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Understanding hypoxic-ischemic encephalopathy (HIE)

Posted: 17/11/2022


What is HIE?

HIE occurs when there is a lack of oxygen or blood flow reaching a baby through the placenta. Broken down, hypoxia means deprivation of oxygen, ischaemia refers to a lack of blood supply, and encephalopathy refers to disease or damage to the brain. HIE often occurs before or during birth, but it can also occur shortly after birth.

The team providing care to the mother during delivery should monitor for warning signs that a lack of oxygen is occurring, such as an abnormal heart rate in the baby, and act appropriately.

However, for a variety of reasons, HIE is not always prevented or treated, and this can affect the baby’s brain, as well as other organs. HIE can lead to a brain injury and, in severe cases, death. Babies who survive may grow up to have disabilities.

What are the symptoms?

A baby suffering a loss of oxygen or blood flow may display:

  • hyper-alertness;
  • irritability;
  • sleepiness;
  • floppiness or stiffness;
  • unusual movements or seizures;
  • pauses in breathing;
  • reduced awareness or responsiveness.

What causes HIE?

Although it is not always possible to determine the reason, common causes of HIE include:

  • prolonged labour – where there has been an unusually long labour;
  • uterine rupture – where the uterus tears;
  • placental abruption – this is when the placenta comes away from the uterus too soon;
  • shoulder dystocia – when the baby’s shoulders get stuck behind the mother’s pubic bone during the birth.

Tests that may be conducted

HIE can be diagnosed via the umbilical cord blood test that is carried out immediately after birth. The team may also use a baby’s APGAR score to help diagnose HIE. The APGAR score is a figure given based on the baby’s appearance, pulse, grimace, activity and respiration at various intervals following birth.

The hospital may conduct cerebral function monitoring (CFM), where sensors are used to monitor brain activity, in order to see the effects of the HIE on the baby’s brain. An ultrasound of the head may also be done, which can show swelling or bleeding on the brain, or an MRI scan which produces detailed pictures of the brain and any damage. An MRI scan is usually conducted after any cooling therapy has been completed.

Treatment of HIE

The medical team will monitor the baby suffering from HIE closely, and may decide to start therapeutic cooling. This involves the use of a special cooling mattress to lower the baby’s temperature between 33-34 degrees for 72 hours, following which the baby is then rewarmed over a period of 12 hours. The cooling must be started within the first six hours after delivery.

Babies may also need ventilation to help them with their breathing, treatment to help increase blood pressure, and close monitoring to check for any seizures that may occur.

Long-term consequences of HIE

HIE can cause difficulties with breathing and feeding, as well as low muscle tone in babies.

Some babies recover fully following HIE, whereas others will develop long-term disabilities. The extent of their difficulties will vary, and some go on to need ongoing support from healthcare professionals. All babies affected by HIE will need to be closely monitored and reviewed regarding their development. They may have issues with language development, their motor skills (moving about), their thinking and cognition, or their sensory abilities - sight, touch, smell, hearing and taste.

A common disability that occurs as a result of severe cases of HIE is cerebral palsy, a group of conditions which can include developmental delay and long-term difficulties with movement, and sometimes with learning. HIE can also lead to epilepsy, a condition that causes recurrent seizures.

If you have any concerns about the management of your pregnancy or labour and your baby suffered from HIE, our team is available to discuss whether there may have been errors in your care, and if HIE could have been avoided had appropriate treatment been provided.

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