Low cardiac output can be encountered after corrective surgery for complex congenital malformation in children and infants and is often accompanied by an impairment of renal function, ascites, hyperosmolarity and hyperpyrexia. In most instances, combined afterload-reduction and inotropic stimulation will be effective. If low cardiac output persists, a peritonealdialysis (PD) may allow correction of fluid balance and consecutive improvement of hemodynamics. During a 18 month-period, PD was performed in 14 children in the postoperative period following major cardiac surgery (transposition 5, Fallot tetralogy 5, various complex anomalies 4). This represents 3.1% of all cardiac operations performed in children with congenital heart disease throughout the same period. There were 8 males and 6 females with a median age of 2.5 years (range 3 days to 4 years) and a median bodyweight of 5.5 kg (range 3.4 to 10 kg). Low cardiac output was defined when two or more of the following factors were met: mean arterial pressure (MAP) below 40 mm Hg despite inotropic stimulation, central venous pressure (CVP) over 15 mm Hg, urine production less than 1 ml/kg/hour and/or increasing transaminases. Before starting peritoneal dialysis all children received combined positive inotropic and vasodilative therapy. The PD-catheter was introduced 8 to 30 hours after operation. We used a PD-solution with 1.5% and/or 4.5% glucose. Fluid balance was monitored hourly. Just after introduction of the catheter a mean of 65 ml +/- 25 ml/kg ascites could be removed and the total quantity of removed fluid was 175 ml +/- 45 ml/kg bodyweight.(ABSTRACT TRUNCATED AT 250 WORDS)