Circulating neutrophil concentration and respiratory distress in premature infants

Abstract

Background: The acute disappearance of neutrophils from the circulation can be associated with pulmonary leukostasis, lung injury, and respiratory distress.

Objective: To determine whether a low concentration of mature neutrophils in the peripheral blood soon after birth is associated with an increase in subsequent respiratory distress in premature infants.

Design: A cohort study performed by chart review at a tertiary medical center.

Subjects: Premature infants (birth weight 500 to 1250 g) who had a complete blood count obtained within 2 hours of delivery (n = 237). Patients in the lowest quartile of mature neutrophil concentrations (early neutropenia, < or =0.90 x 10(9) neutrophils/L blood) were compared with patients in the remaining 3 quartiles (control group).

Results: Low neutrophil concentrations were transient in the early neutropenia group. The concentration of mature circulating neutrophils rose from 0.49 +/- 0.25 x 10(9) cells/L at an average of 1 hour after delivery to 2.8 +/- 2.2 x 10(9) cells/L within 6 to 8 hours in the early neutropenia group and from 4.6 +/- 4.8 x 10(9) cells/L to 8.2 +/- 8. 0 x 10(9) cells/L in the control group during the same time period. Respiratory support immediately after birth was similar in both groups of infants, but by 12 hours patients who had early neutropenia required significantly greater inflation pressures and concentrations of inspired oxygen. By 1 week after birth patients who had early neutropenia were more likely to require mechanical ventilation and supplemental oxygen. Pulmonary interstitial emphysema, serious intraventricular hemorrhage, and chronic lung disease occurred more frequently in patients with early neutropenia.

Conclusion: A low concentration of mature neutrophils in the systemic circulation of premature infants within 2 hours of birth is associated with more severe respiratory distress during the first postnatal week and with an increased risk of serious complications of prematurity.