Low platelet count not associated with patent ductus arteriosus

By MedWire Reporters

Thrombocytopenia in the first 24 hours after birth is not linked to patent ductus arteriosus (PDA) in low birthweight infants, research shows.

The results, from a large retrospective analysis conducted at two centers treating very low birthweight/extremely low birthweight (VLBW/ELBW) infants, showed no association between platelet count and a higher incidence of PDA.

In contrast, sepsis and a lower gestational age or birthweight were independent risk factors for DA patency. "Interestingly, all the latter variables may affect platelet function," report Hannes Sallmon (University Medical Center, Berlin, Germany) and colleagues in the journal Pediatrics.

PDA affects approximately 60% of preterm infants born before 28 weeks' gestation. DA closure occurs in the first 3 days after birth when oxygen tension increases to promote initial ductal constriction. Declining levels of prostaglandin E2 also promote DA closure.

Recently, some experimental studies have suggested that platelet-triggered ductal sealing is involved in definite DA closure. Findings on the relationship between platelet count and PDA frequency are mixed and controversial, however.

In the present study, Sallmon and colleagues conducted a retrospective analysis of 1350 VLBW (<1500 g) infants, including 592 EBLW (<1000 g) infants.

Platelet counts did not differ between VLBW infants with and without PDA. Platelet counts below 150,000/µL, which met the definition for thrombocytopenia, were recorded in 16.8% of VLBW infants with PDA and in 15.9% of infants without PDA.

Similarly, 19.3% of ELBW infants with PDA had platelet counts below 150,000/µL compared with 21.1% of ELBW infants without PDA.

Among the 222 VLBW infants with thrombocytopenia in the first 24 postnatal hours, 57.7% had PDA compared with 56.0% of the 1128 infants without thrombocytopenia who had PDA. This difference was not statistically significant.

In addition, the researchers noted that neither mild (<150 000 /µL), moderate (<100 000 /µL), nor severe (<50 000 /µL) thrombocytopenia in the first 24 hours was associated with a higher incidence of PDA in any of the low birthweight infants.

Low platelet counts were also not related to a failure of pharmacologic PDA treatment or the need for surgical ligation.

The researchers speculate that platelet dysfunction caused by immaturity or critical illness, rather than platelet number contributes to the pathogenesis of PDA. The rate of PDA on days 4-5 was significantly higher in the ELBW patients compared with the VLBW patients, they note.

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