Evaluation of body fluid status after cardiac surgery using bioelectrical impedance analysis

Background. In. the assessment of fluid status after cardiac surgery, we ap plied bioelectrical impedance analysis (BIA) to measure the total body wate r (TBW), extracellular fluid (ECF), and intracellular fluid (ICF), and eval uated its validity. Methods. Thirty patients who underwent cardiopulmonary bypass (CPB group) a nd 19 surgical patients not receiving CPB (non-CPB group). Results. The change of BIA values (Delta TBW, Delta ECF, Delta ICF), body w eight and cumulative fluid balance were determined for 120 postoperative ho urs, and the relationship between BIA values and body weight and fluid bala nce were evaluated. Postoperative changes in BIA values in the CPB group we re compared with those in the non-CPB group. Finally the ECF/ICF ratio and hemodynamic parameters were compared. Delta TBW and Delta ECF correlated wi th changes in body weight and fluid balance, respectively. Especially there was a high correlation in each case although large deviations in the slope of the regression lines were observed TBW and ECF increased from immediate ly after operation up to 96 hours (the maximum value was at day 2). On the other hand, ICF decreased from 48 to 72 hours after operation. There were s ignificant high ECF/ICF in the CPB group compared with the non-CPB group fr om 12 to 72 postoperative hours. We found that ECF/ICF correlated inversely with mean blood pressure, mixed venous oxygen saturation and colloid osmot ic pressure, acid positively with central venous pressure and pulmonary art ery wedge pressure. Conclusions. It was considered that BIA was useful for evaluating the relat ive changes in TBW and fluid distribution, and ECF/ICF might be a new param eter for abnormal water metabolism after cardiac surgery.