Heel prick blood tests DO hurt your baby, says study

Babies may find heel prick blood tests far more painful than doctors realise, a study suggests.

Researchers say some procedures often carried out on newborn infants trigger a pain response in the brain – even though the children appear to be unperturbed.

The findings could have implications for the way seriously ill babies are treated in hospital, particularly those given repeated injections or blood tests.

Past studies have shown that babies who do experience a lot of pain in the first few months of life can develop extreme sensitivity to pain as they get older.

Dr Rebeccah Slater, who carried out the study at University College London, said doctors needed better methods for assessing the suffering of babies.

Conventional measures of infant pain, which look for changing heart rates and grimaces, may underestimate what they are feeling.

'Some babies go through many painful procedures each day,' she said. 'There is a risk it can change the way that they respond to pain in the future.'

Dr Slater and colleagues studied the reaction of 12 premature babies in hospital while having a heel prick test, a technique used to take blood from the feet of infants.

Every newborn baby is given the heel prick within the first couple of days of birth.

The blood samples are used to detect a range of rare life-threatening diseases including cystic fibrosis, sickle cell disease and congenital hypothyroidism.

Some babies cry and grimace when having the heel prick test. But others appear oblivious.

The scientists looked for signs of pain during 33 heel prick tests.

The researchers compared the results of standard techniques of measuring pain – such as changing heart rate, grimacing, flared nostrils and narrowed eyes – with near infra-red spectroscopy brain scans, a technique that detects changes in brain activity.

They found that the scans of parts of the brain involved in handling pain recorded far higher pain levels than the standard tests, they report in the journal Public Library of Science Medicine.

On ten occasions the brain scan revealed that the baby was in pain even though they did not grimace or cry.

Although the study was small, the scientists say doctors could underestimate the pain experienced by babies.

'We really don't know what a baby is feeling when it appears to be in pain,' said Dr Slater. 'But in adults, activity in the same part of the brain is strongly correlated with pain.

'We want to develop better techniques to understand infant pain. Adults can tell each other when they are in pain, but babies cannot.'