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Effect of ductal patency on organ blood flow and pulmonary function in the preterm baboon with hyaline membrane disease.

OBJECTIVE
To examine the effect of early ductal ligation vs. maintenance of ductal patency on vital organ perfusion and pulmonary function in premature baboons with hyaline membrane disease.


DESIGN
Randomized, controlled interventional study to compare early ligation with formalin infiltration of the ductus arteriosus.


SETTING
Animal care facility at a dedicated research foundation.


SUBJECTS
Eighteen premature baboons delivered by hysterotomy at 140 +/- 2 day gestation.


INTERVENTION
Nine premature baboons underwent formalin infiltration of the ductus arteriosus (group 1), and nine underwent ductal ligation (group 2). Surgical ligation or formalin infiltration was performed at 2 to 4 hrs of age. Animals were maintained on mechanical ventilation and ventilator parameters were adjusted to maintain PaO2 and PaCO2 within the physiologic range.


MAIN OUTCOME MEASURES
Left ventricular output indexed to body weight and vital organ perfusion were measured at 24 hrs of age by the radiolabeled microsphere method. Lung mechanics, including lung wet/dry weight ratio, total lung water, static compliance and functional residual capacity were measured immediately following euthanasia.


RESULTS
Total pulmonary blood flow was significantly lower (p = .0001) in group 2 (mean = 94 mL/min/kg), compared with group 1 (mean = 287 mL/min/kg). Systemic blood flow and effective pulmonary blood flow were higher in group 1 (p = .07). No significant difference between groups in absolute organ blood flow was noted, although flow as a percent of left ventricular index was significantly higher in all organs except the kidney in group 2. There was no difference in arterial blood gas values, parameters of mechanical ventilation, percent lung water, or postmortem measurement of lung mechanics between groups.


CONCLUSION
Early ductal ligation did not result in improved cardiac output, increased organ blood flow, or improved pulmonary function. We postulate that gradual constriction of the ductus arteriosus may play an important role in successful cardiovascular adaptation in the premature infant. While it is clear that premature infants with symptomatic patent ductus arteriosus often benefit from ductal closure, we question the practice of prophylactic early ductal closure.