The concentration of hypoxanthine and lactate in the blood of healthy and hypoxic newborns

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Abstract
This work examines the correlation between the concentration of hypoxanthine and lactate, the clinical course, and the parameters of the acid-base metabolism in newborns. In order to obtain normal values in mature, healthy newborns (group A)136 determinations of hypoxanthine and 126 determinations of lactate in blood were performed in the first 5 postnatal days. In well prematures (group B) hypoxanthine was determined 18 times and lactate 16 times. In newborns requiring oxygen therapy including ventilator support (group C) hypoxanthine and lactate were determined 36 and 31 times respectively. Hypoxanthine levels in the blood of mature healthy newborns decreased with increasing age. A similar course is known for lactate levels. In the group of well prematures (group B), hypoxanthine and lactate levels have an age dependent course similar to that in group A. Correlations between hypoxanthine and lactate concentrations were observed in all 3 groups but were not noted to be as well defined as has been seen experimentally (e.g. by Saugstad) and thus confirm other clinical results. Among the newborns requiring oxygen therapy (group C) 7 of 36 hypoxanthine values were more than 2 standard deviations above those in the normal group. For lactate group C infants were in 12 of 31 cases above the 2 standard derivation range. The hypoxanthine and lactate concentrations of group C newborns were correlated with clinical and biochemical indicators of hypoxia. Infants with unequivocal signs of hypoxia showed elevated as well as normal hypoxanthine and lactate levels. Conversely, infants without clinical, pathological or biochemical hypoxia indicators showed in some cases elevated hypoxanthine and lactate values. On the whole, lactate levels appear to be a somewhat more sensitive indicator for hypoxia than the hypoxanthine concentration. This corresponds with the theoretical model that during hypoxia the decay of ATP may initially be inhibited by increased glycolysis. Hypoxanthine and lactate levels in the blood of oxygen treated newborns did not correlate statistically to any of the parameters of the acid-base metabolism (pH, pO2, base deficit, O2 saturation). This included patients with predominantly mild to moderate degrees of hypoxia. Evidently, the cellular oxygen deficiency in these children was not marked enough to trigger sufficient severe disturbances in cellular energy stores to cause unequivocal changesin lactate and hypoxanthine concentrations in the blood. Neither hypoxanthine nor lactate determinations are suitable to recognize and quantify hypoxic conditions in the first week of life.