Preemie Pain May Have Lasting Effect, Study Says
WASHINGTON — For years, doctors operated on premature babies without anesthesia in the belief that even if the infants felt the pain, they would not remember it. New research with rats suggests that the body does remember the pain and is forever changed.
A study using newborn rats at the National Institutes of Health found that painful trauma that mimics medical procedures commonly performed on premature infants caused the rats to become much more sensitive to pain as they grew older.
The reason is that pain causes the developing nervous system of the very young to grow more nerve cells that carry the sensation of pain to the brain, NIH researcher M.A. Ruda said.
“We found that there are more nerve endings that fire and transmit the [pain] information,” said Ruda, the first author of a study appearing Friday in the journal Science. “These animals later were more sensitive and had a greater response to pain.”
Ruda said the study only suggests what may happen in premature infants.
“This is animal research so one has to be cautious in extrapolating to humans,” she said. “But we use these animals as models of pain, and they have been very valid for predicting the responses” in humans. The study is part of a continuing effort by medical science to understand how and when the nervous system develops and how the growth of nerve tissue is affected by stimulation, such as pain. Such research has a direct bearing on efforts to save and improve the lives of infants born prematurely. Survival of babies born up to 15 weeks premature is now not unusual, but it takes a major medical effort and many painful procedures, including countless needle sticks, breathing tubes and even surgery.
Just how much pain such babies feel has been uncertain, said Dr. Patricia A. McGrath, a pain researcher and professor of pediatrics at the University of Western Ontario, who was not a member of the Ruda research team.
Ten years ago, she said, there was a belief that “the pain system in premature babies was not developed and these infants would really not feel as much pain.”
More important, McGrath said, doctors had concerns that premature infants given powerful anesthetics “would not be able to clear the drug as well as older infants.” The choice sometimes was between skipping anesthesia during lifesaving surgery or passing on any therapy. Most doctors chose life.But Ruda said the study in rats suggests there is a lasting effect, a change in the nervous system caused by the trauma. If this conclusion is the same in humans, she said, it could mean that premature infants who endured pain of major medical therapies may have a sharpened sensitivity to pain all their lives.
Dr. Jonelle C. Rowe, an NIH doctor who specializes in treating premature babies, said that although some babies in the past may have had surgery without anesthesia, it was rare. But she confirmed that even now some procedures that require pain killers in adults--such as inserting a breathing tube--are done on premature babies without anesthesia.
