[Lactate dehydrogenase isoenzymes in the serum and bronchial aspirate of newborn infants with respiratory difficulty of different etiologies].

Objective: To study the usefulness of lactate dehydrogenase isoenzymes serum determination as tissue injury markers in newborns with respiratory distress.

Design And Methods: Ninety four neonates were studied and classified in two groups: 64 suffering various types of respiratory problems, and 30 healthy newborns of a similar birth weight and gestational age. LDH activity and its isoenzymes was determined in the serum of all the infants and in 23 samples of the bronchial aspirate of infants who required ventilation support. The isoenzymes were separated by electrophoresis on agarose gel and their activity was expressed as percentage of the total LDH.

Results: LDH1 and LDH2 isoenzymes were decreased, and LDH4 and LDH5 isoenzymes were significantly increased (p > 0.001) in infants serum with respiratory distress, compared with controls. We compared LDH isoenzymes values found in bronchial aspirate with their values found in serum of ventilate infants, and we found a significant levels of LDH2 and LDH3 were lower, and those of LDH5 were higher (p < 0.001) in bronchial aspirate than in serum and a positive correlation (r = 0.47, p < 0.01) between LDH5 values in both samples.

Conclusions: The study shows significantly differences in the LDH isoenzyme profiles of neonates with respiratory distress compared with controls. The increase in serum of LDH4 and particularly of LDH5 isoenzymes could be an effective marker of tissue damage in lung disease in the newborn.