The cardiovascular changes following portosystemic shunt surgery (PSSS) in 33 children with extrahepatic portal hypertension (EPH) were studied to determine if portosystemic shunt surgery had any influence on the cardiovascular state. Haemodynamic data were obtained using two-dimensional and M-mode echocardiography, pulsed-wave Doppler and direct invasive techniques. Postoperatively all patients developed a hyperdynamic state, associated with an increase in cardiac index (CI), heart rate (HR) and a decrease in systemic vascular resistance index (SVRI). In 16 patients (group I), who preoperatively exhibited a hyperdynamic state accompanied by pulmonary hypertension, postoperative studies found an increase in acceleration time to ejection time ratio (AT/ET) in the pulmonary artery from 0.32 +/- 0.05 (mean +/- SEM) to 0.43 +/- 0.01; P < 0.01. Nine patients (group II) who were normodynamic preoperatively developed pulmonary hypertension and right ventricular (RV) dysfunction postoperatively: decrease in AT/ET from 0.42 +/- 0.02 (mean +/- SEM) to 0.32 +/- 0.01; P < 0.01 and an increase in maximal peak pulmonary artery velocity to acceleration time ratio (Vmax/AT) from 702.56 +/- 69.10 (mean +/- SEM) to 1127 +/- 105.30 cm.sec-2; P < 0.01. In eight patients (group III) who were normodynamic preoperatively and were treated with dobutamine infusions at a rate of 5 micrograms.kg-1.min-1 postoperatively, the CI was found to increase from 5.28 +/- 1.1 (mean +/- SEM) to 7.97 +/- 1.64 L.min-1.m-2; P < 0.01, left ventricular ejection fraction (LVEF) from 69.0 +/- 4.1 (mean +/- SEM) to 81.0 +/- 2.9%; P < 0.01 and AT/ET from 0.37 +/- 0.04 (mean +/- SEM) to 0.44 +/- 0.03; P < 0.01.(ABSTRACT TRUNCATED AT 250 WORDS)