Assessment of salivary cortisol concentrations for procedural pain monitoring in newborns

Abstract

Objectives: The study aimed to evaluate the usefulness of salivary cortisol (SC) for the assessment of procedural pain intensity in preterm and term newborns.

Methods: Three groups of neonates (term, 37⁰-41⁶ weeks; moderate to late preterm, 32⁰-36⁶; and very preterm, <32⁰) hospitalized in neonatal intensive care unit were assessed for the study. Response to nappy change, lung ultrasound (LUS), and blood sampling was analyzed. The intensity of pain was evaluated using continuous heart rate and blood oxygen saturation (SpO₂) monitoring, Neonatal Infant Pain Scale (NIPS), and SC concentrations. Saliva samples were collected before and 20 min after the procedure's end.

Results: Seventy-one infants were examined: 30 term, 21 moderate to late preterm, and 20 very preterm. SC has increased significantly in response to nappy change only in very preterm newborns (2.13 ng/mL [1.55-3.68] vs. 2.84 ng/mL [1.93-9.06], p = 0.01). LUS did not affect concentrations of SC in any group. Significant increase in SC was observed after blood sampling in term and very preterm infants (2.2 ng/mL [1.45-2.92] vs. 4.29 ng/mL [3.88-5.73], p = 0.002, and 1.88 ng/mL [1.47-4.13] vs. 5.3 ng/mL [3.42-8.02], p = 0.002, respectively). A significant correlation between values of SC increase and NIPS scores was found (Spearman's rank correlation coefficient [r_s] = 0.31, p = 0.001).

Conclusions: We observed the increase in SC concentrations in response to painful stimulus. The presence of a correlation between NIPS scores and SC increase suggests that SC can be used as an objective parameter to assess pain in neonates.

Keywords: Neonatal Infant Pain Scale; newborn; pain; salivary cortisol.