Assessment in nonverbal populations (infants, mentally impaired, etc.): Pain responses in neonates at risk for neurologic impairment

Abstract

The aim was to compare the behavioral and physiological pain responses in neonates at high, moderate and low risk for neurologic impairment (NI). A prospective observational cohort study was undertaken with 142 neonates (GA >25- 40 weeks) at high (cohort A, n=53), moderate (cohort B, n=39) and low (cohort C, n=50) risk for NI from 3 tertiary level NICUs in Canada. Behavioural and physiological responses were recorded during a routine heel lance. Cohort A infants had higher birth weights, increased maturity, and lower Apgar scores than other groups. Infants in Cohort B had significantly higher SNAP:IIJ severity of illness scores. There was a significant cohort by phase interaction for total facial expression(F(6,438) = 3.58 ,p=.002), and individual facial actions including eye squeeze, nasal labial furrow, vertical stretched mouth and taught tongue. Cohort C had the most facial expression following heel lance. A significant within-subject phase effect was found across groups with increased maximum heart rate (F(3,431) = 58.1 , p =.001), minimum heart rate (F(3,431) =78.7 , p=.001), maximum 02 (F(3,425) = 47.6 , p=.001), minimum 02 (F(3,425) = 12.2 , p=.001) following heel lance. Cohort B had higher minimum (F(2,65) =8.9, p=.001), maximum (F(2,64) =4.2 , p=.02) and mean (F(2,65) = 8.8 , p =.001) fundamental cry frequencies. There was a significant phase effect for the low frequency/high frequency Heart Rate Variability (HRV) ratio(F(2,204) =6.47 , p=.001) with the greatest decrease in Cohort A. There were also significant cohort by phase interactions for low and high frequency HRV following heel lance. Infants at the highest risk for NI exhibited the least facial expression and change in physiologic indicators, but greatest decrease in HRV ratio. Infants with moderate risk for NI and highest severity of illness had the highest pitched cries.