Neonatal Updates

There’s been a lot of good stuff published recently, so time for a couple of Neonatal Updates. First the most recent (May) issue of the Archives Fetal and Neonatal edition was packed with interesting publications.(including 2 I have already blogged about).

Salas AA, et al. A randomised trial of re-feeding gastric residuals in preterm infants. Archives of Disease in Childhood – Fetal and Neonatal Edition. 2015;100(3):F224-F8. In this study 72 infants, between 23 and 29 weeks gestation, who were getting minimal enteral nutrition/trophic feeds during the first week of life were randomized to either have their residuals re-fed, or thrown away, whenever the residual was over 1/3 of the feed volume or over 2 mL. There were no substantial differences in outcomes between the groups, but a lot of babes in each group (around 40%) had an episode of interruption of their feeds for at least 12 hours.

Big question.. why evaluate gastric residuals at all? We stopped routinely aspirating prior to feeds a few years ago, and the only apparent effect has been a reduction in the number of babies who have an episode of feeding interruption. This study shows that if you do still measure them, at least you can give them back.

Coste F, et al. Ventilatory control and supplemental oxygen in premature infants with apparent chronic lung disease. Archives of Disease in Childhood – Fetal and Neonatal Edition. 2015;100(3):F233-F7. This takes me back… when I was a fellow I started a study looking at the respiratory control effects of hypoxic, hyperoxic, and 2% CO2 challenges on infants with BPD. Enrollment was very slow and I finished fellowship with only 3 or 4 patients, leading to some data in a drawer, but no publication. One of the reasons for doing it was that some people had suggested that babies with BPD were like adults with COPD, reliant on hypoxic drive, and liable to become hypercarbic if you gave them too much oxygen. In fact, it was clear from reading the literature that that was not true for adults with COPD at all (even though it was still being taught to medical students, maybe it still is), in fact hypoxic drive is suppressed in adults with chronic hypoxia, and the minor increase in CO2 that occurs when you increase, or start, supplemental oxygen is due to effects on VQ matching (I think it was Michel Aubier who proved that). So I thought it was likely that hypoxic drive was impaired in babies with BPD, and that it was important to give them enough oxygen to maintain a good PO2 (this was started in the days before pulse oximeters). The little data I had, showed no increase in transcutaneous CO2 when I increased the oxygen administered, and an intact CO2 response.

This new paper enrolled babies undergoing the physiologic challenge at 36 weeks to see if they satisfied Michele Walsh’s physiologic definition of BPD. About 1/4 of the babies who were able to get down to 21% passed the test, the other 3/4 becoming too hypoxic to stay off oxygen. Infants developed unstable breathing when the oxygen was stopped with frequent appearance of periodic breathing. Interestingly this happened to the babies who passed the test, as well as to those who failed. So even if you pass the O2 discontinuation test, the fact that you were still receiving oxygen or resp support at 36 weeks was a sign that your respiratory control was still not optimal.

Kaandorp JJ, et al. Maternal allopurinol administration during suspected fetal hypoxia: a novel neuroprotective intervention? A multicentre randomised placebo controlled trial. Archives of Disease in Childhood – Fetal and Neonatal Edition. 2015;100(3):F216-F23. Over 200 women with signs of fetal hypoxia during labour were randomized to allopurinol or placebo prior to delivery. Despite all the prior evidence that inhibiting xanthine oxidase, thus reducing free radical production, is protective in animal studies. This multicenter RCT was not able to show benefit, either on the primary outcome, which was on a biomarker of brain injury, S100ß, or on any clinical outcomes. Of course, as we are so poor in predicting significant perinatal depression/encephalopathy from clinical indicators prior to birth, most of the babies were fine, with only a mild reduction in mean cord pH compared to the population (7.19). On posthoc analysis girls did have some reduction in the S100ß, but I can’t see if the interaction term was significant, so that tends to look at bit unreliable.

I don’t think this spells the end of allopurinol, the animal data, and the safety demonstrated by this trial suggests that it is worth pursuing. We just need ways to predict more accurately which babies might benefit.

About Keith Barrington

I am a neonatologist and clinical researcher at Sainte Justine University Health Center in Montréal
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