Brain damage from hyponatraemia (low blood sodium)

During pregnancy and childbirth women are at increased risk of hyponatraemia (low sodium in the blood). Severe maternal hyponatraemia can cause serious brain injury to the unborn baby. In hospital, hyponatraemia should be prevented by measuring and managing the woman’s fluid intake and output. Fluid management is a basic element of correct nursing and midwifery care. Where a baby suffers brain damage from hyponatraemia as a result of negligent maternity or neonatal care, they may be entitled to claim substantial compensation.

What is hyponatraemia? 

Hyponatraemia is the medical term for too little sodium (salt) in the blood. Our bodies need a correct balance between water and electrolytes (sodium and potassium). Hyponatraemia means that the fluid in the body has become too diluted. 

Is hyponatraemia dangerous?

Mild hyponatraemia can usually be treated without leaving permanent injury. Severe or acute hyponatraemia is dangerous because it can lead to brain swelling (cerebral oedema). This happens because low blood sodium levels allow water to move from the bloodstream into the brain cells, causing them to swell. Cerebral oedema can cause damage to the brain and permanent neurological disability. 

Why are pregnant women and their babies at increased risk of hyponatraemia?

Any condition which disrupts the fluid balance in the body can lead to hyponatraemia. In pregnancy and childbirth, women are more vulnerable to hyponatraemia from fluid imbalance (or water intoxication) owing to a combination of factors which affect their body fluids at this time:

  • In pregnancy a woman’s blood circulation naturally increases in volume to provide blood, nutrients and oxygen through the placenta to the unborn baby. This reduces the balance between fluid and sodium in her blood. This naturally increases her risk.
  • In the third trimester (final three months) of pregnancy, many women experience urine retention which means that less water is passed out of the body. 
  • In labour, the body naturally produces a hormone called oxytocin. This hormone stimulates contractions in the uterus that are necessary for the woman to give birth. Oxytocin is a natural anti-diuretic which further reduces the woman’s ability to urinate and pass water. 
  • If contractions in labour are too weak or slow for labour to be effective, the woman may be given a drug which is very similar to the body’s natural oxytocin. This drug is often known by its trade name, Syntocinon. When a woman is given Syntocinon in labour, this has the same anti-diuretic (water-retaining) effect as oxytocin. Syntocinon is given by a drip with additional intravenous (IV) fluids. This increases the woman’s fluid levels even further. 
  • During the hard work of labour, the woman may be encouraged to drink plenty of water to avoid dehydration. Even where the midwife is noting the woman’s fluid input and output, this additional low-salt fluid intake from drinking water can be missed. A research study into hyponatraemia in labour found that, even amongst low-risk women who hadn’t been given Syntocinon or IV fluid, more than a quarter of women who drank more than 2.5 litres of fluid in labour were hyponatraemic. 

Hyponatraemia in pregnancy and childbirth is also dangerous for the baby. The child is at additional risk of severe brain injury if the mother has no symptoms, or her early symptoms are mistaken for other pregnancy-related conditions, leaving her hyponatraemia undiagnosed. Throughout pregnancy the fetus (unborn baby) shares the mother’s blood circulation and may suffer injury as a result of the mother’s hyponatraemia before the mother shows any symptoms and the condition is diagnosed. 

Can negligent maternity and neonatal care cause brain injury from hyponatraemia?  

When a mother or baby suffers severe injury from hyponatraemia in a hospital setting, it is often the result of errors in fluid management and other mistakes in negligent maternity, nursing or neonatal care. 

Newborn babies with neonatal hyponatraemia may suffer additional harm from delays in treatment of their condition, when their seizures are misinterpreted as signs of hypoxic ischaemic encephalopathy (HIE) and they are incorrectly sent for cooling

Severe, permanent brain damage can also be caused by incorrect treatment of hyponatraemia if the blood sodium concentration is increased too quickly. 

Can I claim compensation for my child’s brain injury from hyponatraemia? 

If your child has suffered cerebral oedema or a brain injury from hyponatraemia caused by mistakes in maternity or neonatal care, they may be entitled to substantial compensation. 

In a recent report, NHS Resolution, the NHS defence organisation, recently warned NHS Trusts that lack of awareness and prevention of hyponatraemia in maternity care is leaving mothers and babies at risk of serious neurological injury.


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