Objectives: To document pain expression characteristics in former preterm infants in the first year of life in whom systematic evaluation and treatment of pain was provided.
Methods: Data on the Modified Behavioral Pain Scale (MBPS), Visual Analogue Scale (VAS, crying time and heart rate were collected during immunization. The effect of clinical characteristics {postconception and gestational age [PCA], surgery, ventilation, fentanyl, length of stay (LOS)} on bio-behavioral parameters was evaluated.
Results: 121 procedures were recorded in 49 infants. GA was 28 (25-32) weeks. PCA was 60 (34-90) weeks. Median MBPS was 8 (2-10), median crying time 44 (0-112) s. Median pre-procedural heart rate was 144 (103-201) and increased to 184 (147-220) afterwards, resulting in a relative increase of 29 (5-99)%. Median VAS score was 7 (1-10). Significant correlations of PCA with pre-procedural heart rate (r=-0.36) and with relative increase in heart rate (r=0.33) were identified. A correlation of LOS on crying time (r=0.37) was observed.
Conclusions: Correlations of PCA with pre-procedural and relative increase in heart rate reflect the maturational decrease in heart rate. LOS had an effect on pain expression, potentially reflecting the impact of cumulative 'minor' procedural pain.