly for the infants with high pulmonary vascular resistance.