[The effect of hemodilution on the indices of aerobic metabolism and water metabolism in children with congenital heart defects operated on under artificial circulation].

The majority of pediatric cardiosurgery centers make use of cardiopulmonary bypass (CPB) with low hematocrit, and therefore we deemed it interesting to investigate the pathological effects of hemodilution on patients. Specifically, we studied the effect of hemodilution on aerobic and water metabolism in children with congenital heart disease subjected to CPB. Two groups of patients were examined. In the studied group (n = 12, mean age 7.1 +/- 1.1 years) the blood-fluid ratio in primary filling of the CPB device was 1:6.2 +/- 0.7 and minimal hematocrit during myocardial ischemia 18 +/- 0.7%. Control group consisted of 7 patients aged 8.3 +/- 0.6 years, with the above values 1:2.8 +/- 0.4 and 22 +/- 1.6%, respectively. The groups were similar as regards the initial status of patients, level of hypothermia, and duration of myocardial ischemia. Gas content in venous blood was the criterion of aerobic metabolism. Fluid accumulation in the extravasal space during and after surgery was assessed by bioelectroimpedance measurements of the total extracellular extravasal fluid (EEF). Monitoring showed a decrease of hematocrit during CPB to 18 +/- 0.7%, saturation of venous blood with oxygen within 70-75%, and oxygen content 37-43 mm Hg. In the main group a manifest increase of EEF was observed as early as during the early postperfusion period; this increase is probably one of the main components in the detrimental effect of hemodilution. Redistribution of fluid after CPB leads to expressed interstitial edemas and impairs the function of vital organs. That is why signs of cardiorespiratory failure were observed in the main group. Thus, one of the main problems in CPB with low hematocrit is fluid accumulation in the extravasal space.