11 Aug Long Term Hypoxic Events Linked To Adverse Outcomes In Very Preterm Infants
Medical Research: What is the background for this study?
Prof. Poets: Episodes of intermittent hypoxemia (lack of oxygen) and bradycardia (slow heart rate) are common in very preterm infants and often a subject of considerable concern. However, up to now there has been a lack of knowledge as to how often or how long such episodes may occur without increasing an infant’s risk for impaired development or even death.
In this study, we utilized long-term recordings (lasting 8-12 weeks) of oxygen saturation and heart rate obtained as part of the Canadian Oxygen Trial (COT), a large study performed in extremely immature infants and comparing a higher with a lower oxygen saturation target range (85-89 vs. 91-95% oxygen saturation measured by pulse oximetry). For this secondary analysis, we wanted to test the hypotheses that spending a high proportion of time at an oxygen saturation below 80% or a pulse rate <80 beats per minute increases the risk of the following adverse outcomes:
- Death after reaching a post-menstrual age of 36 weeks (i.e. 4 weeks before their due date) or disability, determined at 18-22 months corrected age and defined as motor impairment, cognitive or language delay, severe hearing loss, or bilateral blindness;
- Motor impairment (determined at 18-22 months corrected age);
- Cognitive or language delay (determined at 18-22 months corrected age);
- Severe retinopathy of prematurity.
Medical Research: What are the main findings?
Prof. Poets: Analyzable recordings and outcome data were available for 1019 infants, of which the least affected 10% spent 0.4%, and the most affected infants 13.5% of the time at an oxygen saturation <80%. We found that the risk to develop all of the adverse outcomes mentioned above increased with the percentage of time spent at an oxygen saturation below 80%, but this was true only for hypoxemic events lasting for at least 1 minute. Episodes with a low heart rate (in the absence of concomitant hypoxemia) were not associated with an increased risk of an adverse outcome. Interestingly, hypoxemic events occurring in infants originally randomized to the higher oxygen group in the original COT study were associated with a stronger increase in the risk of death or disability than such episodes occurring infants randomized to the lower oxygen saturation target range.
Medical Research: What should clinicians and patients take away from your report?
Prof. Poets: There is good news and bad news in these data:
The good news is that it is reassuring that only the (comparatively rare) events lasting for 1 minute or more were associated with an adverse outcome, and that episodes with a slow heart rate added very little to this risk.
The bad news is that prolonged episodes with a low oxygen saturation (<80%) are clearly of concern, as they may affect long-term development, at least if our findings are confirmed in future studies.
Medical Research: What recommendations do you have for future research as a result of this study?
Prof. Poets: If our findings are confirmed in future studies, increased efforts to prevent or treat (shorten) such episodes are needed. This may involve a closer look at interventions that are yet only insufficiently tested, such as higher caffeine doses, doxapram administration, or specific ventilator strategies.
Christian F. Poets MD, Robin S. Roberts MSc, Barbara Schmidt MD, MSc, Robin K. Whyte MB, Elizabeth V. Asztalos MD, MSc, David Bader MD, Aida Bairam MD, PhD, Diane Moddemann MD, Abraham Peliowski MD, Yacov Rabi MD, Alfonso Solimano MD, Harvey Nelson MSc
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Prof. Dr. med. Christian F. Poets (2015). Long Term Hypoxic Events Linked To Adverse Outcomes In Very Preterm Infants MedicalResearch.com