The influence of crying on the ductus arteriosus shunt and left ventricular output at birth.

BACKGROUND

During neonatal transition, ductus arteriosus (DA) flow changes from right-to-left to left-to-right and contributes considerably to the increase in pulmonary blood flow. Large transpulmonary pressures generated by crying at birth can influence the DA shunt.

OBJECTIVE

This study aimed to assess differences in DA shunt during quiet breathing and crying directly after birth.

METHODS

In healthy term infants born by caesarean section, echocardiography was performed at 2, 5 and 10 min after birth. The velocity time integral of DA flow, DA flow ratio (right-to-left/left-to-right flow) and left ventricular output were assessed using echocardiography. Shunting was compared within each patient during crying and quiet breathing, and between time points.

RESULTS

A total of 23 infants were studied. The velocity time integral of left-to-right shunting was significantly larger during the inspiratory phase of crying than during quiet breathing [12.8 (9.2-17.4) vs. 5.9 (3.9-7.7) cm at 2 min, p < 0.0001; 14.3 (11.5-22.3) vs. 6.7 (4.1-11.1) cm at 5 min, p < 0.0001, and 18.6 (14.8-22.5) vs. 6.7 (4.4-10.7) cm at 10 min, p < 0.0001, after birth]. The increase in left-to-right shunting during crying was independent from the cardiac cycle as the QRS start of shunt interval time was 138 (82) ms during crying and 156 (35) ms during quiet breathing (n.s.). The DA flow ratio was lower in infants who cried at 0-1 time points versus those who cried at 2-3 time points (n.s.) out of the 3 time points measured. Left ventricular output was higher in infants who cried at 2-3 time points versus 0-1 time points (n.s.).

CONCLUSION

Crying at birth significantly influences the DA shunt during transition.