Evolution of pain management in children holds parallels for animals - December 15, 2001

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By Susan C. Kahler


A V M A      A N I M A L      W E L F A R E      F O R U M

Dr. Benjamin H. LeeFor the past century, pain has been poorly treated in children, began Benjamin H. Lee, MD, MPH, in his presentation. But pain management has come a long way in 20 years, and the advances are attributable in part to parental advocacy.

Dr. Lee is an instructor in anesthesia at Harvard Medical School, an assistant in anesthesia with the Pain Treatment Service, Children's Hospital Boston, and a diplomate of the American Board of Anesthesiology.

Citing studies from the 1970s to the present, Dr. Lee said that inadequate pain management in adults and children is common. Misconceptions about analgesic use and obsessive concern with addiction have been contributing factors.

Children were believed to experience pain more intensely than adults, until the late 19th century, when the fields of developmental embryology and neuroscience were emerging. Infants were considered less capable than adults of experiencing pain.

Charles Darwin, in his work "The Expression of Emotions in Man and Animals," even wrote that expressions of pain in "animals, children, savages, and the insane" should not imply they were aware of pain.

In their 1968 report on pain relief in children, Swafford and Allan stated that only two of 60 children required postoperative pain medication. Eland's study of analgesic use on a pediatric surgery floor found that only 12 of 25 children aged 4 to 8 received any analgesics, even though some had endured such procedures as traumatic foot amputation, heminephrectomy, and treatment of atrial septal defect.

"The case of Jeffrey Lawson changed all that," Dr. Lee said. "He was a 1 pound, 11 ounce neonate who received a patent ductus arteriosus ligation with no anesthesia, only pancuronium, a muscle relaxer. The thinking was that drugs can't be used safely in babies."

Jeffrey died a month later. On reviewing his medical records, his mother discovered he had not received anesthesia for his surgery, contrary to the neonatologist's assurance that he would.

His mother wrote about the surgery and how Jeffrey was conscious throughout it, paralyzed by a curare-type drug. Public outcry came after her account was published in The Washington Post in 1987. This prompted other parents to speak out about their experiences. The practice of administering little or no anesthesia for surgery in premature and critically ill infants became a public issue.

Not only was it believed that their immature nervous systems precluded infants from experiencing pain, Dr. Lee noted, but also they were not thought to have any memory of the pain that might have lasting effects on their behavior and development.

In the 1980s, a series of studies by Aynsley-Green and Anand at the John Radcliffe Hospital in Oxford, England, changed the concept of pain perception and management in infants, Dr. Lee said. Initially they performed a pilot study to prospectively examine stress responses of preterm neonates undergoing PDA ligation. The researchers found that all the patients mounted massive hormonal and metabolic stress responses during surgery. They also found that potent anesthesia resulted in blunting of the stress response and, possibly, improved clinical outcomes.

In a report in the New England Journal of Medicine, Anand and Hickey concluded: "Pain pathways, as well as cortical and subcortical centers necessary for pain perception, are well developed late in gestation, and neurological systems well known to be associated with pain transmission and modulation are also intact and functional."

Dr. Lee described the three routes of pain transmission: peripheral transduction, central modulation, and neurodevelopment of pain.

In a series of experiments, Fitzgerald et al found that spinal cord sensory nerve cells are more excitable in infants than in adults. Infants have a greater, more prolonged response and a larger receptive field.

"The structures for pain perception are present back at birth," Dr. Lee said.

There are potentially long-term consequences of pain in infancy, he went on. Epidemiologic investigations have linked perinatal and neonatal complications with abnormal adult behavior. He qualified those findings, saying that other factors could come into play, such as repetitive pain, sepsis, and maternal separation during a time when families could not freely visit intensive care units.

In 2000, Anand and Scalzo hypothesized that exposure to repetitive pain in infancy could lead to altered pain sensitivity, stress disorders, increased anxiety, and attention deficit hyperactivity disorder.

In studies performed following circumcision without analgesia, researchers found differences in feeding, sleeping, and state control, Dr. Lee noted. Taddio et al, studying pain behavior in boys' response to immunization, found that those who were circumcised displayed more pain behaviors than those who were uncircumcised. This suggests that infants may remember a painful experience, and it alters their response to a subsequent painful stimulus.

Dr. Lee said that several tools have been developed for pain measurement in neonates and infants, and have been tested for validity and reliability. Behavioral and physiologic indicators of pain are also useful.

In a societal context, when the public becomes aware of medical issues, they become social issues, Dr. Lee said. One of the standards for a free society is to protect against unnecessary pain or harm, especially in children and other vulnerable populations. Parents and health care providers have an obligation to protect them, he said.

Advances in scientific research and advocacy by the public have led to changes in pain management, Dr. Lee concluded. Societal pressure has helped propel change more quickly than would have resulted from research alone.

2001 AVMA Animal Welfare Forum - Pain Management