Oxidative stress seems to contribute to
cardiopulmonary bypass (CPB)-related postoperative complications. Pediatric patients are particularly prone to these complications. With this in mind, we measured oxidative stress markers in blood plasma of 20 children undergoing elective heart surgery before, during, and up to 48 h after cessation of CPB, along with inflammatory parameters and full analysis of
iron status. Ascorbate levels were decreased by approximately 50% (P < 0.001) at the time of aorta cross-clamp removal (or pump switch-off in 4 patients with partial CPB), and associated with corresponding increases in dehydroascorbate (P < 0.001, r = -0.80) and
malondialdehyde (P < 0.01, r = -0.59). In contrast to the immediate oxidative response, peak levels of
IL-6 and
IL-8 were not observed until 3-12 h after CPB cessation. The early loss of ascorbate correlated with duration of CPB (P < 0.002, r = 0.72), plasma
hemoglobin after cross-clamp removal (P < 0.001, r = 0.70), and
IL-6 and
IL-8 levels at 24 and 48 h after CPB (P < 0.01), but not with postoperative
lactate levels, strongly suggesting that
hemolysis, and not
inflammation or
ischemia, was the main cause of early oxidative stress. The correlation of ventilation time with early changes in ascorbate (P < 0.02, r = 0.55), plasma
hemoglobin (P < 0.01, r = 0.60), and
malondialdehyde (P < 0.02, r = 0.54) suggests that
hemolysis-induced oxidative stress may be an underlying cause of CPB-associated pulmonary dysfunction. Optimization of
surgical procedures or therapeutic intervention that minimize
hemolysis (e.g., off-pump surgery) or the resultant oxidative stress (e.g.,
antioxidant treatment) should be considered as possible strategies to lower the rate of postoperative complications in pediatric CPB.