Aim: To explore the variability in pain response in preterm infants across time who received sucrose
during routine heel stick.
Method: Single group, exploratory repeated measures design.
Setting: Two tertiary level neonatal intensive care units (NICU) in Switzerland.
Subjects: Nine preterm infants born between 28 2/7 and 31 4/7 weeks of gestation during their first
14 days of life.
Measurements: Pain was assessed by the Bernese Pain Scale for Neonates (BPSN), the Premature
Infant Pain Profile (PIPP) and the Visual Analogue Scale (VAS). Salivary cortisol was analysed.
Results: 72–94% of the variability was within-subject variability, indicating inconsistency of pain
responses across the 5 heel sticks. Interrater agreement was highest during heel sticks 1–3 and
decreased during heel stick 4 and 5, indicating a possible alteration of pain patterns. No significant
differences in the amount of cortisol could be detected before and after the heel sticks (p = 0.55),
indicating no stress-induced peak after the painful intervention. However, a general gradual decrease
of cortisol levels across time could be detected.