Abstract
Reopening of the ductus arteriosus after INDO closure is now the major problem with INDO treatment. Among 148 infants treated with INDO, 91% responded by closing their ductus after INDO. However, 27% of the responders subsequently reopened their ductus (<1000g=33%, >1500g=12%). 70% of the infants, who were retreated with INDO after reopening of their ductus, were still responsive to INDO and closed their ductus again. In full-term lambs (150d), the ability of the ductus to relax or contract depends on the amount of Lt→Rt shunt (shunt) through its lumen. To see if ductus constriction in preterm lambs caused this same loss of ductus responsiveness, we used 42 lambs (delivered by C-section at 120-147d, and ventilated 6.6±0.5 hr) and measured ductus resistance and shunt by microspheres. 25 lambs had "moderate" ductus constriction (shunt >10% C.O. [40±5%]); 17 had "tight" constriction (shunt <10% C.O.). Following hemodynamic measurements the ductus was studied in vitro. Ductuses ≥135d, that were "tightly" constricted before sacrifice, had a significantly diminished ability to contract (to O2+INDO) and relax (to PGE2) compared to "moderately" constricted ductuses ≥135d. However, "tightly" constricted ductuses ≤134d: 1) had the same ability to relax to PGE2 as "moderately" constricted ductuses, and 2) had twice the contracting ability as "tightly" constricted ductuses ≥135d. This persistence of responsiveness, following ductus constriction in immature lambs, may account for the high reopening rate after closure in preterm infants.
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Clyman, R., Campbell, D. & Heymann, M. REOPENING OF THE DUCTUS ARTERIOSUS AFTER INDOMETHACIN (INDO) CLOSURE. Pediatr Res 18 (Suppl 4), 1330 (1984). https://doi.org/10.1203/00006450-198404001-01332
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DOI: https://doi.org/10.1203/00006450-198404001-01332