Research sheds new light on how babies feel and respond to pain

You’re in hospital and you need to have a blood test: What do you think would reduce your pain?

  • Sucrose (sugar water)
  • Painkillers

You probably went with option 2. But in babies option 1 is often prescribed.

It is difficult to test whether painkillers work for very young children and there is often uncertainty about the best dose to give. But if Professor Rebeccah Slater and her research team at Oxford are successful we may find alternative ways to measure pain in babies and may eventually be able to offer babies some better options to soothe their pain.

The research, published in Current Biology, looks at how babies who have been born prematurely respond when a routine blood sample is taken from the heel of their foot.

Premature babies routinely have to undergo as many as ten painful procedures a day. The researchers – with permission of the babies’ parents – monitored a selection of premature babies’ brain activity and reflexes during some of these routine procedures.

“The youngest babies have disorganised and exaggerated motor responses when painful procedures are performed,” explained Dr Caroline Hartley, one of the researchers working on the study. “For example, they might pull away both feet even when the blood test is performed on just one foot.”

“As they get older, these reflex movements become quicker, shorter and smaller. They respond faster but don’t pull away as much. However, you cannot directly infer how much pain a baby is experiencing from these responses – for example a premature baby can withdraw both their legs even in response to a light touch.”

In the study the babies’ brain activity was also measured by placing electrodes on their heads prior to the blood tests.

Dr Hartley said: “The younger babies showed brain activity that was not specific to pain – a bright light or loud noise would cause much the same pattern of activity. As they got older, brain activity matured and the evoked brain activity increased.”

“Considering both measures together, we found that older babies with more mature brain activity had more refined reflexes.”

This study suggests that top-down inhibitory mechanisms may begin to emerge during early infancy.

As adults, we may instinctively stop ourselves from pulling our hand away from the handle of a hot pan if the alternative would be to tip boiling water everywhere, a potentially more dangerous result: that’s an example of top down inhibition.

The observation that, as the babies get older, more mature brain activity is related to more refined reflex activity, suggests that these inhibitory mechanisms may begin to play a role.

“Doctors and nurses rely on behavioural observation to make judgements about pain in babies,” explained Professor Slater. “Our results show that the movements of a premature baby in response to a painful procedure may not be proportionate to the amount of information that is being transmitted to the brain.”

“This is critical if we are trying to develop effective pain relief for babies. If we understand better how the immature brain processes information about pain, we may be able to use these patterns of brain activity to see whether different types of pain relief are effective in babies.”

Via University of Oxford Science Blog