Background—Cardiac troponin-T is a sensitive marker of myocardial damage. In a prospective study, the effect of 2 different pH strategies during cardiopulmonary bypass on ischemic myocardial injury and clinical outcome was measured in a pediatric population.Methods and Results—One hundred one patients (31 neonates 13.2±8.3 days and 70 children 34.5±44.1 months of age) undergoing open-heart surgery were selected to either &agr;-stat (n=51) or pH-stat (n=50) acid-based management protocol. Serum troponin-T levels were measured before and 30 minutes after bypass and then 4 and 24 hours postoperatively. Surgical procedure, bypass details, inotropic support requirement, and postoperative recovery were recorded. Baseline troponin-T level was higher in neonates than in children (0.18±0.22 versus 0.04±0.05 &mgr;g/L,P=0.02). Also, a higher baseline level was found in patients with pulmonary hypertension (0.13±0.21 versus 0.04±0.05 &mgr;g/L,P=0.04). Cyanotic children showed a higher peak troponin-T level (3.76±3.11 versus 1.67±1.33 &mgr;g/L,P=0.04). Peak troponin levels showed a correlation with the length of circulatory arrest and aortic cross-clamp time. Postoperative levels remained high at 24 hours in patients requiring inotropic support. Peak troponin-T levels were significantly lower in the pH-stat group in patients with pulmonary hypertension (P=0.03) and in cases where circulatory arrest (P=0.01) or inotropic support (P=0.01) was necessary during operation than in those with &agr;-stat technique. Postoperative ventilation time and length of intensive care unit stay were also significantly longer with &agr;-stat than with pH-stat technique (P=0.005 andP=0.006, respectively).Conclusions—Cardiac troponin-T sensitively reflects myocardial damage in children. Our results suggest that pH-stat acid-based management protocol may provide better protection against ischemic myocardial damage than &agr;-stat technique.