The PRE-OP ENERGY Trial

PRE-OP ENERGY is a single centre, unblinded, parallel group, randomised controlled trial of a pre-operative high energy diet, versus a control group receiving standard care. The trial will test a number of specific hypotheses: 1. A pre-surgery high energy diet will protect against post-cardiac surgery organ failure by altering the pre-surgery cardiometabolic state, a process referred to as 'metabolic preconditioning'. 2. The effects of the trial intervention will not be attributable to changes in frailty, activity or baseline organ dysfunction. 3. The trial intervention will not result in long-term adverse changes in cardiometabolic status. 4. Metabolic preconditioning will confer protection against post-cardiac surgery kidney injury by increasing the expression of genes that promote renal tubular homeostasis. 5. Metabolic preconditioning will confer protection against post-cardiac surgery myocardial injury by increasing the expression of genes that promote myocardial mitochondrial homeostasis via effects on chromatin histone deacetylation. 6. Metabolic preconditioning will confer protection against post-cardiac surgery endothelial dysfunction by increasing the expression of genes that promote endothelial homeostasis.