Catecholamine surge and lung function after delivery.
Lung function was measured at 30 minutes and again at 2 hours after birth in 12 infants delivered vaginally, in 15 infants delivered by elective caesarean section under general anaesthesia (GA), and in 15 delivered under epidural anesthesia (EDA). Umbilical arterial blood was analysed for pH and for concentrations of catecholamines and cortisol. No important differences in gestational age, birthweight, Apgar scores, or haematocrit were found among the three groups. Tidal volume and minute ventilation measured 30 minutes after birth were lower in infants delivered by caesarean section than in those delivered vaginally and at 2 hours the tidal volume was still lower in the babies delivered by caesarean section than in those delivered vaginally. Dynamic compliance was lower at 30 minutes in the group that had a caesarean section than in the vaginal group, and this difference was significant at two hours. Tidal volume, minute ventilation, and dynamic compliance in the GA and EDA groups did not differ. The catecholamine and cortisol concentrations at birth were higher in the vaginal group than in the group delivered by caesarean section. Two hours after birth there was a significant correlation (r = 0.84) between the catecholamine concentrations of the infants born vaginally and lung compliance. The lower dynamic lung compliance in infants delivered by elective caesarean section might be explained by delayed absorption of liquid in the lung due to lack of catecholamine surge.