Introduction: Although the management of body water balance on cardiac surgery with cardiopulmonary bypass (CPB), especially in children, is essential, little is known how body water composition changes around CPB. We aim to evaluate a change of intracellular (ICW), extracellular (ECW), and total body water composition (TBW) before and after CPB, using bioelectrical impedance analysis (BIA).

Hypothesis: There is a possibility that the fluid distribution and water balance change depends on intraoperative water balance management and age. Then we investigate the impact of (1) intraoperative water balance management and (2) age at operation on changes of body water composition.

Methods: The forty-five children weighing over 5Kg (Age ranges 3mo-11yo) were enrolled to this study. The body water balance was measured at before, at immediately after CPB, at 1 day, and at 2 days, respectively. Each parameter was compared by the factor of intraoperative water balance and that of age at operation.

Results: The minus water balance during CPB results in significant shortage of ICW which not fully recovered by 2 days after CPB (Figure A). Cases >2yo developed a decrease of ICW and ECW 2 days after CPB, while those <2yo increased (Figure B).

Conclusions: The body water composition significantly changes along CPB than expected. Care must be taken to prevent a harmful dehydration by controlling intraoperative water balance management and by age on the basis of BIA.