Some babies with hypoxic-ischemic encephalopathy (HIE) may have other health issues relating to the failure or dysfunction of other organs, such as the kidneys, liver or intestines. Why is this?
Babies who have been impacted by birth asphyxia sometimes demonstrate a reflex called the “mammalian diving reflex.” When oxygen supply is limited around the time of birth, blood flow is reflexively shunted away from other organs towards the brain. The body’s natural response is to protect the brain before other bodily organs. Ultimately, this oxygen deprivation can compromise the function of those other organs.
The reflex involves several parts, but at its most basic, it involves a few key elements:
- Bradycardia (a slowed heart rate)
- Peripheral vasoconstriction (the constriction of blood vessels in the limbs and skin)
- The diversion of blood to the brain, adrenal glands, and heart.
This occurs in an attempt to maintain perfusion and oxygen flow to vital organs. However, the reflex can and sometimes does reach its limit, at which point it fails entirely. At the beginning of asphyxia, blood pressure increases, but as the oxygen-depriving event continues and fetal oxygen reserves are depleted, this mechanism begins to fail, dropping blood pressure significantly. As blood pressure drops, blood flow to key tissues decreases, leading to a compromise in both blood and oxygen flow, which can lead to multi-organ failure.
Infants who have been deprived of oxygen also have an altered breathing pattern. At first, they may have a fast rate of respiration to compensate, but if the oxygen deprivation persists, these respirations slow and eventually stop. Some babies can resume breathing with stimulation, while others cannot, requiring positive pressure ventilation to get their breathing going again.
Multi-organ failure is fairly common in severe hypoxic-ischemic encephalopathy, since it means that blood flow was shunted away from other organs to a very significant degree. Knowing the degree of potential damage helps medical practitioners help families understand and plan for the comprehensive care of their child.
- Mammalian Dive Reflex: Examples
- [Research] Multiorgan dysfunction in infants with post-asphyxial hypoxic-ischaemic encephalopathy
- Neurology of the Newborn (Joseph Volpe)