Pain Measurement Tools May Be Too Blunt for Infants

June 26, 2008

Behavioral assessment may not give an accurate picture of pain in infants because they may process pain at the cortical level and not exhibit any behavioral changes, according to research published in the June issue of PLoS Medicine.

THURSDAY, June 26 (HealthDay News) -- Behavioral assessment may not give an accurate picture of pain in infants because they may process pain at the cortical level and not exhibit any behavioral changes, according to research published in the June issue of PLoS Medicine.

Rebeccah Slater, Ph.D., of University College London in the United Kingdom, and colleagues measured hemodynamic activity in 12 infants born at 24 to 34 weeks' gestation who were given a total of 33 clinically required heel lances. The investigators compared cortical activity with behavioral signs of experiencing pain, such as changes in facial expression.

Using the premature infant pain profile score to measure behavioral changes, there was a high degree of correlation with the measures of cortical activity, with the best correlation being changes in facial expression. However, some infants registered cortical activity without any indication from facial expression of feeling pain, the researchers report.

"The absence of facial activity may simply be due to immature motor circuitry failing to produce synchronized and coordinated muscle contraction, or it may indicate a true absence of emotion," the authors write. "Since nociceptive activity is clearly transmitted to the brain on these occasions, we suggest that, either way, the infants may not actually be pain free. As a result, pain assessment based on behavioral tools alone should be interpreted with caution as they could underestimate the total pain response."

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