Steroids In caRdiac Surgery Trial (SIRS Trial)

Cardiopulmonary bypass (CPB) is a commonly performed surgical procedure with over 500,000 per year in North America. CPB initiates a systemic inflammatory response characterized by both cell and protein activation. Platelets, neutrophils, monocytes, macrophages, coagulation, fibrinolytic, and kallikrein cascades all take part in what results in increased endothelial permeability, vascular, and parenchymal damage. These inflammatory pathways facilitate development of post-operative complications including thrombosis, myocardial injury and infarction, respiratory failure, renal and neurological dysfunction, bleeding disorders, altered liver function and ultimately, multiple organ failure.

In an attempt to minimize the deleterious effects of CPB, investigators have tested a variety of strategies in cardiac surgery ranging from the complete avoidance of CPB, to the use of biocompatible circuits and pharmacologic agents to abrogate the systemic response. Investigators have consistently demonstrated the efficacy of steroids as the most potent anti-inflammatory agent for use during CPB. In fact, from the available evidence, the 2004 AHA guidelines for coronary artery bypass grafting (CABG) "support liberal prophylactic use in patients undergoing extracorporeal circulation". However, the trials that do exist within this literature are focused on biochemical endpoints and are insufficiently powered to make conclusions on hard clinical endpoints. Our pilot RCT, SIRS I, demonstrated the efficacy of a low dose steroid protocol in the suppression of this inflammatory cascade. We hypothesize that this low dose protocol will yield clinical benefit while avoiding the potential adverse effects of steroids which are known to be dose dependent.

The primary aim of the SIRS trial is to determine if perioperative pulse dose Methylprednisolone results in improved early survival and less myocardial infarction in cardiac surgery requiring CPB. Additional secondary aims of the SIRS trial are to determine the effect of steroids on other clinical outcomes including length of stay, new onset atrial fibrillation, transfusion requirements, infectious, wound, and gastrointestinal complications.

The design of the SIRS trial is a prospective multicentre international double-blind placebo controlled randomized clinical trial. The sample size of 7500 patients will have 80% to 90% power to detect a 20-30% RRR for the primary outcome with an α=0.05 (two-sided), anticipating a 6% rate of death in the control arm. Our aim is to have 85 international centers participate which, recruiting at 5 patients per month, would complete recruitment in 36 months. This will be a large trial with a simple design and objective outcomes.

A sub-group of patients will be enrolled in a renal sub-study. This sub-study will determine if the risk of acute kidney injury is lower in patients treated with intravenous steroid versus placebo, if steroids lead to better preservation of kidney function six months after cardiac surgery, and whether the impact of steroid exposure differs in patients with and without pre-operative chronic kidney disease.