ACTA Project Grant
Pilot study of near-infrared reflectance spectroscopy in children's heart surgery
Dr Jayant Pratap
Background:
Almost 5000 children undergo heart surgery each year in the UK. Many suffer complications when surgeons stop the heart to operate on it, resulting in inadequate blood supply to vital organs despite using an artificial pump instead. Even when restarted the heart is weakened. Intensive care medicine is now so effective that death is fortunately now uncommon, but long-lasting disability remains frequent. Brain damage is especially feared and affects up to 60% undergoing surgery in the newborn period. We suspect such problems occur because current monitoring technologies do not indicate poor vital-organ blood supply until too late.
Aims:
We would like to find out if Near-Infrared Reflectance Spectroscopy (NIRS) is a better
monitoring technology. NIRS requires simply a low-power source and detector placed on the skin. Evidence already exists that NIRS may alert the surgical team to organ compromise even when other monitoring does not, allowing them to act sooner. There is also some data to indicate how low the NIRS value can be - and for how long - before brain function is affected (albeit temporarily). A link has even been shown between prolonged episodes of low NIRS readings and new abnormalities on a subsequent sensitive brain-imaging scan. However the long-term significance remains undetermined, particularly as we do know that brains of very young children sometimes overcome damage which adults cannot. NIRS technology is very expensive, and we do not know if reacting to displayed values improves the outcome for children. There is no agreed way to interpret or respond to NIRS in children. As assessing for brain damage is very difficult in small children, we propose a small 'pilot' study to test an algorithm for reversing low NIRS readings. We will also study more practical ways to measure any benefits of NIRS in future research.
Methodology:
We will study 30 children under 1 month old, undergoing heart surgery at Great Ormond
Street Hospital, with their parents' permission. All will be monitored during surgery using an approved commercial NIRS monitor. For half the display will be electronically switched off, such that knowledge of the NIRS readings does not affect the surgery, though recording continues to allow later analysis. For the remainder NIRS monitoring will be displayed throughout surgery, along with evidence-based guidance as to how the surgical team should respond. As only a proportion of well-regarded children's heart surgery units currently use NIRS routinely, we believe this is ethical and fair to trial participants.
Expected outcomes:
NIRS traces will be compared to confirm if our algorithm is effective. We will later look at
the intensive care charts and notes, and results of routine tests, to see if any measures
suggest that NIRS made a difference in outcome.
Implications:
If our algorithm for managing low NIRS values is effective, and our trial methods work well, we will establish a larger trial to test if NIRS really improves the outcome of children undergoing heart surgery. Should NIRS monitoring prove ineffective, this knowledge will permit NHS funds to be spent more appropriately.
