Variations in local PGE levels: a potential factor in therapeutic responsiveness?

It was hypothesized that it is the concentration of PGE in the plasma which actually reaches the ductus arteriosus which determines ductal response to PGE administration. Therefore, site specific PGE levels were studied in two infants with ductus dependent congenital heart lesions who were receiving PGE1 infusions. PGE levels were found to vary in a fashion related to the infusion site and the specific cardiac anatomy and hemodynamics of each patient. One of our patients, for instance, had a double outlet right ventricle with high pulmonary vascular resistance and right to left ductal shunting. This infant was given an intraarterial infusion of PGE. The plasma concentrations of PGE in the ductal blood of the infant were negligible. Assuming that ductal site specific PGE levels are critical in mediating the therapeutic response, hemodynamics and infusion site are factors that should be considered when initiating a PGE infusion, or in evaluating a therapeutic failure of PGE.