"This was the first study to look at anticipatory pain responses in newborns. This research confirmed anecdotal reports that infants become hypersensitive to pain and learn to anticipate pain as a result of cumulative exposures to pain," said Dr. Taddio, the study's principal investigator, an HSC pharmacist and associate scientist, and an assistant professor of Pharmacy at the University of Toronto.
"Many newborn infants undergo painful, invasive procedures after delivery for medical reasons and it is important for us to understand how they react to pain, and look at ways to decrease their pain, " added Dr. Taddio.
In the study, infants who received repeated painful procedures (heel lances) over the first 24-36 hours of life were compared with a control group of infants. The heel lances were necessary to monitor the infants' blood sugar levels as they were born to mothers with diabetes and were exposed to higher levels of glucose in utero relative to infants of non-diabetic mothers. In order to counteract the high levels of glucose, the infants produce more insulin. After birth, their blood glucose levels may fall rapidly below normal values due to relative overproduction of insulin. Following standard clinical guidelines, blood was taken from the infants' heels every two to four hours after birth to monitor glucose concentrations until the infants were able to readjust their insulin production (an average of 10 heel lances per infant).
All infants in the study were healthy and on the postnatal ward with their mothers. The infants in the control group were matched to those of diabetic mothers on birth characteristics such as weight, gestational age, gender and type of delivery.
After 24 hours of life, a blood sample was taken from the hands of all infants (venipuncture) as part of the routine newborn screening test. The babies who had been poked repeatedly with the heel lances had an increased pain response (facial grimacing, crying) compared with the infants who had not been exposed to the repeated painful procedures. They demonstrated behaviours of pain even before they were actually poked for the blood collection, when the nurse wiped their hand with alcohol in preparation for the venipuncture. This response suggests that they learned to anticipate pain. They also experienced a bigger response to the venipuncture itself.
Dr. Taddio collaborated on this study with Dr. Vibhuti Shah, neonatologist at Mount Sinai Hospital, Dr. Cheryl Gilbert-MacLeod, psychologist at IWK Health Centre, and Dr. Joel Katz, senior scientist in the Department of Anaesthesia at Toronto General Hospital and Mount Sinai Hospital, and holder of a Canada Research Chair in Health Psychology, York University. The infants in the study were at Sunnybrook and Women's College Health Sciences Centre, Women's College Campus, in Toronto. This research was supported by The Hospital for Sick Children Foundation, and the Canadian Institutes of Health Research through an Investigator Award to Dr. Katz.
The Hospital for Sick Children, affiliated with the University of Toronto, is the largest paediatric academic health science centre in Canada and one of the largest in the world. Its mission is to provide the best in family-centred, compassionate care, to lead in scientific and clinical advancement, and to prepare the next generation of leaders in child health. For more information, please visit www.sickkids.ca.
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Laura Greer, Public Affairs
The Hospital for Sick Children