A New Way To Measure Pain in Infants

Infant pain

A simple electroencephalogram recording provides an objective measure of pain in infants. Image credit: Department of Paediatrics, Medical Science Division, University of Oxford.

In the first week of life, a newborn undergoes an average of 11 painful procedures every day, such as a blood draw, yet only a third of these babies receive any form of pain medication. But because babies can’t talk, it’s challenging to know when they are in pain or if a pain reliever is working. Now, a team of researchers has identified a brain signal that may help doctors determine whether or not a baby is in pain.

A team led by Rebeccah Slater at the University of Oxford, UK, used a simple electroencephalogram (EEG) recording, which measures electrical activity in the brain, to identify a pattern of brain activity present when newborns underwent a standard heel lance; this is a procedure in which a small blood sample is obtained from a prick of the heel. The researchers then showed that this pattern of activity could be used to test how well a local anesthetic applied to the skin relived pain.

The work was published online May 3 in the journal Science Translational Medicine.

Without language, how do you know if a baby is in pain?
Since babies can’t talk, doctors must rely on surrogate measures, such as changes in facial expressions or heart rate, or the presence of crying, to know if they are experiencing pain. But in fact it is difficult to make that determination using this approach.

“Clearly these behaviors are not specific to pain,” explained Slater. “They can occur for other reasons, like when a baby is hungry.”

So, Slater and her colleagues asked whether they could overcome this challenge by looking at the brain. “Pain is an experience that manifests in the brain so in the absence of language, one way of trying to understand it is by looking at what’s happening within the brain,” said Slater.

To do this, the team attached eight EEG electrodes to the scalp of 18 infants who were scheduled to receive a clinically required heel lance, a procedure known to be painful. Within milliseconds, a noticeable burst of activity could be seen at a single electrode sitting at the very top of the head.

Critically, the signal was absent when the researchers exposed the babies to non-painful touch of the heel or to non-painful sounds and sights. This showed that the signal was specific to painful stimuli.

Importantly, this pattern of brain activity can be used in future studies of infant pain, since doctors and researchers can compare the pattern of brain activity they may observe to that identified in the new study.

Slater’s team also asked if they could see the brain signal in infants born prematurely. Indeed, the pattern they saw in the full-term infants was also present in preterm babies undergoing a heel lance.

Finally, a topical pain reliever applied right before a painful procedure reduced the magnitude of the EEG signal. This suggests that the new approach may prove useful in the clinic to confirm whether other pain medications are working or not.

In fact, the researchers are now testing this idea in a clinical trial. Here, they are studying whether morphine reduces the pattern of brain activity seen in the current study during an eye exam that’s critical for preterm infants but is considered to be painful. The trial, called Procedural Pain in Premature Infants (Poppi), is anticipated to be completed in the Fall of 2018.

To read about the research in more detail, see the related Pain Research Forum news story here.

Nathan Fried is a postdoctoral fellow at the University of Pennsylvania, Philadelphia, US.