Abstract
The effect of indomethacin treatment of patent ductus arteriosus (PDA) on blood pressure was studied in 24 preterm infants. PDA was diagnosed clinically and confirmed by echocardiography; the effect of treatment was monitored echocardiographically. Hourly intra-arterial recordings of systolic, diastolic, and mean blood pressure were averaged for the 48 hours before the first dose of indomethacin and for each of the three 24 hour periods after the first dose. In the 16 infants in whom treatment was successful, the average mean blood pressure increased significantly over the three days after the first dose. On the third day after beginning treatment with indomethacin the average increase in mean blood pressure was 10.4 mm Hg. Fourteen of 16 infants showed an increase of 4 mm Hg or more. Systolic and diastolic blood pressure increased significantly by similar amounts, so the pulse pressure did not change. In the eight infants treated unsuccessfully, there was no consistent change in any of the blood pressure parameters. The maximum increase in mean blood pressure was 3 mm Hg. These findings confirm that PDA is one of the determinants of blood pressure in preterm infants. The effect is general and there is no consistent change in pulse pressure when a PDA is closed. A general increase in blood pressure is a useful additional indicator of successful medical ductal closure.