Nutritional Support in ICU - Surgery - Lecture Slides, Slides of General Surgery

Download Nutritional Support in ICU - Surgery - Lecture Slides and more Slides General Surgery in PDF only on Docsity! Nutritional Support in the ICU Docsity.com Reasons for Support Limit catabolism Substrate for healing Increase survival Docsity.com Stimuli for Stress Response Blood volume pH/pCO2/pO2 Emotion/pain/fear Substrate availability Temperature Infection Tissue injury Docsity.com Goals of Stress Response Maintain energy substrates (GLUCOSE) Maintain oxygen delivery Minimize further injury Docsity.com Response to Stress/Injury Neurohormonal - “Counterregulatory Hormones” • Glucagon • Epinephrine • Glucocorticoids Inflammatory Mediators • IL-1, IL-2, IL-6 • TNF-a • IFN-g Docsity.com Energy Substrates: Carbohydrates Glucose - parallels degree of injury Increased hepatic production of 3 - carbon precursors (fat/AAs) Breakdown of liver glycogen Docsity.com Energy Substrates: Amino Acids Skeletal muscle breakdown skewed toward alanine and glutamine Muscle nitrogen transferred to visceral organs • Glutamine major source for enterocyte oxidation • Glutamine transfers ammonia groups in kidney • Alanine in liver leads to gluconeogenesis Docsity.com Energy Substrates: Fat Lipolysis under catecholamine regulation Provides 3-carbon fragments to the liver Major provider of energy substrates in early sepsis and trauma (regulated through leptin?) Docsity.com Harris-Benedict Equation Estimates Basal Metabolic Rate (BMR): • Male BMR kcal/day = 66.47 + 13.7 (kg) + 5 (cm) - 6.76 (yrs) • Female BMR kcal/day = 665.1 + 9.56 (kg) + 1.85 (cm) - 4.68 (yrs) Harris-Benedict Equation Docsity.com Harris-Benedict Equation Factors to add to the BMR: • 25% - mild peritonitis, long bone fracture or mild/moderate trauma • 50% - severe infection, MSOD, severe trauma • 100% - burn of 40 to 100% TBSA Docsity.com Nitrogen Balance Measure/estimate all sources of nitrogen output • stool, urine, skin, fistulae, wounds, etc. Measure all sources of nitrogen input • enteral or parenteral nutrition Docsity.com Metabolic Cart Indirect Calorimetry: Theory Measures O2 absorbed in lungs Assumptions of Fick equation, at steady state O2 absorbed equals O2 consumed Metabolic rate in cc of O2 per minute Conversion 5kcal/liter O2 24 hour steady state measurement recommended Theory - start with a formula, tune it up long-term with the metabolic cart! Docsity.com Metabolic Cart - Indirect Calorimetry: Results RQ or respiratory quotient (CO2 expired/O2 inspired) 0.6 - 0.7 starvation/underfeeding 0.84 - 0.86 desired range/mixed fuel utilization 0.9 - 1.0 carbohydrate metabolism 1.0 + overfeeding/lipogenesis Docsity.com Other Clinical Parameters Wound healing Measured proteins • Albumin (t½ = weeks) • Prealbumin (t½ = days) Non-water weight gain Docsity.com Nutrients Fat - essential linolenic, linoleic, arachidonic acids • 9 kcal/gm Protein - essential and branched chain AA in TPN • 4 kcal/gm - not to be included in calorie estimates • no glutamine in TPN due to instability Carbohydrates - converted to glucose • 3.4 kcal/gm (4.0 kcal from endogenous source) Docsity.com Nutrients Trace Minerals • Chromium, copper, zinc, manganese, selenium, iron Vitamins • Thiamine • Folate • Vitamin C Docsity.com Rules of Thumb: TPN Want 25 - 35% solution of dextrose Want 4.25 - 6% AA solution • normal 0.8 gm/kg/day up to 2.0 gm/kg/day Kcal/nitrogen ratio • normal 300:1 • post-op 150:1 • trauma/sepsis 100:1 Lipids 10 - 20% at least twice per week Docsity.com Potential Reasons for TPN Failure TPN increases blood glucose if not strictly controlled • numerous studies now show hyperglycemia increases mortality and infectious complications Does not contain glutamine Docsity.com Why Enteral? Preservation of villous architecture • may prevent translocation • role of translocation unclear in humans • good study in BMT patients Ability to give glutamine • major fuel of enterocytes • major nitrogen transfer agent to viscera • in catabolic stress may be an essential AA Docsity.com Timing of Enteral Feeds Many studies claim benefits to early EN Meta-analysis (Marik and Zaloga Crit Care Med. 2001) • looked at 27 randomized,prospective studies • early EN had lower infections (RR 0.45) • early EN had shorter LOS (2.2 days) Docsity.com Anabolic Steroids (Oxandrolone) Hart et al. Annals of Surgery. 2001 • increases muscle protein net balance Wolf et al. Annals of Surgery. 2003 • improves net protein balance Demling. J Trauma. 1997 • increases weight gain in recovery phase post burns NO data that LOS different Physical therapy assessments were better Docsity.com Refeeding Syndrome In severely malnourished Development of severe electrolyte abnormalities: • phosphorous, potassium, magnesium As muscle mass, cell mass, and ATP repleted: • may reach critically low values, cardiac arrest Docsity.com Theoretical Advantages of Early Enteral Nutrition 1. Ameliorate the stress response, hypermetabolism, and hypercatabolism. 2. Provide gut stimulation to prevent atrophy and the loss of immunologic and barrier functions of the gut. 3. Minimize rapid onset of acute malnutrition. 4. Decrease LOS and complication rates. Docsity.com Lipid Goals High calorie, low volume Suggested max calories - no more than 50% of non-protein Kcal, or < 1 cal/Kg/hr Minimum to prevent EFAD is 2 x 500 cc bottles/week Diprivan (propofol) = 1calorie/ml Docsity.com Consequences of Overfeeding 1. Azotemia - patients > 65 years and patients given > 2g/kg protein are at risk. 2. Fat-overload syndrome - recommended maximum is 1g lipid/kg/d. Infuse IV lipid slowly over 16 - 24 hours. 3. Hepatic steatosis - patients receiving high carbohydrate, very low fat TPN are at risk. 4. Hypercapnia - makes weaning difficult. 5. Hyperglycemia - increases risk of infection. Glucose should not exceed 5 mg/kg/min (4 mg/kg/min for diabetics). Docsity.com Consequences of Overfeeding 6. Hypertonic dehydration - can be caused by high-protein formula with inadequate fluid provision. 7. Hypertriglyceridemia - propofol, high TPN lipid loads, and sepsis increase the risk. If the patient is hypertriglyceridemic, decrease lipid to an amount to prevent EFAD (500 cc 10% lipid twice weekly) and monitor. Docsity.com