Effects of Nutritional Preconditioning on the Patient's Outcomes After Surgery

Malnutrition is a serious problem in patients undergoing major surgeries and has a direct association with increased morbidity, mortality, length of stay (LOS), increased readmissions and cost of care. Studies suggest several advantages of supplementation with protein or specific amino acids in malnourished patients. Dietary leucine or its metabolite β-hydroxy β-methylbutyrate (HMB) can improve skeletal muscle mass and function by increasing transcriptional level of protein synthase, while other high protein or amino acids like Glutamine or Arginine supplements only provide protein-amino acids pool for patients while body's preferred fuel during metabolic stress is endogens protein, rather than exogenous diet. In this study the investigators seek to achieve two distinct goals: 1. Determine the patients' nutritional status before and after major surgeries by baseline and subsequent nutritional assessments, according to ASPEN's criteria. In addition, the investigators were going to use indirect calorimetry to determine the Resting Energy Expenditure (REE) in different phases of pre- and postoperative periods. The investigators also propose to compare different serum protein markers and their ratios in order to correlate them with ASPEN's criteria for nutritional status quantification. In Summary, three discrete tools including ASPEN's criteria, indirect calorimetry, and serum biomarkers are going to be used in conjunction with each other to delineate the patients' nutritional status in various pre- and post-operative periods. 2. Patients undergoing major surgeries were supplemented with high protein with ß-hydroxy ß-methylbutyrate (HMB) (Ensure, Envile) or HMB only as a control, in order to improve their nutritional status and improve postoperative outcomes. The investigators looked for depict meaningful improvements in surgical outcomes by nutritional supplementation with or without HMB.