Premature babies are repeatedly exposed to painful invasive procedures, yet only 36 per cent of premature babies in Canada get pain relief, according to Celeste Johnston, a McGill University nursing professor and expert in neonatal pain.
These babies "give up" to blunt the pain, Johnston said in an interview at the 13th World Congress on Pain that ends Thursday in Montreal.
"It's similar to depression or learned helplessness," Johnston said of the risk of long-term consequences. "About 20 to 25 per cent of preterm babies in our studies show no response when they have several painful procedures in a row."
Europeans prefer drawing blood from a vein but in North America, preemies get the heel lance.
There are clear Canadian Paediatric Society guidelines for pain relief during such procedures as chest tube insertion and heel lances, Johnston said. Babies should be swaddled, given a pacifier dipped in sucrose, or put in kangaroo care, which is skin-to-skin contact against the mother's chest.
"Why isn't it being done? Well, a lot of us have been studying this," she said. "Is it because they don't believe that the baby is having pain, or it's too much trouble . . . to get the sugar because they don't have enough time? We really don't know. But collaboration among staff predicted better analgesic care."
It was once wrongly believed that newborns do not feel pain. Babies can feel and express pain, Johnston said, noting that since the 1980s, a body of scientific literature emerged to document the many ways that babies communicate their suffering — apart from crying.
A baby in pain grimaces, its eyes squeeze shut, its mouth stretches open and the tongue curls; its oxygen consumption and stress hormones spike, and its tiny heart beats faster.
More recently, scientists found via imaging techniques, that pain activates cortical areas in the preterm newborn brain. The brain images correlated with facial grimaces, Johnston said.
These preemie babies who had many painful interventions during their medical care grow up to be less sensitive to pain as children.
"We thought it would make them more sensitive, so we were surprised," Johnston said. "Mothers of preterm babies have said to us, 'My kid can walk through a glass door and it wouldn't hurt him.' "
But there's a complication. Once they reacted to pain (for example a heat pad), school age children who were premature babies rated their pain higher than full-term children, Johnston said: "There's a difference between pain threshold and pain rating" which may have implications for chronic pain in adults.
Repeated exposure to pain in premature babies who have an extremely plastic and rapidly developing nervous system is critical, Johnston said. The most powerful tool is the kangaroo care. In one video Johnston presented, babies hardly noticed a heel lance when cradled in their mother's arms.