The neuroendocrine stress response and severity of acute respiratory syncytial virus bronchiolitis in infancy

Objective: Neuroendocrine hormones have profound effects on the immune system. The immune response is a major factor in the pathogenesis of acute respiratory syncytial virus (RSV) infection. We hypothesised that there is a relationship between the neuroendocrine response in acute RSV infection, the severity of illness, and the degree of lymphopenia. Design: Prospective, non-randomised cohort study of infants hospitalised for RSV infection requiring mechanical ventilation or managed conservatively. The study assessed the effect of age, gender, birth gestation. and severity of illness on stress hormone profile and its relationship to lymphocyte count. Setting: Regional Paediatric Intensive Care Unit (PICU) and children's wards. Patients: Thirty-two consecutive infants with RSV infection were enrolled, of which thirteen were mechanically ventilated on PICU (study subjects) and nineteen treated on the ward (comparison group). Twenty-three children (72%) returned for follow-up. Measurements and main results: A specific neuroendocrine profile was found in PICU patients compared to ward patients (Wilks Lambda=0.36, F=9.05, P=.03). PICU patients had significantly higher prolactin and growth hormone, and significantly lower leptin and IGF-1. Cortisol levels were the same. PICU patients were more lymphopenic compared to ward patients (P=.0001). On multiple regression analysis, prolactin and leptin levels accounted for 57% of the variation in lymphocyte count. Conclusions: Whereas the effect of intensive care (mechanical ventilation and medication) could not be controlled for, our results suggest that there is an association between the neuroendocrine hormone response, severity of illness and degree of lymphopenia.