Objective: This prospective study examined purine metabolism in relation to free oxygen radical activity, as reflected by lipid peroxide levels in umbilical cord blood at birth.
Setting: Departments of Obstetrics and Gynaecology and of Chemical Pathology, the Chinese University of Hong Kong, Hong Kong, and Purine Research Laboratory, UMDS of Guy's and St. Thomas' Hospitals, London, UK.
Methods: Umbilical cord arterial and venous blood samples were collected from 132 singleton term deliveries for determination of hypoxanthine, xanthine, inosine, uric acid, organic hydroperoxides (OHP) and malondialdehyde. Oxygen saturation, PO2, pCO2, pH, and base excess (BE) were also measured.
Results: There was a significant correlation between umbilical arterial and venous levels of hypoxanthine, xanthine, inosine, uric acid and all acid-base parameters (p < 0.001). Significant arteriovenous differences were observed for all parameters with the exception of inosine, uric acid and OHP. Umbilical arterial xanthine and potassium correlated significantly with OHP, but hypoxanthine, inosine and uric acid did not. In 13 babies classified as severely asphyxiated at birth (umbilical arterial pH <7.15, BE <-8), xanthine and OHP levels were significantly elevated when compared with non-asphyxiated babies. No significant differences were observed for hypoxanthine, inosine or uric acid.
Conclusion: The findings indicate that OHP, either in cord arterial or venous blood, is the best marker of free oxygen radical activity in the fetus, and that this correlates with other evidence of cellular hypoxia-reperfusion injury. We propose OHP is a better measure of perinatal outcome than either acid-base balance or hypoxanthine.