Relationship of uric acid concentrations and severe intraventricular hemorrhage/leukomalacia in the premature infant.

The purine metabolite hypoxanthine accumulates with hypoxia ischemia and with reperfusion is converted to uric acid (UA). We hypothesized that elevated UA concentration is a marker of previous hypoxia ischemia and would identify infants at greatest risk for having subsequent intraventricular hemorrhage (IVH)/periventricular leukomalacia (PVL). We determined the relationship between UA concentrations in the first postnatal day and the development of severe IVH, PVL, or both in 58 infants of birth weight 865 +/- 177 gm and gestational age 27 +/- 2 weeks. Severe IVH developed in 10 (17%) infants and PVL in 3 (5.1%) infants. UA concentrations on day 1 (obtained at 16 +/- 4 hours) were 7.9 +/- 2.8 mg/dl and increased to 9.5 +/- 2.58 mg/dl on day 2. UA concentrations on day 1 were higher in infants with severe IVH/PVL versus those in infants with neither condition: 10.2 vs 7.3 mg/dl (p = 0.005). Infants with hyperkalemia on the second postnatal day had higher UA concentrations on the first day versus infants with normal potassium levels: 11.7 +/- 2 mg/dl versus 6.8 +/- 1.8 mg/dl (p < 0.0005). Infants with severe IVH/PVL had higher potassium levels on day 2 versus infants with neither condition: 11.9 vs 6.9 mg/dl (p < 0.048). By univariate analysis UA concentrations were significantly related to gestational age (p = 0.005) and birth weight (p = 0.03). Only UA concentration (p = 0.004) and gestational age (p = 0.02) were related to IVH/PVL. By multivariate analysis UA remained significantly related to IVH/PVL even when adjusted for other clinical variables, with an odds ratio estimate of 1.63 (95% confidence interval 1.16 to 2.31). In conclusion, higher UA concentrations on the first postnatal day were associated with the subsequent development of severe IVH/PVL and with subsequent hyperkalemia. Elevated UA concentrations in the first postnatal day may help to identify a subset of premature infants at greatest risk for having subsequent hemorrhagic ischemic injury.

Apnea after immunization of preterm infants.

OBJECTIVE: To determine the frequency of adverse reactions, particularly the occurrence of apnea, among preterm infants after immunization with diphtheria and tetanus toxoids and whole cell pertussis vaccine adsorbed (DTP) and Haemophilus influenzae type b conjugate (HibC) vaccine in the neonatal intensive care unit. STUDY DESIGN: After the occurrence of apnea in two preterm infants following immunization with DTP and HibC, a prospective surveillance of 97 preterm infants younger than 37 weeks of gestation who were immunized with DTP (94 also received HibC at the same time) in the neonatal intensive care unit was performed to assess the frequency of adverse reactions and in particular, the occurrence of apnea. For each infant, data were recorded for a 3-day period before and after receipt of the immunization. RESULTS: The majority of preterm infants tolerated immunizations with DTP and HibC without ill effects. However, 12 (12%) infants experienced a recurrence of apnea, and 11 (11%) had at least a 50% increase in the number of apneic and bradycardic episodes in the 72 hours after immunization. This occurred primarily among smaller preterm infants who were immunized at a lower weight (p = 0.01), had experienced more severe apnea of prematurity (p = 0.01), and had chronic lung disease (p = 0.03). CONCLUSION: The temporal association observed between immunization of preterm infants and a transient increase or recurrence of apnea after vaccination merits further study. Cardiorespiratory monitoring of these infants after immunization may be advisable.