Genetic variation in CYB5R3 is associated with methemoglobin levels in preterm infants receiving nitric oxide therapy

The Controversy Persists: Is There a Qualification Criterion to Utilize Inhaled Nitric Oxide in Pre-term Newborns?

Inhaled nitric oxide (iNO) use in premature newborns remains controversial among clinicians. In 2014, the American Academy of Pediatrics, Committee on Fetus and Newborn released a statement that the available data do not support routine iNO use in pre-term newborns. Despite the absence of significant benefits, 2016 California data showed that clinicians continue to utilize iNO in pre-term infants. With studies as recent as January 2017, the Cochrane review confirmed no major advantages of iNO in pre-term newborns. Still, it recognized that a subset of pre-term infants with pulmonary hypertension (PHTN) had not been separately investigated. Furthermore, recent non-randomized controlled trials have suggested that iNO may benefit specific subgroups of pre-term newborns, especially those with PHTN, prolonged rupture of membranes, and antenatal steroid exposure. Those pre-term infants who showed a clinical response to iNO had increased survival without disability. These findings underscore the need for future studies in pre-term newborns with hypoxemic respiratory failure and PHTN. This review will discuss the rationale for using iNO, controversies regarding the diagnosis of PHTN, and additional novel approaches of iNO treatment in perinatal asphyxia and neonatal resuscitation in the pre-term population < 34 weeks gestation.

Life-Threatening Extreme Methemoglobinemia during Standard Dose Nitric Oxide Therapy

We report the first case of life-threatening extreme neonatal-acquired methemoglobinemia that occurred during inhaled nitric oxide (iNO) at the standard 20 ppm dose in a neonate with early onset sepsis and suprasystemic pulmonary hypertension. Life-threatening methemoglobinemia has been efficaciously treated with methylene blue and ascorbic acid, while stopping iNO and starting iloprost and sildenafil. The patient was subjected to various tests (including gene sequencing and hemoglobin electrophoresis) and did not have any known genetic cause or predisposition for methemoglobinemia. Neuroimaging and the 2-year clinical follow-up were completely normal.

Utility of routine methemoglobin laboratory assays in critically ill pediatric subjects receiving inhaled nitric oxide

PURPOSE

Inhaled nitric oxide (iNO) has been associated with safety risks including reports of methemoglobinemia. While standard of care recommends routine monitoring of methemoglobin in subjects on iNO therapy, the utility of this practice remains unknown.

MATERIALS AND METHODS

This retrospective chart review aimed to determine the frequency of methemoglobinemia in pediatric patients receiving iNO. Included subjects were under 18 years of age receiving iNO therapy with at least one methemoglobin concentration measured from 10/18/2014 to 11/18/2016.

RESULTS

In total, 1809 methemoglobin concentrations were collected in 247 subjects during the study period. Median age was 0.33 (0.04-0.83) years. The mean methemoglobin concentration was 1.33% (±0.42) while receiving a mean iNO dose of 11.71 ppm (±7.97). Twenty-nine subjects had a total of 131 methemoglobin concentrations analyzed while receiving iNO doses above 20 ppm which were similar to the entire cohort at 1.33% (±0.42); (p = .95).

CONCLUSIONS

Pediatric patients receiving iNO at doses below 40 ppm have minimal risk of developing clinically significant methemoglobinemia. Routine, ongoing monitoring of metHb levels in all pediatric subjects receiving iNO therapy at doses <40 ppm without the presence of risk factors predisposing the subject to increased risk of methemoglobinemia is unnecessary and should be avoided.

Genome-Wide Estimates of Heritability for Social Demographic Outcomes

An increasing number of studies that are widely used in the demographic research community have collected genome-wide data from their respondents. It is therefore important that demographers have a proper understanding of some of the methodological tools needed to analyze such data. This article details the underlying methodology behind one of the most common techniques for analyzing genome-wide data, genome-wide complex trait analysis (GCTA). GCTA models provide heritability estimates for health, health behaviors, or indicators of attainment using data from unrelated persons. Our goal was to describe this model, highlight the utility of the model for biodemographic research, and demonstrate the performance of this approach under modifications to the underlying assumptions. The first set of modifications involved changing the nature of the genetic data used to compute genetic similarities between individuals (the genetic relationship matrix). We then explored the sensitivity of the model to heteroscedastic errors. In general, GCTA estimates are found to be robust to the modifications proposed here, but we also highlight potential limitations of GCTA estimates.