The effect of nutrition in cardiac surgical patients on heart function.

Rationale: 
Malnutrition is very common in patients undergoing cardiac surgery as well as other types of surgery. For example, in a population of cardiac and abdominal surgical patients, respectively 9.1% and 44% was malnourished. Malnutrition can change myocardial substrate utilization which can induce adverse effects on myocardial metabolism. Interestingly, malnutrition is an underlying risk factor for the perioperative cardiac complications seen in patients undergoing non-cardiac surgery. Therefore, by optimizing nutritional status of (cardiac) surgical patients, cardiac metabolism and function might be improved. This can be done by administration of enteral or parenteral feeding. 

Objective:
Our primary objective is to evaluate the effect of perioperative enteral and peripheral parenteral nutrition on amino acid profile and cardiomyocytes functioning of cardiac surgical patients. Our secondary objective is to study the effect of (par)enteral nutrition on cardiac perfusion, and fatty acid and glucose metabolism. We hypothesize that there is a disturbed amino acids profile in the cardiac surgical patient and that nutrition during surgery will normalize this profile with a subsequent improvement in cardiomyocytes functioning by histology, and in cardiac perfusion and metabolism. 

Study design: 
This proof-of-concept will be investigated in a randomized controlled intervention study.

Study population: 
Our research population will consist of 48 patients undergoing cardiac surgery for coronary artery bypass grafting (CABG) at the department of cardio-thoracic surgery at the Academic Medical Center University of Amsterdam. 

Intervention: 
Our patients will be given enteral nutrition (n=16), peripheral parenteral nutrition (n=16) or a saline solution (control) (n=16) at least three days before, during, and one day after CABG. Both enteral and parenteral nutrition are mixtures of amino acids, glucose, lipids, vitamins, and minerals. 

Main study parameters/endpoints: 
We will illustrate the effect of nutrition by differences in amino acids concentrations in blood plasma and cardiac tissue, and in cardiomyocytes functioning between the (par)enteral and control group. In addition, differences in cardiac perfusion, and fatty acid and glucose metabolism between the (par)enteral and control group will be evaluated by myocardial scintigraphy with the tracer technium99m-tetrofosmine (99mTc-tetrofosmine), by myocardial scintigraphy with beta-methyl-p-[123I]-iodophenyl-pentadecanoic acid (123IBMIPP), and by using positron emission tomography (PET) with the tracer F18-fluorodeoxy-glucose (18FFDG) respectively.

We hypothesize that there is a disturbed amino acids profile in the cardiac surgical patient and that nutrition during surgery will normalize this profile with a subsequent improvement in cardiomyocytes functioning by histology, and in cardiac perfusion and metabolism.

Blood samples will be taken before, during and after surgery. Cardiac tissue samples will be collected during surgery. Myocardial scintigraphy, and a PET-scan will be performed at baseline and 3 weeks after surgery.

Our patients will be given enteral nutrition (n=16), peripheral parenteral nutrition (n=16) or a saline solution (control) (n=16) at least three days before, during, and one day after CABG. Both enteral and parenteral nutrition are mixtures of amino acids, glucose, lipids, vitamins, and minerals.