The Safety and Efficacy of Perioperative Dexmedetomidine in Cardiac Surgery Patients - A Pilot Trial

Cardiac surgery is one of the most common complex operations conducted on millions of patients worldwide every year. Advances in bypass technology and surgical techniques improved mortality and outcomes after cardiac surgery. Patients presenting to cardiac surgery are older, suffer multiple comorbidity and likely to undergo more complex operations. Therefore, significant morbidity continues to be associated with cardiac surgery including acute kidney injury and failure, neurological injury such as stroke, delirium or cognitive dysfunction, cardiac failure and arrhythmias such as atrial fibrillation and respiratory failure. These complications, in combination or individually, leads to increased hospital stay and increased disability and functional dependence. Dexmedetomidine is a strong sympatholytic agent that has been used as a sedative and adjunct for procedural sedation. Animal models of global hypoxic brain injury, myocardial ischaemia reperfusion and contrast induced kidney injury showed potential protective effects, possibly due to reduced apoptosis and inflammatory response. A Cochrane systematic review concluded that the perioperative use of Alpha2 agonist reduced mortality and myocardial ischaemia with most pronounced effect seen in vascular and cardiac surgery. In the context of cardiac surgery, randomised trials of dexmedetomidine has been shown to reduce delirium, acute kidney injury and postoperative ventilation time. Retrospective propensity score analysis suggested that dexmedetomidine reduced hospital and 1 year mortality in patients undergoing cardiac surgery. In concert, these studies suggest that perioperative use of dexmedetomidine may reduce cardiac surgery associated complications, including mortality and likely to days home and disability free following high risk cardiac surgery. Aims: 1. Assess the safety and efficacy of perioperative dexmedetomidine in high risk cardiac surgery. 2. Inform the design and conduct of a phase III multicentre study on the clinical effectiveness of dexmedetomidine in cardiac surgery Design: Multicentre Single blind placebo controlled RCT Population and sample size: 80 patients in 4 sites Inclusion criteria: consenting adult patients undergoing on bypass cardiac surgery with 1. Combined surgery (CABG + valve) or (valve) or aortic arch surgery OR 2. Chronic Kidney disease class III and IV with estimated GFR 1559 mls/min/1.72m2. Intervention: Dexmedetomidine infusion at 0.7 mcg/kg/hr will commence at the induction of anaesthesia and be continued throughout the surgery. Dose will be reduced by 0.4 mcg/kg/hr at skin closure and continue until clinically not required. Concomitant intervention: Standard anaesthesia. Primary outcomes: A composite outcome of number of days home, alive and disability free at 28 days following surgery will be the primary study outcome.