Premature babies feel pain but don't show it

Brain scans of premature babies undergoing a simple medical procedure have revealed though they may appear to be pain free, they are experiencing pain.

In a study conducted by researchers at University College London researchers found changes in brain oxygen levels which is a response to pain, did not match other signs and while some babies cry and grimace when having the heel prick test, others appear oblivious.

Previous research has suggested that babies who experience a lot of pain in the first few months of life can develop extreme sensitivity to pain as they get older.

The researchers suggest that commonly used scales to rate pain in babies may produce misleadingly low scores.

Lead researcher Dr. Rebeccah Slater says the ability of premature babies to feel pain has been debatable in medicine as well as the level of painkiller needed to prevent pain.

Dr. Slater says some babies do not cry out in response to procedures such as the "heel prick" test, carried out regularly in neonatal units to obtain a blood sample.

Every newborn baby is given the heel prick within the first couple of days of birth and the blood samples are used to detect a range of rare life-threatening diseases including cystic fibrosis, sickle cell disease and congenital hypothyroidism.

All doctors and nurses have to rely on as an indication of pain are facial changes, and disturbed sleep patterns, but Dr. Slater says there are subtle changes in heart rate and blood oxygen saturation which indicate whether an infant is in pain.

The researchers recorded responses to the heel prick test in 12 babies while also measuring brain changes in an area of the brain called the somatosensory cortex - the changes in oxygen levels in certain areas of the brain are believed to be a byproduct of nerve activity in reaction to pain.

The researchers say while, overall, the relationship between the brain responses and the other changes was close, in some of the babies, there was a brain response without any other physical sign which raises concern about the tools normally used by doctors to establish whether a baby is feeling pain.

Dr. Slater says infants may appear to be pain free, but may, according to brain activity measurements, still be experiencing pain.

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

The study is published in the Public Library of Science journal.