Surgical Nutrition

1. Surgical Nutrition

2. Impact on Outcome • For well nourished or mildly malnourished general surgery patients, peri-operative nutritional support did not improve outcome and actually was associated with increased septic complications after surgery both pulmonary and intra-abdominal. • For severely malnourished patients before a major surgical procedure, peri-operative nutritional support reduced postoperative complications (wound complications, wound failure, prolonged hospital stay, ICU days, use of hospital resources) by about 10%, without significant increase in infectious complications.

3. Who will need it? • Well nourished and mildly malnourished patients who cannot take oral food for more than one week post operatively to avoid prolonged starvation. • Severely malnourished patients undergoing general surgery procedures. • All critically ill patients (Sepsis patients, Multiple Injury patients Burn patients, etc). • Patients whom you predict cannot use their gut for prolonged period of time (Short gut syndrome, EC fistula, etc).

4. When to Start? • Preoperatively in severely malnourished patient undergoing a major surgical operation. • Immediately postoperatively in severely malnourished patients. • Immediately after major trauma, sepsis, major burns. • Normal or mildly malnourished patient who is unable to eat on his own by 7 days after surgery.

5. Metabolism • Nutritional implications in surgical diseases are numerous and include anorexia, sodium and fluid retention, accelerated gluconeogenesis, hyperglycemia, insulin resistance, and lipid intolerance. • In reviewing body nutrient metabolism, one must consider body energy stores.

6. Metabolism • Triglyceride storage in the typical male consists of 140,000 calories. • Muscle contains 24,000 calories as protein, 2000 calories as glycogen, 3000 calories as triglyceride. • Liver contains 300 cal as glucose in glycogen form, 500 cal as triglyceride. • Unstressed starvation uses adipose stores.

7. Metabolism (unstressed) • During the first 48-72 hrs increased use of fat stores, and most tissues except RBCs, WBCs, and renal medulla oxidize lipid stores. • Brain has an obligate glucose requirement, over 3-5 days uses fatty acids for energy.

8. Assessment of Nutritional Status • Weight loss is a significant indicator • More than 10% unintentional loss in 6 month period. • 5% loss in 1 month. • Anorexia, persistent nausea, vomiting, diarrhea, malaise. • Loss of subcutaneous fat, muscle wasting, edema, ascites.

9. Evaluation of Nutritional Status(Difficult) • Weight loss • Serum markers • Albumin level T1/2 = 21 d • Transferrin T1/2 = 8 d • Prealbumin level T1/2 = 2-3 d • Immune competence (delayed hypersensitivity reaction, total lymphocyte count)

10. Assessment • Signs of specific nutritional deficiencies. • Skin rash • Pallor • Cheilosis • Glossitis • Gingival lesions, hepatomegaly, neuropathy, dementia.

11. Evaluation of Body Composition • Ideal body weight (IBW) • Men 106lb+ 6lb for each inch over 5 feet • Women 100lb + 5lb for each inch over 5 ft. • IBW depends on patient age, body habitus. • Other measurements include triceps skin fold, arm circumference.

12. Body Composition • BMI characterizes degree of obesity. • = weight(kg)/total body surface area. • BMI over 40 or over 35 with co-morbid conditions are considered candidates for surgical treatment. • Severe obesity is associated with significant increase in morbidity and mortality.

13. Laboratory Markers • Serum proteins • Albumin half life 20 days • Transferrin half life 8.5 days • Prealbumin half life 1.3 days • Retinol binding protein 0.4 days • Severe hypoalbuminemia <2 poor outcomes • Albumin not a good short term marker

14. Energy Expenditure • Can be measured by the respiratory quotient. • RQ= CO2 production(VCO2)/O2 consumption (VO2). • Indirect calorimetry allows for gas analysis and calculation of RQ.

15. RQ • RQ of 1.0 predominant glucose utilization. • RQ of 0.7 and 0.8 consistent with fat and protein utilization. • RQ higher than 1.0 suggests over feeding and lipogenesis.

16. Nutritional Requirements • Total energy requirements. • Total protein requirements. • The relative distribution of calories between carbohydrates, fats, and protein.

17. Energy Requirements • Harris-Benedict equation estimates BEE at rest. • Men 66 + (13.7x weight) + (5x height) –(6.8 x age). • Women 65 + (9.6 x weight) + (1.7 x height) – (4.7 x age) • Most require 25-35 kcal/kg/day. • Stress increases these values.

18. Stress • Low stress 1.2 x BEE • Moderate stress 1.2-1.3 x BEE • Severe stress 1.3-1.5 x BEE • Major burn injury 1.5-2.0 x BEE • Requirements are increased by fever, infection, activity, burns, head injury, trauma, renal failure, surgery. • Decreased by sedation, paralysis, B blocker

19. Stress Factors

20. Carbohydrate (30-60% of Total) • Serve as main energy source for cellular metabolism when energy is rapidly required following stress. Each gram releases 4 kcal. • Also important in membranes as glycoproteins, glycolipids, carbon backbone of essential amino acids.

21. Carbohydrate (30-60% of Total) • Glucose, galactose, fructose main six carbon sugars. • CHO are stored as glycogen in liver (40%), muscle (60%), cardiac muscle. • Stores depleted in 48hrs (starve), 24 hrs (stress).

22. Carbohydrate • Liver glycogen is only source of free glucose available systemically from carbohydrate stores. • Muscle glycogen is used for muscle itself, and not available for other tissues. Does not have G-6-P to do this.

23. Protein • As opposed to CHO, protein absorption in intestine is incomplete, leading to a mixture of free AA and oligopeptides. • A major portion of protein digestion products are absorbed by luminal cells as small peptides, subsequently digested to yield free amino acids inside the cell.

24. Protein • Essential components of all living cells, involved in virtually all bodily functions. • Serve as enzymes, hormones, neurotransmitters, immunoglobulins, transport proteins. • Total protein in a healthy male is 15-18% of body weight. • Protein is not stored, should all be considered functional.

25. Protein • Obligatory turnover rate of proteins. • 2.5% of total body protein is broken down and re-synthesized every 24hrs. • Half of this is daily digestive process, maintenance of immune function, muscle protein synthesis, hemoglobin turnover • Protein yields 3.5 kcal per gram.

26. Protein Requirements • Most healthy individuals require 0.8-1.0 g protein/kg/day. • Mild stress 1-1.2 g/kg/day. • Moderate stress 1.3-1.5 g/kg/day. • Severe stress 1.5-2.5 g/kg/day. • Renal failure (more) • Hepatic encephalopathy (less)

27. Nitrogen Balance • A crude measurement of protein consumption. • Difference between net nitrogen intake and excretion. • Positive balance indicates more protein ingested than excreted. • Negative balance is catabolism. • Protein excretion in urine= nitrogen x 6.25g.

28. Amino Acids • Most AA metabolized by liver • Branched chain AA are metabolized by muscle. • Patients require at least 20% of their protein intake as essential AA. • Glutamine is most abundant AA in blood, a principle food for enterocytes, mucosal integrity, macrophage and lymphocyte proliferation.

29. Lipids • Where CHO and protein are fairly soluble, lipids are characterized by poor solubility in aqueous solutions, good in organic solvents. So digestion presents some unique problems. • Role of lipids include energy source, cell membrane structure, lubricant for body surfaces, joints, and mucous membranes.

30. Lipids • Should provide 25-40% of total calories. • Fatty acids a major source of fuel for heart, liver, skeletal muscle. • Liver oxidation of fatty acids yields ketones which are used by the heart, brain, muscle during starvation. • During the fed state, insulin stimulateslipogenesis and fat storage, inhibits lipolysis in adipocytes.

31. Triglycerides • Long Chain must be emulsified by bile salts to for micelles. • Must be hydrolyzed by pancreatic lipase in the proximal small bowel for absorption to occur. • Medium Chain absorbed directly by enterocytes, thru portal system to liver. • Readily absorbed despite severe deficiencies in pancreatic function. Less steatorrhea.

32. Essential Fatty Acids • During parenteral nutrition, at least 3-5% of total calories as fat is necessary to prevent essential fatty acid deficiency. • Linoleic and Linolenic acid are precursors to prostaglandins and eicosanoids. • Deficiencies result in dermatitis,ecchymosis, alopecia, anemia, edema, thrombo, respiratory distress. • Manifestations occur in 4-6 weeks.

33. Vitamins • Deficiencies can occur in severely malnourished patients, chronic nutritional support. • Impaired wound healing can be a direct result of deficiencies in Vitamin A, C, and zinc.

34. Deficiencies • Vitamin A- Wound healing • Vitamin D- Rickets, osteomalacia • Vitamin E- Anemia, ataxia, nystagmus, edema, myopathy. • Vitamin C- Wound healing • Thiamine- Encephalopathy • B6- neuropathy…

35. Stress • The same events as starvation. • Much more accentuated tissue protein breakdown in order to: • Supply increased demands of energy • Supply building blocks for acute phase reactant proteins by the liver. • This accentuated protein breakdown is stimulated by • Increased steroid production • Cytokines associated with acute stress response • Nitrogen loss: • 5-8 gm/d normally • 2-4 gm/d after several days of unstressed starvation • 30-50 gm/d under severe stress (multiple trauma, sepsis, burns)

36. Critical Illness • Metabolic rate is increased • While patients are in negative nitrogen balance, protein synthesis is active centrally • Fat not as available as energetic substrate • Cortisol and catecholamines block lipolysis and oxidation of fatty acids to ketone bodies

37. Metabolism (stressed) • Hypermetabolism associated with major catabolic illness, trauma, major surgery is a significant change. • Increase in ACTH, epinephrine, glucagon, cortisol production. • As in unstressed, glycogen is used up in 12-24hrs. • But gluconeogenesis continues at accelerated rate.

38. Metabolism (stressed) • Muscle protein, in addition to providing a source for gluconeogenesis, serves as a substrate for acute phase protein synthesis by providing necessary AA. • Liver reprioritizes to produce acute phase proteins rather than visceral proteins. • Increased glutamine and alanine released from muscle for gut and liver respectively. • Hyperglycemia common because of gluconeogenesis and insulin resistance.

39. Alterations During Stress • CHO: ACTH, cortisol, catecholamines, glucagon. • Hyperglycemia frequently present during stress secondary to relatively low insulin level and peripheral insulin resistance. • Insulin inhibited by catecholamines, sympathetic nervous system, somatostatin. • Catecholamines and cortisol contribute to insulin resistance peripherally.

40. Alterations During Stress • Liver glycogenolysis, gluconeogenesis stimulated by catecholamines, cortisol, glucagon. • The glucose produced is essential for RBCs, WBCs, renal medulla, neural tissue, wound tissue. • Protein synthesis increases during stress • Net proteolysis and negative nitrogen balance are characteristic of severe stress.

41. Alterations During Stress • Alanine release from peripheral tissue increases as it is the major source of AA substrate for gluconeogenesis in the liver. • During severe sepsis, muscle protein loss may occur at 240 g protein per day. • IL-1 may play a role in stimulating proteolysis in this setting. • Lipids: During severe stress, lipolysis is stimulated by increased cortisol, catecholamines, glucagon, GH, ACTH, sympathetic activity.

42. Hormonal Response to Injury • Insulin • Glucagon • Catecholamines • Cortisol • ADH • Renin

43. Protein Synthesis in Critical IllnessReprioritization Albumin Retinol binding protein Transferrin Acute phase proteins Immune proteins

44. Nutritional Supplementation • Benefits high risk patients such as severely malnourished, critically ill, burns, severe trauma. • Delayed oral intake 7-10 days. • Enteral route is indicated in all patients with an intact, functioning GI tract. • Prevents intestinal atrophy, gut immune function, inhibition of stress induced increase in intestinal permeability.

45. Nutritional Supplementation • Oro-enteric, naso-enteric, gastrostomy, jejunostomy. • Small bore NG tubes can be use for short period of time. • Gastrostomy and jejunostomy for long term. • Complications in placement, organ injury, aspiration, malfunction, leaks, sinusitis, erosion..

46. Supplementation • Relative contraindications to enteral feeding: • Mesenteric ischemia • Bowel obstruction • Sepsis • Pancreatitis • Fistula • SBS

47. Role of Gut in Critical Illness • Mice fed TPN: • Reduced GALT T- and B-Cells • Reduced IgA production in GI AND Respiratory Tracts • Reduced immunity to respiratory tract infectious challenges - viral and bacterial • Enteral feeding: • Restored GALT cell lines • Restores immune function • Restores ability to resist URI challenges Ann Surg, 1997

48. Enteral Feeding • The most frequently cited advantage of enteral feeds is relative decreased infection rate in critically ill patients. • Glutamine- mucosal integrity, immune function. Levels fall significantly during severe stress and sepsis. • Arginine- improves N balance, T-cell responsiveness, reduces infection complications. • Omega-3 fatty acids- precursors for eicosanoids, immunoregulatory role possible.

49. Over Feeding • Detected if respiratory quotient (RQ) is above 1 (determined by the metabolic cart). That means that there is lipogenesis. • Has adverse effects • Respiratory failure due to excess CO2 production during lipogenesis. • Hepatic failure due to excess fatty liver infiltration and cholestasis. • Overfeeding has to be completely avoided as it is harmful to the patient.

50. Parenteral Feeds • TPN- indicated when GI tract is unavailable or nonfunctional. • Via Central catheter due to hyperosmolarity of the solutions. • Complications related to catheters frequent. • Severe metabolic complications can occur. • Hyperglycemia, hypoNa, hypoK, hypoMg, hypoP, hypereverything.