The Influence of Ischemia-Reperfusion Injury on Plasma Malondialdehyde in Children Undergoing Cardiopulmonary Bypass

Abstract

Toxic oxygen free radicals (OFRs) are produced after ischemia-reperfusion injury, which can be observed during cardiopulmonary bypass (CPB). In a pilot study conducted in a tertiary care pediatric intensive care unit, we sought to determine plasma malondialdehyde (MDA) levels, a marker of OFR production, in children undergoing CPB, and to relate the findings to gastric intramucosal pH and PCO2 (pHi, PiCO2) and serum lactate. Thirteen nonconsecutive children (age: 56 ± 58 months) were included in the study. After induction of general anesthesia and endotracheal intubation, a tonometer nasogastric tube was positioned in the stomach; gastric pHi and PiCO2, arterial PCO2 (PaCO2), MDA, and lactate were measured 1 hour later (time 0) and 1 to 48 hours after initiation of CPB (times 1, 4, 8, 12, 16, 20, 24, 32, 40, and 48). Data for each variable were compared with baseline values for statistical significance. Free MDA levels increased by more than 50% in 11 patients (85%) and a statistically significant difference was found between the highest and the baseline free MDA concentrations (p < .0025). Low gastric pHi after the first 8 hours post-CPB was significantly associated with a late rise in MDA levels. A stepwise multivariate regression analysis showed that the highest PiCO2:PaCO2 ratio was correlated to the highest MDA level (p < .0001). A low gastric pHi later than 8 hours after CPB or a high PiCO2: PaCO2 ratio, as observed in this study, may indicate secondary splanchnic hypoperfusion with increased OFR production.