Heel lancing in term new-born infants: an evaluation of pain by frequency domain analysis of heart rate variability

The aim of the investigation was to assess pain by frequency domain analysi s of heart rate variability (HRV) during a routine heel lancing procedure i n term new-born infants. Beat-to-beat heart rate (HR) was recorded in 23 he althy new-born infants on the maternity ward during blood sampling for neon atal screening. A sham heel prick prior to the sharp lancing procedure was performed randomly in half of the infants. Spectral analysis of HRV was ass essed for each of the following sequences: (1) baseline (2) sham heel prick (3) sharp heel prick and (3) squeezing the heel for blood sampling. The re sponse to the sham prick did not differ significantly from the sharp prick. Compared with the baseline, sharp lancing gave rise to minor increases in HR and variability in the low frequency band of the spectral analysis. A cl ear stress response was provoked when the heel was squeezed for blood sampl ing, indicated by an increased HR and a decreased spectral power in the hig h frequency band (i.e. lower vagal tone). The different stress responses du ring the lancing and the squeezing of the heel were clearly illustrated whe n principal component analysis was applied and the vectors for the changes in HR and spectral pattern were indicated. In conclusion, the squeezing of the hed is the most stressful event during the heel prick procedure. (C) 19 99 International Association for the Study of Pain. Published by Elsevier S cience B.V.