Factors explaining lack of response to heel stick in preterm newborns.

OBJECTIVE

To determine factors explaining lack of response by preterm newborns to heel stick for blood sampling.

DESIGN

A cross-sectional design based on secondary analysis of the control session of a randomized crossover design.

SETTING

Four Level III neonatal intensive-care units of university teaching hospitals.

PARTICIPANTS

120 preterm newborns with an average age of 28 weeks postconceptional age.

INTERVENTION: 24 newborns who showed a "no change" response according the Premature Infant Pain Profile were compared to the remaining 96 newborns who had shown a pain response.

MAIN OUTCOME MEASURES: Age (postconceptional age at birth, postnatal age at study), Apgar score at 5 minutes, severity of illness, sex, race, wake/sleep state, previous study sessions, total number of painful procedures since birth, and time since last painful procedure.

RESULTS

After stepwise logistic regression analysis the variables remaining in the final model that explained the difference between the groups were postnatal age at time of study, postconceptional age at birth, time since last painful procedure, and wake/sleep state.

CONCLUSIONS

Newborns who were younger, asleep, and had undergone a painful event more recently were less likely to demonstrate behavioral and physiologic indicators of pain.