Salivary biomarkers may measure stress responses in critically ill children

Objective: Measurement of salivary biomarkers can provide important information regarding hypothalamic-pituitary-adrenal axis activity both under normal conditions as well as in response to psychological or physical stress. Our aim was to correlate salivary stress markers, such as cortisol, -amylase and immunoglobulin A, with the Pediatric Risk Index Score of Mortality, underlying disease (pathologic, trauma and postoperative), need for mechanical ventilation/sedation and time lag between onset of illness and admission in children admitted in the pediatric intensive care unit. Methods: We enrolled 79 pediatric intensive care unit patients (2-14years) over a 2-year period, which satisfy the including criteria, but finally salivary biomarkers were evaluated in 65 patients. Saliva samples were collected within 24h of admission at 8a.m., 2p.m. and 8p.m. to examine potential disruption of circadian rhythm. Results: Overall, the salivary biomarkers were increased; specifically, median values were (a) cortisol at 8a.m.: 50.04nmol/L, 2p.m.: 30.69nmol/L and 8p.m.: 247.12nmol/L; (b) -amylase: at 8a.m.: 22.567U/L; 2p.m.: 22.702U/L and 8p.m.: 21.484U/L and (c) IgA at 8a.m.: 95.10mg/dL, 2p.m.: 88.55mg/dL and 8p.m.: 80.80mg/dL. Significantly higher levels were demonstrated in children younger than 6years and those with Pediatric Risk Index Score of Mortality 8 upon admission. Disturbances in circadian rhythm were observed. Cortisol circadian rhythm disturbance was observed only in children with Pediatric Risk Index Score of Mortality score 8 upon admission while maintaining normal -amylase circadian rhythm, which was associated with less than 3days hospitalization in pediatric intensive care unit. No daily variance in IgA was observed. Conclusion: Salivary biomarkers may serve, in critically ill children, as a sensitive, non-invasive method, important for the early recognition of those at high risk and guiding intervention, before clinical deterioration, promoting the quality of health care in pediatric population.