Hyponatraemia - brain injury from low blood sodium caused by fluid monitoring errors in childbirth

We hear a lot about the importance of good hydration. People who are interested in health or fitness make sure that they are drinking plenty of water.

In childbirth, excess water consumption can leave the bloodstream dangerously short of sodium (salt). This leaves the mother and baby at risk of serious neurological injury. The medical term for low blood sodium is hyponatraemia. With correct fluid management, a basic element of nursing care, hyponatraemia should be prevented but cases of baby brain injury from maternal hyponatraemia are on the rise.

NHS defence organisation, NHS Resolution, has recognised hyponatraemia as an emerging theme in maternity and neonatal safety. They have warned that lack of awareness and prevention of this dangerous condition in maternity care is leaving increasing numbers of mothers and babies at risk of serious neurological injury. 

What is hyponatraemia? 

Hyponatraemia means too little sodium (salt) in the blood. It arises from an incorrect balance between the water in the body and the electrolytes (sodium and potassium). In hyponatraemia the fluid has become too diluted. 

Mild hyponatraemia may be symptomless and is easily treatable. Severe or acute hyponatraemia is dangerous because when the blood sodium is too low, water is able to leave the bloodstream and enter the brain cells, causing them to swell. Brain swelling (cerebral oedema) can cause permanent damage to the brain and neurological disability. 

Causes of hyponatraemia include conditions which disrupt the fluid balance in the body, such as:

• medications, such as diuretics (drugs/substances which increase urination, removing salt and fluid from the body);
• severe diarrhoea;
• severe vomiting;
• intestinal obstruction or fistula;
• heart disease or stroke;
• kidney disease;
• liver disease;
• SIADH (a condition in which the body produces excess antidiuretic hormone, causing water retention and low sodium levels);
• surgery or trauma;
• drinking too much of water (dilutional).

Where a patient suffers brain injury from hyponatraemia in hospital, it is usually the result of incorrect fluid management and other mistakes the patient’s care. 

Who is at risk of hyponatraemia? 

Anyone can suffer from hyponatraemia but women are at increased risk during pregnancy, labour and after giving birth. Hyponatraemia isn’t caused by pregnancy but a combination of factors in pregnancy and childbirth make women more vulnerable to hyponatraemia at this time. 

During normal pregnancy a woman’s circulation naturally increases. This reduces her sodium to fluid balance, so from early in the pregnancy she is already at increased risk. Then in the last three months (third trimester) of pregnancy, many women suffer from urine retention, leaving them less able to excrete water. 

During labour, the woman’s body naturally has increased levels of oxytocin, the hormone which stimulates the uterus to contract. Oxytocin is naturally anti-diuretic and causes the labouring woman to retain water. If labour is slow or contractions are weak, women are often given Syntocinon, a synthetic oxytocin drug. This has the same anti-diuretic effect as natural oxytocin. Syntocinon is administered in drip form with IV (intravenous) fluids, further increasing the woman’s fluid intake.

Labour is hard work and the woman may be encouraged to drink water to prevent dehydration. A research study recently found that 26% of low risk mothers who received or drank more than 2.5 litres of fluid in labour were hyponatraemic, compared with only 1% of those who took on less than 1 litre. This was true even where the woman had not received Syntocinon or intravenous fluid. 

This type of birth-related hyponatraemia, caused by a woman taking on more low-sodium fluid than she can excrete, is also known as water intoxication.

What happens when someone is hyponatraemic?

Hyponatraemia is dangerous for both mother and baby. Maternal symptoms of hyponatraemia depend on the severity and speed of the drop in sodium levels. Mild hyponatraemia may be symptomless, and early signs may be mistaken for other conditions, such as pre-eclampsia. A sharp drop in blood sodium can cause cerebral oedema, leading to permanent disability and death. 

Symptoms include:

• nausea;
• lethargy;
• headache;
• agitation;
• confusion or disorientation;
• decreased level of consciousness;
• depressed reflexes;
• abnormal breathing pattern;
• seizures;
• coma;
• death.

As the mother and fetus share the mother’s blood circulation, the unborn baby can be affected by the mother’s hyponatraemia even before the mother shows symptoms. Babies born to mothers with hyponatraemia will also suffer the effects of this life-threatening condition. Babies with brain injury from neonatal hyponatraemia may suffer seizures which can be misinterpreted as signs of HIE (caused by lack of oxygen) and mistakenly sent for cooling.

Hyponatraemia requires very careful management under senior obstetric and anaesthetic supervision to raise the patient’s blood sodium levels to safe levels. If the blood sodium concentration is increased too quickly it can cause irreversible, severe brain damage.

Can negligent maternity care cause brain injury from hyponatraemia?

Hyponatraemia from ‘water intoxication’ in childbirth most commonly arises from incorrect fluid management in hospital. Labouring women’s fluid input and output should be monitored and recorded in their records. Imbalances should be recognised and treated. In a hospital setting, correct fluid management is basic nursing and midwifery care.  

NHS Resolution have identified the risk of severe brain injury to babies from hyponatraemia in childbirth as an emerging theme from its Early Notification Scheme. Worryingly, they refer to several babies who may have suffered serious brain injury from hyponatraemia at birth but say that they are unclear whether these risks/injuries and their cause have been communicated to the affected children’s parents. These parents are entitled to know that if their child has suffered or risks severe, permanent injury from negligent care they should seek independent specialist legal advice as their child may be entitled to substantial compensation.

If you are caring for a child or young adult with cerebral palsy or other neurological disability and would like to find out more about making a claim, contact us by email on cerebralpalsy@boyesturner.com.