Zinc protoporphyrin-to-heme ratios in high-risk and preterm infants.

OBJECTIVES: To refine the reference range for the zinc protoporphyrin-to-heme ratio (ZnPP/H) of preterm infants, we assessed the impact of maternal risk factors on ZnPP/H and evaluated the impact of changes in iron supplementation on iron status. STUDY DESIGN: The reference range for neonatal ZnPP/H was refined using prospective data from 31 reference infants ≤ 35 weeks' postmenstrual age (PMA) plus retrospective data from 51 infants <30 weeks' PMA, and 59 infants 30-40 weeks' PMA. Cord blood and first week of life values were compared when both were available. The impact of maternal risk factors was assessed by examining prospectively collected ZnPP/H from 48 high-risk infants. The effect of changing iron supplementation guidelines was evaluated by retrospective chart review of serial ZnPP/H from 194 infants. RESULTS: Cord ZnPP/H was lower at 30-35 weeks' gestation than at 24-26 weeks' gestation (P = .01). Cord ZnPP/H values from insulin-dependent diabetic mothers were elevated compared with reference values. Changing the iron supplementation protocol was not associated with improved ZnPP/H measurements. CONCLUSIONS: Cord blood and postnatal reference ranges for ZnPP/H are defined. Iron balance depends on a complex interaction of prenatal and postnatal factors.

Low plasma retinol concentrations increase the risk of developing bronchopulmonary dysplasia and long-term respiratory disability in very-low-birth-weight infants.

BACKGROUND: The effect of inadequate vitamin A during the neonatal period on lung status is still unknown. OBJECTIVE: We tested the hypothesis that low plasma retinol concentrations during the first month of life are independently associated with bronchopulmonary dysplasia (BPD) and long-term respiratory morbidity at 6 mo gestationally corrected age (ie, the age the infant would be had the pregnancy gone to term). DESIGN: Respiratory outcome information was obtained to 6 mo corrected age for a historical cohort of very-low-birth-weight neonates (<1250 g) who were admitted to intensive care over a 7-y period. Neonates with one or more plasma measurements of retinol concentrations < 0.35 micromol/L (<100 microg/L) on days 1-28 were classified as having low vitamin A. BPD was defined at day 28 by clinical and radiologic criteria and by use of supplemental oxygen at 36 wk postmenstrual age (PMA). Dependence on supplemental oxygen was used to identify long-term respiratory disability at 6 mo corrected age. Multivariate logistic regression analyses were conducted. RESULTS: Of the 350 study infants, 192 (55%) had low vitamin A status. BPD occurred in 52% of survivors at day 28 (173/331) and at 36 wk PMA (147/285). Fourteen percent (33/244) required oxygen support at 6 mo corrected age. Adjusted odds ratios of BPD with low vitamin A were 3.5 (95% CI: 1.7, 7.2) at day 28 and 1.7 (1.0, 2.7) at 36 wk PMA. At 6 mo corrected age, the adjusted odds ratio was 2.6 (1.1, 6.4) for respiratory disability with low vitamin A. CONCLUSION: Poor vitamin A status during the first month of life significantly increased the risk of developing BPD and long-term respiratory disability.

Vitamin A status after prophylactic intramuscular vitamin A supplementation in extremely low birth weight infants.

BACKGROUND: Vitamin A supplementation (VAS) is recommended to prevent bronchopulmonary dysplasia (BPD). Our objective was to evaluate the effect of VAS on vitamin A (VA) status. We hypothesized that VAS would improve VA status in extremely low birth weight (ELBW) infants. MATERIALS AND METHODS: Retrospective chart review of infants 1 year before and after initiation of VAS (5000 IU 3 times a week intramuscularly [IM]; total 12 doses). Linear regression was used to model impact of VAS on VA status (retinol level and retinol/retinol binding protein [RBP] ratio). Models were adjusted for time and generalized estimating equations were used to account for intraindividual correlation. RESULTS: Sixty-seven infants (mean gestational age 26 ± 2 weeks; mean body weight 803 ± 142 g) were included; 35 received VAS and 32 did not (no-VAS). Both groups had similar baseline characteristics. Infants who received VAS had mean retinol levels that were 9.0 mcg/dL (95% confidence interval [CI], 4.9-13.2; P < .001) higher and mean retinol/RBP ratios that were 0.21 (95% CI, 0.07-0.36; P = .005) higher than the no-VAS group. Retinol and retinol/RBP ratio increased with time (P < .001). Fewer infants in the VAS group had VA deficiency (retinol/RBP ratios <0.7) compared with the no-VAS group. Culture-positive sepsis was more common in the VAS group (48% vs 12%; P = .002). CONCLUSIONS: VA status in ELBW infants was improved and maintained over the first month of life with IM VAS. Because of concerns for potential risks of repeated injections, further studies are indicated to evaluate the optimal mode of VA delivery in preterm infants.

Zinc protoporphyrin/heme as an indicator of iron status in NICU patients.

OBJECTIVE: Zinc protoporphyrin/heme ratio (ZnPP/H) has been well established as an indicator of functional iron deficiency in subjects 6 months of age to adult. The primary objective of this study was to establish normative values for ZnPP/H in NICU patients and secondarily to explore the utility of this test as an indicator of iron deficiency in neonates. Study design ZnPP/H and complete blood counts were obtained weekly on consecutive NICU patients. Gestational age, growth variables, iron supplementation, erythropoietin treatment, and blood transfusions were documented. Results are reported as mean +/- SD. A value of P <.05 was considered significant. RESULTS: ZnPP/H ratios (n = 639) were evaluated from 143 infants. During the first week of life, ZnPP/H was inversely correlated with gestational age (n = 78, P <.001, r = -0.72). Maternal diabetes, growth retardation, and exposure to chorioamnionitis were independent risk factors for high ZnPP/H. Both iron supplementation and blood transfusion decreased ZnPP/H (P <.001). Erythropoietin treatment was associated with an increase in reticulocyte count and ZnPP/H (P <.001). CONCLUSIONS: ZnPP/H is inversely correlated with gestational age, and the range in all newborn infants is higher than in adults. ZnPP/H is elevated in certain infant subpopulations, which suggests that they may require additional iron supplementation.