Whey Protein-based Enteral Nutrition Support to Improve Protein Economy in Surgical Patients

A prospective, randomized and controlled study is proposed to establish whether an enteral nutrition support regimen based on pressurized whey protein and glucose improves the postoperative utilization of amino acid substrates compared to a drink based on glucose alone. The kinetics of protein metabolism (protein breakdown, protein synthesis and amino acid oxidation) will be investigated using stable isotope methodology before and after surgery in patients undergoing colon resection. Stable isotope infusions will be conducted one week before surgery and on the second postoperative day for two hours in the fasted state and for four hours while sipping the enteral nutrition support regimen. Patients will consume one of two enteral nutrition support regimens consisting of a drink containing either pressurized whey protein and glucose or glucose alone. It is hypothesized that an enteral nutrition support regimen based on pressurized whey protein and glucose promotes positive protein balance through increased protein synthesis or reduced protein breakdown compared to glucose alone.

Patients who are randomly allocated to this group will receive a drink made of anhydrous beet dextrose and pressurized whey protein in water (200 g/L + 100g/L). Patients will sip the drink for 4 hours of the 6 hour study.

The patients who are randomly allocated to this arm will receive a drink composed of anhydrous beet dextrose in water (200g/L). They will sip the drink for 4 hours of the 6 hour study.

The patients will sip the oral nutrition support (in the form of a drink) over the course of 4 hours within each 6 hour study. Each patient will be studied once before surgery and once after surgery.

Protein balance is assessed using the stable isotope tracer C-13 leucine. Protein breakdown, protein synthesis and amino acid oxidation are measured through blood and expired air samples.

Inclusion Criteria: age older than 18 years ASA class I to III colorectal surgery for non-metastatic disease (including right, transverse, left, sigmoid, subtotal, total and hemicolectomy and low anterior resection) body mass index >17 and <30 kg.m-2 stable weight over the preceding three months (<10 % body weight loss) serum albumin >35 g/L Exclusion Criteria: severe cardiac, renal or hepatic failure diabetes hyper and hypothyroidism active inflammatory bowel or diverticular disease musculoskeletal or neuromuscular disease anemia (hematocrit <30) albumin < 25 g/l pregnancy use of steroids.