The impact of intermittent hypoxemia on type 1 retinopathy of prematurity in preterm infants.

BACKGROUND: Intermittent hypoxemia (IH) may influence retinopathy of prematurity (ROP) development in preterm infants, however, previous studies had mixed results. This study tests the hypothesis that increased IH is associated with Type 1 ROP; a stage beyond which treatment is indicated. METHODS: IH was quantified by continuously monitoring oxygen saturation (SpO2) using high-resolution pulse oximeters during the first 10 weeks of life. Statistical analyses assessed the relationship and predictive ability of weekly and cumulative IH for Type 1 ROP development. RESULTS: Most analyses showed no association between IH and Type 1 ROP adjusting for gestational age (GA) and birth weight (BW). However, cumulative IH of longer duration during weeks 5-10, 6-10, and 7-10 were significantly associated with Type 1 ROP adjusting for GA and BW, e.g., the adjusted odds ratio of Type 1 ROP was 2.01 (p = 0.03) for every 3.8 seconds increase in IH duration from week 6-10. IH did not provide statistically significant added predictive ability above GA and BW. CONCLUSIONS: For most analyses there was no significant association between IH and Type 1 ROP adjusting for GA and BW. However, infants with longer IH duration during the second month of life had higher risk for Type 1 ROP. IMPACT: The relationship and predictive ability of intermittent hypoxemia (IH) on retinopathy of prematurity (ROP) is controversial. This study shows no significant association between IH events and Type 1 ROP after adjusting for gestational age (GA) and birth weight (BW), except for cumulative IH of longer duration in the second month of life. In this cohort, IH does not provide a statistically significant improvement in ROP prediction over GA and BW. This study is the first to assess the cumulative impact of IH measures on Type 1 ROP. Interventions for reducing IH duration during critical postnatal periods may improve ROP outcomes.

Case series of therapeutic hypothermia for neonatal hypoxic-ischemic encephalopathy during extracorporeal life support.

Therapeutic hypothermia initiated within 6 hours of birth is currently the standard of care for the management of neonates with hypoxic-ischemic encephalopathy. Neonates undergoing therapeutic hypothermia for hypoxic-ischemic encephalopathy are also at risk for severe respiratory failure and need for extracorporeal life support. The risks and benefits of therapeutic hypothermia for hypoxic-ischemic encephalopathy during extracorporeal life support are still not well defined. We report our experience of a case series of six neonates who underwent therapeutic hypothermia for hypoxic-ischemic encephalopathy during extracorporeal life support. We also report long-term neurodevelopmental follow-up from 6 to 24 months and add to the current body of evidence regarding feasibility, clinical experience, and short-term complications.

Blood transfusions in preterm infants: changes on perfusion index and intermittent hypoxemia.

BACKGROUND: Red blood cell (RBC) transfusion decreases intermittent hypoxemia (IH) events beyond the first week of life. This benefit may be related to improved perfusion to the respiratory control network. Perfusion index (PI) is a perfusion measure provided by the pulse oximeter. We hypothesized that the benefit in IH after RBC transfusion is associated with an increase in PI. In addition, we assessed the value of PI and clinical measures in predicting the effect of RBC transfusion on IH. STUDY DESIGN AND METHODS: We prospectively enrolled infants less than 30 weeks' gestation age. PI and oxygen saturation (SpO2 ) were monitored with high-resolution pulse oximeters 24 hours before and after RBC transfusion. Data were analyzed at three postnatal periods: Epoch 1, first week of life (1 to 7 days of life); Epoch 2, 2 to 4 weeks of life (8 to 28 days of life); and Epoch 3, 4 to 8 weeks of life. RESULTS: A total of 118 transfusions were analyzed. IH measures significantly decreased after transfusion in Epochs 2 and 3. PI significantly increased after transfusion, but it did not correlate with the decrease in IH measures. Mechanical ventilation, fraction of inspired oxygen (FiO2 ), and IH measures influenced the effects on oxygenation. CONCLUSIONS: RBC transfusion improved IH after the first week of life. The benefit in IH did not correlate with PI increase after transfusion. Pretransfusion respiratory support and IH measures predicted the effect of transfusion on oxygenation.

Comparison of multiple red cell volume methods performed concurrently in premature infants following allogeneic transfusion.

BACKGROUND: Study of the pathophysiology and treatment of anemia of prematurity is facilitated by direct measurement of red cell volume (RCV) utilizing microliter quantities of blood samples. Our objective was to compare concurrent measurements of multiple direct RCV methods in infants. METHODS: Eighteen preterm infants receiving clinically indicated transfusions had concurrent flow cytometric determinations of RCV and 24-h red blood cell (RBC) recovery based on donor-recipient differences of biotin-labeled RBCs (BioRBCs), Kidd antigen mismatched RBCs, and fetal hemoglobin-positive (HbF(+)) RBCs. High-performance liquid chromatography (HPLC) was also used for measuring HbF and adult hemoglobin protein concentrations for the determination of RCV. RESULTS: Concurrent RCV measurements using BioRBCs (18 and 54 µg/ml), Kidd antigen, and HbF flow cytometry were not statistically different compared with RCVs measured using the reference BioRBC density (6 µg/ml). By contrast, the HbF-HPLC method overestimated RCV by 45% compared with the reference method. All the methods demonstrated 100% 24-h posttransfusion RBC recovery (PTR24). CONCLUSION: Because BioRBC, Kidd antigen, and fetal hemoglobin (HbF) flow cytometry are safe and accurate methods requiring <10 µl of patient blood for determining RCV and PTR24 in preterm infants, they can be useful in clinical and research studies of anemia and other conditions.

The Impact of Intermittent Hypoxemia on Type 1 Retinopathy of Prematurity in Preterm Infants.

Background: Intermittent hypoxemia (IH) may influence retinopathy of prematurity (ROP) development in preterm infants, however, previous studies had mixed results. This study aims to assess the influence and evaluate the predictive ability of IH measures on Type 1 ROP, a stage beyond which ROP treatment is indicated. Methods: IH was quantified by continuously monitoring oxygen saturation (SpO2) using high-resolution pulse oximeters during the first 10 weeks of life. Statistical analyses assessed the relationship and predictive ability of weekly and cumulative IH variables for Type 1 ROP development. Results: Univariate analyses suggested that IH measures are greater in infants with Type 1 ROP and are predictive of Type 1 ROP development. Multivariable logistic regression analyses revealed that cumulative IH of longer duration during certain postnatal periods are associated with Type 1 ROP development after adjusting for gestational age (GA) or birth weight (BW). Although area under the curve (AUC) analyses revealed added predictivity of cumulative IH variables above GA or BW, these increments in AUC were not statistically significant. Conclusions: The duration of IH events was associated with Type 1 ROP development. Interventions for reducing the duration of IH events may potentially improve ROP outcomes.

Hollow Fiber Oxygenator Composition Has a Significant Impact on Failure Rates in Neonates on Extracorporeal Membrane Oxygenation: A Retrospective Analysis.

In extracorporeal life support (ECLS), there are two main types of oxygenators in clinical use for neonates: polymethylpentene (PMP) hollow fiber and polypropylene (PP) hollow fiber. A retrospective study was performed on neonates ( n = 44) who had undergone ECLS for noncardiac indications from 2009 to 2015. Between the two groups (PMP n = 21, PP n = 23), the PP oxygenators failed 91% of the time, whereas the PMP oxygenators failed 43% of the time ( p < 0.05). Analysis suggests PMP oxygenators are less prone to failure than PP oxygenators, and they require fewer number of oxygenator changes during a neonatal ECLS.

Reduced blood pressure of CFTR-F508del carriers correlates with diminished arterial reactivity rather than circulating blood volume in mice.

The F508del mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) is the most common cause of cystic fibrosis (CF). Both CF patients and F508del carriers have decreased blood pressure. While this has been attributed to salt depletion, recent studies have shown F508del expression interferes with smooth muscle cell calcium mobilization. We tested the hypothesis that carriers of the F508del mutation have lower adult blood pressures and reduced aortic contractility without a reduction in circulating blood volume. By radiotelemetry, F508del heterozygous mice had significantly lower arterial pressures than wild-type C57BL/6 controls, with the greatest effect seen at the time of dark-to-light cycle transition (mean difference of 10 mmHg). To replicate the vascular effects of sympathetic arousal, isoproterenol and epinephrine were co-infused, and F508del mice again had significantly reduced arterial pressures. Aortas isolated from F508del heterozygous mice had significantly decreased constriction to noradrenaline (0.9 ± 0.2 versus 2.9 ± 0.7 mN). Inhibition of wild-type CFTR or the inositol triphosphate receptor replicated the phenotype of F508del aortas. CFTR carrier status did not alter circulating blood volume. We conclude the CFTR-F508del mutation decreases aortic contractility and lowers arterial pressures. As a cAMP-activated chloride channel that facilitates calcium mobilization, we speculate wild-type CFTR co-activation during adrenergic receptor stimulation buffers the vasodilatory response to catecholamines, and loss of this compensatory vasoconstrictor tone may contribute to the lower arterial pressures seen in heterozygote carriers of a CFTR-F508del mutation.