Presented by : Dr. Mohammad Tarawneh

The human body is an engine designed to burn fuel in order to perform work. The fuels we utilize are called nutrients. come in three types : carbohydrates, lipids, and protein. Dietary nutrition supplies the nutrients that drive cellular metabolism. The chemical processes that maintain cellular viability consist of catabolic (breakdown) and anabolic (synthesis) reactions. Catabolism produces energy, whereas anabolism requires energy

Carbohydrates. - Glucose is the functional unit of carbohydrate metabolism. - It is the body's primary energy source, providing 30% to 40% of calories in a typical diet. - The brain and red blood cells rely almost exclusively on a steady supply of glucose to function. - each gram of enteral carbohydrate provides 4 kcal of energy. - absorption is generally completed within the first 1 to 1.5 m of small intestine.

Lipids - Fatty acids are the functional units of lipid metabolism. - They comprise 25% to 45% of calories in the typical diet. - During starvation, lipids provide the majority of energy in the form of ketone bodies converted by the liver from long-chain fatty acids. - Each gram of lipid provides 9 kcal of energy. - Roles of lipids. Whereas carbohydrates are used exclusively for fuel, lipids have additional functional and structural roles. - In addition to energy storage, lipids comprise membranes in cells, serve as signaling factors, and are contained in certain vitamins. - Digestion and absorption of lipids is complex and utilizes nearly the entire GI tract.

Protein - Amino acids are the functional units of protein metabolism. - Whereas the body has energy reserves for carbohydrates and lipids, there are no stores of protein. - All of the body's protein serves a functional purpose. - Proteins are important for the biosynthesis of enzymes, structural molecules, and immunoglobulins.

When energy needs are unmet by nutrition, muscle breakdown yields amino acids for hepatic gluconeogenesis, which can lead to wasting and deconditioning in severe circumstances. Each gram of protein can be converted into 4 kcal of energy. Daily protein requirements in the average healthy adult without excessive losses are approximately 0.8 g/kg body weight. Once digested, almost 50% of protein absorption occurs in the duodenum, and complete protein absorption is achieved by the mid-jejunum.

Vitamins and trace elements In addition to the principle sources of energy, our metabolic machinery also requires various other substances in order to function efficiently. Vitamins are involved with wound healing and healthy immune function while many trace elements are important as cofactors and enzymatic catalysts. These substances cannot be synthesized de novo and therefore must be part of dietary intake. Deficiencies can have a multitude of detrimental effects.

Nutritional Assessment - Nutrition plays a vital and often underappreciated role in the recovery of patients from surgery. - It is estimated that between 30% and 50% of hospitalized patients are malnourished. - Poor nutrition has deleterious effects on wound healing and immune function, which increases postoperative morbidity and mortality. - Identification of those at risk for malnutrition is made through ongoing clinical assessments by vigilant clinicians.

CLINICAL ASSESSMENT - History - Physical examination - Anthropometric measurements such as triceps skinfold thickness and midarm muscle circumference reflect body- fat stores and skeletal muscle mass, respectively. - Laboratory tests: Albumin, prealbumin, and transferrin

Nutritional Support The need for nutritional support should be assessed continually in patients both preoperatively and postoperatively. Patients with a significant degree of preoperative malnutrition have less reserve, tolerate catabolic stress and starvation poorly, and are at higher risk for postoperative complications.

Routes of Nutritional Support - Enteral - Parenteral nutrition: is indicated for patients who require nutritional support but cannot meet their needs through oral intake and for whom enteral feeding is contraindicated or not tolerated. * Peripheral parenteral nutrition (PPN) is administered through a peripheral IV catheter. * Total parenteral nutrition (TPN) provides complete nutritional support