Abstract BACKGROUND: Cardiopulmonary bypass is associated with systemic inflammatory response. Steroids suppress this response, although the therapeutic evidence remains controversial. We hypothesised that intravenous steroids in children undergoing open-heart surgery would decrease inflammation leading to better early post-operative outcomes. We conducted a randomised controlledtrial to evaluate the trends in the levels of immunomodulators and their effects on clinical parameters. OBJECTIVE: To assess the effects of intravenous steroids on early post-operative inflammatory markers and clinical parameters in children undergoing open-heart surgery. MATERIALS AND METHODS: A randomised controlled trial involving 152 patients, from one month up to 18 years of age, who underwent open-heart surgery for congenital heart disease from April 2010-2012 was carried out. Patients were randomised and administered either three scheduled intravenous pulse doses of dexamethasone (1 mg/kg) or placebo. Blood samples were drawn at four time intervals and serum levels of inflammatory cytokines - Interleukin-6, 8, 10, 18, and tumour necrosis factor-alpha - were measured. Clinical parameters were also assessed. RESULTS: Blood cytokine levels were compared between the dexamethasone (n=65) and placebo (n=64) groups. Interleukin-6 levels were lower at 6 and 24 hours post-operatively (p CONCLUSION: Dexamethasone caused quantitative suppression of Interleukin-6 and increased Interleukin-10 activation, contributing to reduced immunopathology, but it did not translate into clinical benefit in the short term.