Surgical Nutrition Vic V.Vernenkar, D.O. St. Barnabas Hospital Dept. of Surgery

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.

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).

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.

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.

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.

Metabolism (unstressed)  During the first 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.

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.

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)

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

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.

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.

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

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.

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.

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

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 kcal/kg/day.  Stress increases these values.

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

Stress Factors

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.

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).

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.

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.

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.

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.

Protein Requirements  Most healthy individuals require g protein/kg/day.  Mild stress g/kg/day.  Moderate stress g/kg/day.  Severe stress g/kg/day.  Renal failure (more)  Hepatic encephalopathy (less)

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.

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.

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.

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 stimulates lipogenesis and fat storage, inhibits lipolysis in adipocytes.

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.

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.

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.

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

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)

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

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 hrs.  But gluconeogenesis continues at accelerated rate.

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.

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.

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.

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.

Hormonal Response to Injury  Insulin  Glucagon  Catecholamines  Cortisol  ADH  Renin

Protein Synthesis in Critical Illness Reprioritization Albumin Retinol binding protein Transferrin Acute phase proteins Immune proteins

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.

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..

Supplementation  Relative contraindications to enteral feeding:  Mesenteric ischemia  Bowel obstruction  Sepsis  Pancreatitis  Fistula  SBS

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

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.

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.

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.

Parenteral Feeds  Refeeding Syndrome- may develop rapidly in severely malnourished patients started on TPN.  Most frequently associated with admin of high calorie supplements, supplements with high carbohydrates.

TPN Orders  Calculate VOLUME requirements/24h.  Determine PROTIEN requirements g/kg/d.  Calculate daily CALORIES kcal/kg/d.  Determine % to be given as protein, CHO, fats.  Add ELECTROLYTES, TRACE ELEMENTS.  Co-administer Lipids to prevent fatty acid deficiency.  Lipids give more calories in less volume…  A 10% lipid sol. 1.1kcal/ml, 20% is 2.0 kcal/ml.

Take Home Messages  Nutritional supplementation reduces the risk of complications if given to severely malnourished patients undergoing major surgical procedures and in patients with severe sepsis, trauma and burns (by 10%) but does not impact the mortality.  Nutritional supplementation is not indicated in healthy subjects postoperatively until one week postoperatively or in patients who are predicted not to be not able to eat to avoid prolonged starvation.

Take Home Messages  Enteral feeding must be the first choice always for nutritional supplementation.  Parenteral nutrition is an important tool in the armamentarium, however it has a lot of inherited problems. Only used when enteral feeding cannot be done.  Overfeeding is very harmful for patients and must be avoided and looked for.