Under Pressure….

Colm O’Donnell once wrote an article with a whole line from a David Bowie song embedded in the article’s title (O’Donnell CPF. Turn and face the strange – ch..ch..ch..changes to neonatal resuscitation guidelines in the past decade. Journal of Paediatrics and Child Health. 2012;48(9):735-9), I think Gene Dempsey is following suit, but using only the title this time, see below! It might have been difficult to include the line “this is our last dance, this is ourselves, under pressure” to treat hypotension.

Faust K, et al. Short-term outcome of very-low-birthweight infants with arterial hypotension in the first 24 h of life. Archives of Disease in Childhood – Fetal and Neonatal Edition. 2015. There have been a number of observational studies of the association between hypotension and clinical outcomes in the very preterm infant. The results have been variable, as the accompanying editorial from Gene Dempsey (Dempsey EM. Under pressure to treat? Archives of Disease in Childhood – Fetal and Neonatal Edition. 2015) points out. One of the reasons for that variability has been the variation in the criteria used for the diagnosis of hypotension. There have been several biases in other published studies, and all observational studies risk biases which are not necessarily obvious.

This particular study was well performed, but of course cannot determine causality, and suffers from not being able to report the duration of the hypotension. What they showed was that there was a statistical association between having a lower blood pressure during the first 24 hours of life, and having more complications (specifically IVH, BPD and death). One of the questions that has been asked about previous data is whether the association might be explained by adverse effects of the interventions that were used for the hypotension. In this data set treatment with pressor agents had a very strong association with IVH and BPD, even after multivariate correction. As Gene points out in his editorial, there were many infants who were hypotensive who were not treated with pressors. Hypotension remains very common, depending on the definition, using the common definition of a mean blood pressure less than the gestational age in weeks, there were about half of the babies who were hypotensive, much as shown in other studies. nevertheless less than 9% of the babies received pressor agents.

So the neonatologists in the network were already selecting who to treat based on some factors other than just the blood pressure. One of the nice things about this study is that they analyze their data among those who did not receive BP support in the first 24 hours, they showed a minor increase in risk of IVH, BPD and death in hypotensive babies who did not receive inotropes, compared to the normotensive. The Odds ratios are between 0.95 and 0.97 and are statistically significant. I think that is the first time this has been shown. Of course it doesn’t mean that the hypotension was causally related to those outcomes, and it certainly doesn’t mean that treatment with inotropes improves the risks. Indeed the Odds ratios for those same complications are much greater for treatment with inotropes, 1.5 to 2.4, which might be because the babies were more unwell, or might be due to the intervention.

This valuable additional data reinforces the need to get prospective trials completed, no matter how difficult they may be.

About keithbarrington

I am a neonatologist and clinical researcher at Sainte Justine University Health Center in Montréal
This entry was posted in Neonatal Research and tagged , , , , . Bookmark the permalink.

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