Platelet-Neutrophil Interactions Are Lower in Cord Blood of Premature Newborns

OBJECTIVE

To quantify platelet-neutrophil interaction by flow cytometry, in newborn cord blood, as a function of gestational age.

RATIONALE

Little is known about platelet function markers in the newborn, and developmental variations in these markers are not well described.

METHODS

Cord blood samples were obtained from 64 newborns between 23 and 40 weeks' gestation. The neonates were grouped into three categories: preterm (< 34 weeks' gestation, n = 21), late preterm (34 to < 37 weeks' gestation, n = 22), and term (≥37 weeks' gestation, n = 21). We monitored the expression of P-selectin and the formation of platelet-neutrophil aggregates (PNAs) by flow cytometry while using adenosine 5'-diphosphate (ADP) or thrombin receptor-activating peptide (TRAP) as agonists.

RESULTS

PNAs were significantly lower in preterm compared to term neonates after TRAP or ADP stimulations (11.5 ± 5.2% vs. 19.9 ± 9.1%, p < 0.001, or 24.0 ± 10.1% vs. 39.1 ± 18.2%, p = 0.008, respectively). The expression of P-selectin also tended to be lower in preterm neonates, with significant positive correlations between P-selectin expression and PNA formation.

CONCLUSIONS

The potential formation of PNAs correlates with gestational age. This suggests that the development of functional competencies of platelets and neutrophils continues throughout gestation, progressively enabling interactions between them.

Urinary Allantoin Is Elevated in Severe Intraventricular Hemorrhage in the Preterm Newborn

Germinal matrix intraventricular hemorrhage (IVH) is the most common type of intracranial hemorrhage observed in preterm neonates. It is a precursor of poor neurocognitive development, cerebral palsy, and death. The pathophysiology is not well defined, but damage to the fragile germinal matrix vasculature may be due to free radicals generated during inflammation and as a consequence of ischemia followed by reperfusion. Assessment of the oxidative stress status in these infants is therefore important. Urinary allantoin concentration was measured in preterm neonates as a marker of oxidative stress associated with IVH. Urine was collected from 44 preterm neonates at four time points between 24 and 72 hours of life (HOL), and the allantoin content was determined by gas chromatography mass spectrometry (GCMS). Records were retrospectively reviewed, and the incidence and severity of IVH was categorized as follows: no IVH (n = 24), mild (grade 1-2) IVH (n = 13), and severe (grade 3-4) IVH (n = 7). Neonates with severe IVH showed significantly elevated allantoin levels vs subjects with no IVH from 36 HOL (0.098 ± 0.013 μmol and 0.043 ± 0.007 μmol, respectively, p = 0.002). The allantoin concentration remained elevated even at 72 HOL (0.079 ± 0.014 μmol and 0.033 ± 0.008 μmol, respectively, p = 0.021). There were no significant differences in allantoin levels in the no IVH and mild IVH groups. IVH was diagnosed by head imaging on average at about 11th postnatal day. Urinary allantoin levels were significantly elevated during the first 3 days of life in the neonates subsequently diagnosed with severe IVH, suggesting that oxidative stress might be a crucial factor in IVH pathogenesis. Further studies are needed to assess the usefulness of urinary allantoin in early identification of preterm infants at risk for or with severe IVH and monitoring of the response to interventions designed to prevent or treat it.

Urinary Hypoxanthine as a Measure of Increased ATP Utilization in Late Preterm Infants

OBJECTIVE

To examine the effect of neonatal morbidity on ATP breakdown in late preterm infants.

STUDY DESIGN

Urinary hypoxanthine concentration, a marker of ATP breakdown, was measured from 82 late preterm infants on days of life (DOL) 3 to 6 using high-performance liquid chromatography. Infants were grouped according to the following diagnoses: poor nippling alone (n = 8), poor nippling plus hyperbilirubinemia (n = 21), poor nippling plus early respiratory disease (n = 26), and respiratory disease alone (n = 27).

RESULTS

Neonates with respiratory disease alone had significantly higher urinary hypoxanthine over DOL 3 to 6 when compared with neonates with poor nippling (P = .020), poor nippling plus hyperbilirubinemia (P < .001), and poor nippling plus early respiratory disease (P = .017). Neonates with poor nippling who received respiratory support for 2 to 3 days had significantly higher hypoxanthine compared with infants who received respiratory support for 1 day (P = .017) or no days (P = .007).

CONCLUSIONS

These findings suggest that respiratory disorders significantly increase ATP degradation in late premature infants.