Hepatic Transaminase Levels Reflect Disease Severity in children with severe Respiratory Syncytial Virus (RSV) Bronchiolitis C. Fulton, K. Thorburn, Alder Hey Children’s Hospital, Liverpool C. King, D. Ramaneswaran, A.Abdulaziz, P.McNamara Liverpool University INTRODUCTION Elevated hepatic transaminases are recognised in some children requiring mechanical ventilation on paediatric intensive care units (PICU) for RSV bronchiolitis – thought to be consequential to hepatic congestion or ischaemia due to right heart strain, itself secondary to parenchymal lung disease and/or pulmonary hypertension. It has been suggested that children with raised transaminases have increased disease severity. OBJECTIVES The aim of this project was to compare disease severity as judged by duration of ventilation, length of PICU admission, respiratory indices and mortality in children mechanically ventilated for RSV bronchiolitis with and without elevated hepatic transaminases. METHODOLOGY Ventilated children with RSV bronchiolitis on PICU at Alder Hey Children’s Hospital between October 2002 and March 2013, covering 11 RSV seasons, were included in the study. All participants had their liver transaminase levels (AST and ALT) taken daily whilst on PICU. Levels were considered elevated when ALT >36u/L and AST >58u/L. Markers of severity were: mortality, duration of ventilation, length of admission, oxygen index and ventilation index. Children with co-morbidity were excluded, removing it as a confounding factor for increased hepatic transaminase levels. A p-value <0.05 was considered statistically significant, all p-values were two tailed. RESULTS Table 1: Baseline characteristics of children ventilated with RSV bronchiolitis with and without elevated transaminase levels (n=330)  – number or mean (standard deviation): 556 children with RSV bronchiolitis were ventilated over the 11 RSV seasons (no co-morbidities n=330, co-morbidities 226 – therefore excluded) 144 (44%) of the 330 children with no co-morbidities had elevated transaminase levels. The characteristics of this no co-morbidity group are shown in table 1. The values and chronology of the transaminase levels are shown in figures 1-3. All of the deaths were in infants <1 years of age. Duration of ventilation, length of PICU admission, worst oxygen index and worst ventilation index were statistically higher in the subgroup with elevated transaminases. a Fishers exact test;  b Mann-Whitney-U test. IQR = interquartile range. Oxygen index (OI) = mean airways pressure X FiO2/PaO2 – worst OI within first 72 hours of PICU admission. Ventilation index (VI) = respiratory rate X PaCO2 X peak inspiratory pressure/1000 – worst VI within first 72 hours of PICU admission. CONCLUSION RSV-positive bronchiolitis was more severe in children who were admitted with elevated hepatic transaminase levels. This study does show that elevated transaminase levels could be used as a predictor for disease severity in RSV bronchiolitis. DISCUSSION In the patient group with elevated transaminase levels there was a transient trend that peaked between days 2-4. The transient effect suggests that there was no lasting damage/injury to the liver. Possible explanations for the raised hepatic transaminases are: RSV-induced hepatitis, right ventricular heart strain causing hepatic congestion, ischaemic hepatitis and hypoxic hepatitis. Right ventricular heart strain causing hepatic congestion or ischaemic hepatitis seem the most likely aetiology for the elevated hepatic transaminases. crawf@doctors.net.uk