Assessment of Salivary Cortisol Concentration for Procedural Pain Monitoring in Newborns

Background: Despite the major progress in neonatology most infants admitted to the intensive care unit (ICU) are exposed to multiple painful procedures. Observer-independent methods for pain monitoring in newborns remain insufficient. Concentration of salivary cortisol (SC) is a potentially useful and non-invasive method of pain assessment.

Objective: Analysis of the usefulness of SC concentration for procedural pain monitoring in newborns and evaluation of differences in SC between term and premature children.

Methods: 49 infants hospitalized in ICU were assessed for the study. Pain monitoring was performed after 2 procedures: nappy change and blood sampling. The analysis of pain reactions in preterm children was performed after completion of 35 weeks of postmenstrual age. The intensity of pain was assessed using continuous heart rate (HR) and saturation (SpO2) monitoring and SC concentrations. 2 saliva samples were collected for each procedure: before and 20 minutes after procedure’s end.

Results: The study group consisted of 26 (53.06%) term and 23 (46.94%) preterm newborns. The analyzed subgroups did not differ in basal SC (term- 1.7 (1.1-2.6) ng/ml; preterm- 1.85 (1.6- 3.05) ng/ml, p>0.05). There was no significant relationship between basal SC and perinatal factors, however, in the whole group the basal SC was higher in boys than in girls (2.7 (1.3-4.3) ng/ml v.s. 1.65 (1.1-2.1) ng/ml, p=0.04). The SC increased significantly after nappy change in term and preterm children (term- 2.1 (1.1-2.9) ng/ml v.s. 4.1 (2.5-7.1) ng/ml, p=0.04; preterm-1.8 (1.6-2.1) ng/ml v.s. 2.8 (1.9-4.7) ng/ml, p=0.01). The increase of SC was observed also after blood sampling in both subgroups (term- 1.8 (1.3-3.1) ng/ml v.s. 5.1 (3.2-7.6), p= 0.001; preterm- 2.6 (2-3.1) ng/ml v.s. 5.6 (4.3-6.7) ng/ml, p=0.001). There was no significant correlation between changes in SC and vital parameters.

Conclusion: SC is a potentially useful marker for procedural pain monitoring in newborns.