Improved pulmonary adaptation in newborn calves with postnatal acidosis

The adaptation of newborn calves to extra-uterine life was evaluated by measuring arterial blood gases, acid-base values, blood ions and lung mechanical function parameters in normal and acidotic calves during the first 24 h. Twenty-seven Holstein Friesian newborn calves were divided into two groups according to their immediate post partum arterial blood pH values (Group A blood pH > or = 7.2: normal group; Group B blood pH between 7.2 and 7.0: acidotic group). Pulmonary function parameters were measured and arterial blood samples were analysed for blood gases, acid-base variables and ion content immediately post partum (within 2 min) and then 6 and 24 h after calving. Lung resistance and maximal difference between pressure maximum and pressure minimum (max delta Ppl) decreased, while dynamic lung compliance increased significantly in both groups. Immediately post partum the lung resistance and max delta Ppl were significantly higher in the acidotic group than in the normal group. The arterial blood pH progressively compensated with time in both groups during the first 24 h and there was no difference in arterial blood pH values between the two groups 6 h after birth. These results showed that the compensation of acidosis was associated with the improvement in lung mechanics and these changes occurred mainly during the first 6 h of life. Moderate to pronounced acidosis did not affect the pulmonary adaptation negatively, although some respiratory mechanics parameters (max delta Ppl), blood pH and Ca(2+)ion concentrations remained significantly different between the normal and acidotic groups at 24 h. This might be the result of overcompensation of acidosis and the interdependence between blood pH and Ca(2+)concentrations.