['The hypotheses were that glucocorticoid administration could improve ventricular recovery by reducing cardiopulmonary bypass (CPB)-induced inflammatory response and that presurgical administration might be more effective than intraoperative dosing.', 'Animal case study.', 'Crossbred piglets (5-7 kg).', 'Piglets were cooled with CPB, followed by 120 mins of deep hypothermic circulatory arrest (DHCA). Animals were rewarmed to 38 degrees C, removed from CPB, and maintained for 120 mins. Methylprednisolone (60 mg/kg) was administered in the CPB pump prime (intraoperative glucocorticoid [intraop GC]) or 6 hrs before CPB (30 mg/kg) in addition to the intraoperative dose (30 mg/kg; pre- and intraop GC). Controls (no GC) received saline.', 'In no GC, left ventricle (LV) positive change in pressure in time (+dP/dt) (mm Hg/sec) had a mean +/- SD of 1555 +/- 194 at baseline vs. 958 +/- 463 at 120 mins after CPB, p=.01). LV +dP/dt was maintained in glucocorticoid-treated animals (1262 +/- 229 at baseline vs. 1212 +/- 386 in intraop GC and 1471 +/- 118 vs. 1393 +/- 374 in pre-intraop GC). Glucocorticoids reduced myocardial interleukin-6 messenger RNA expression, measured by ribonuclease protection assay, at 120 mins after CPB compared with animals receiving saline (p<.05), although interleukin-6 plasma and LV protein concentrations were not affected. Interleukin-10 myocardial protein concentrations were elevated after CPB-DHCA with higher concentrations in glucocorticoid-treated animals (p<.05). Glucocorticoid treatment maintained myocardial concentrations of the inhibitor of nuclear factor-kappaB in the cytosol and decreased nuclear factor-kappaB concentrations detected in the nucleus in a DNA/protein interaction array.'] Do glucocorticoids reduce cardiac dysfunction after cardiopulmonary bypass and circulatory arrest in neonatal piglets?