Oxygen deprivation at birth: protecting vulnerable newborns from brain damage

Published on 22 November 2011

Worldwide, nearly one quarter of babies who die within a month of birth lose their lives to a problem called birth asphyxia or perinatal asphyxia – oxygen deprivation and a reduced blood supply to the brain around the time of birth that lasts long enough to be harmful.¹ Professor Marianne Thoresen at the University of Bristol is hoping to boost these babies’ chances, by investigating how two different interventions – cooling therapy and ventilation with different oxygen concentrations – work best together.

What is the problem and who does it affect?

In the UK, around one in 500 babies born at full term – 1,400 babies every year – suffers a shortage of oxygen and reduced blood supply to the brain around the time of birth that is severe enough to threaten their health.² This problem, often known as perinatal asphyxia, is a major cause of death and disability in babies worldwide.³ Causes include problems with the umbilical cord or placenta.

“Perinatal asphyxia can be devastating, putting babies’ lives in immediate danger,” explains Professor Marianne Thoresen. “Babies who survive are at serious risk of developing life-long problems, such as cerebral palsy and learning disabilities. Some are so badly affected they cannot move, speak or care for themselves.”

Babies who have suffered perinatal asphyxia often need prolonged help with breathing – using assisted ventilation – after birth. The same babies often also stand to benefit from cooling therapy, which involves reducing their body temperature from 37 to 33.5°C for three days. ‘We think that giving babies assisted ventilation, using air, while also cooling them for three days after birth could improve their chances by protecting the brain, but we lack evidence on the best way to combine these two interventions’, explains Professor Thoresen.

What is the project trying to achieve?

“We are gathering laboratory evidence on how to combine cooling therapy with assisted ventilation, using different oxygen concentrations in the breathing circuit,” explains Professor Thoresen. “We hope to help boost the chances of babies who need both treatments, such as babies with severe perinatal asphyxia.”

Recently, studies revealed that using 100% oxygen during assisted ventilation after birth can actually damage the brain, so the international guidelines were changed, to recommend using normal air. However, it is still unclear exactly what level of oxygen is best and for how long after birth breathing high levels of oxygen might be damaging.

“We are looking for answers to two important questions,” explains Professor Thoresen: “Firstly, ‘How might different oxygen concentrations affect babies’ chances of surviving, and escaping brain damage, if they do, or do not, receive cooling therapy?’ And secondly, ‘Could there be any differences between what works best for babies who are born at full term and babies who are born prematurely?’”

The team’s work, which uses a laboratory model, will help pave the way to clinical trials in babies.

What are the researchers’ credentials?

The track record of the project leader, Professor Marianne Thoresen, and her department is outstanding. Professor Thoresen was a key contributor to the development of cooling therapy, which has become standard treatment for many babies with severe birth asphyxia in developed countries, being recommended by both the National Institute for Health and Clinical Excellence (NICE) in the UK and international guidelines⁴.

References

1. Bryce J, et al. WHO estimates of the causes of death in children. Lancet 2005; 365:1147-52.
2. Kurinczuk J et al. Epidemiology of neonatal encephalopathy and hypoxic-ischaemic encephalopathy. Early Human Development 2010; 86:329-38.
3. McGuire W. Perinatal asphyxia. ClinicalEvidence 2007; 7 Nov. http://clinicalevidence.bmj.com/ceweb/conditions/chd/0320/0320_backgroun... (website accessed 28 September 2011).
4. National Institute for Health and Clinical Excellence. Therapeutic hypothermia with intracorporeal temperature monitoring for hypoxic perinatal brain injury (Interventional procedure guidance 347). May 2010 (http://www.nice.org.uk/nicemedia/live/11315/48809/48809.pdf