The human body needs glucose to function. Hypoglycaemia occurs when levels of blood glucose are too low.
Under normal conditions, levels of blood glucose are carefully maintained by the body. When blood glucose levels rise, the body releases insulin and glucose is turned into glycogen which can be stored in the body, thereby reducing the amount of glucose in the blood and blood glucose levels are restored. Conversely, when blood glucose levels drop, glycogen is turned back into glucose and once again, blood glucose levels are maintained.
Before a baby is born, they rely on their mother for glucose which is delivered almost continuously via the placenta. When a baby is born it needs to adjust because the supply of glucose changes from being continuous to being intermittent and delivered during times of feeding. During periods between feeds, a baby may use their stores of glycogen but it is possible for these stores to become exhausted and during the first day of life it is common for a babyās blood glucose to fall.
The stages of neonatal hypoglycaemia
Dr Jane Hawdon of Barts Health NHS Trust describes the stages of neonatal hypoglycaemia as follows:
- Low blood glucose levels are found but the baby does not have clinical signs as the baby is still able to draw on alternative fuel stores, for example, glycogen and fat.
- If untreated, the baby exhausts alternative fuel stores and develops subtle clinical signs but hypoglycaemia is not damaging at this stage.
- If untreated, the baby develops obvious and severe clinical signs but may escape damage if treated very promptly.
- If not treated sufficiently soon after onset of clinical signs, hypoglycaemia becomes damaging and in severe cases results in cardiorespiratory arrest.1
What are the symptoms of neonatal hypoglycaemia?
According to a study by Robert and Susan Vannucci, both Professors of Paediatric Neurology2, symptoms of neonatal hypoglycaemia include, most commonly:
- Reduced consciousness; and
- Tremor/jitters;
With more severe hypoglycaemia resulting in:
- A reduced rate of breathing;
- Irritability;
- A high pitched cry;
- Seizures;
- Coma; and
- Cardiac arrest.
What are the risk factors for neonatal hypoglycaemia?
Babies are at a higher risk of neonatal hypoglycaemia if they:
- Have been exposed to growth restriction during the pregnancy: Babies who have been exposed to intrauterine growth restriction have had access to reduced levels of glucose for a while, resulting in energy stores being used up and leaving the newborn baby vulnerable to hypoglycaemia.
- Have a mother with diabetes: Pregnant women with diabetes have elevated glucose in the blood and this causes elevated glucose levels in the baby. This can cause a baby to generate too much insulin. When the baby is born and no longer has access to the elevated levels of glucose from their mother, they still produce too much insulin and the insulin causes the babyās glucose levels to fall, causing hypoglycaemia.
- Have been exposed to a shortage of oxygen: If oxygen levels drop, a babyās metabolism will increase and use up more glucose than usual and this can lead to hypoglycaemia.
How does neonatal hypoglycaemia affect the brain?
Unfortunately, on rare occasions, the signs of hypoglycaemia are not spotted quickly enough. Without enough glucose in the blood, the brain is deprived of energy which can result in brain damage.
The extent of the brain damage will depend on how low the blood sugars dropped and for how long for.
Severe, prolonged neonatal hypoglycaemia has been considered to cause a distinct pattern of brain injury involving the occipital and parietal lobes, positioned towards the sides and back of the brain. However, in a study by Burns et al from the Department of Paediatrics at Imperial College Healthcare NHS Trust3 looking at radiological patterns of brain injury following neonatal hypoglycaemia, it was found that neonatal hypoglycaemia can affect the brain in a much more widespread way than originally thought.
What are the long term consequences of neonatal hypoglycaemic brain injury?
The long-term consequences of neonatal hypoglycaemic brain injury will depend on the area of the brain that is damaged and the extent of that damage.
Damage to the occipital lobe of the brain is often associated with a squint and visual impairment.
Other long-term difficulties after neonatal hyperglycaemic brain injury may include cognitive impairment; developmental delay; epilepsy; and cerebral palsy.4
Is neonatal hypoglycaemia avoidable?
The British Association of Perinatal Medicine has produced a Framework for Practice, providing guidance on the identification and management of neonatal hypoglycaemia.5
The guidance provides that babies who are at risk of neonatal hypoglycaemia should be assessed regularly for feeding and blood glucose monitoring.
Rennie and Robertonās textbook of neonatology6 recommends that at risk babies should be fed within 1 hour of birth and at least every 3 hours thereafter and should have their glucose level checked before their second feed.
On rare occasions, symptoms of neonatal hypoglycaemia may be missed and there may be a delay in treatment that has caused brain injury. If a baby has suffered brain damage as a result of a delay in treating low blood sugar, it may be possible to recover compensation to provide them with the necessary treatment and care for the rest of their life.
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About the author
Experienced in both Medicine and Law, Abigail Ringer is a Senior Associate in the Medical Negligence team at Brain Injury Group member firm RWK Goodman. Abigail manages all new birth injury cases which have resulted in a brain injury to the baby.
Reference
1 Hawdon, 2013. Definition of neonatal hypoglycaemia: time for a rethink? Arch Dis Child Fetal Neonatal Ed September 2013 Vol 98 No 5
2 Vannucci, R.C., et al. (2001). Hypoglycemic brain injury. Semin Neonatol 6(2): 147-55.
3 Burns, C.M., et al. (2008). Patterns of cerebral injury and neurodevelopmental outcomes after symptomatic neonatal hypoglycemia. Pediatrics 122(1): 65-74.
4 Montassir et al (2009). Associated factors in neonatal hypoglycemic brain injury. Brain & Development 31 (2009) 649ā656
5 Identification and Management of Neonatal Hypoglycaemia in the Full Term Infant (2017) | British Association of Perinatal Medicine (bapm.org)
6 Rennie, J.M., Ed. (2005). Roberton’s Textbook of Neonatology. 4th Edition, Elsevier
Churchill Livingstone. Page 856.
