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Nutrition. Dr James F Peerless July 2013. Objectives. Introduction to nutrition Assessment of the patient Feeding requirements Macro- & micronutrients Enteral vs. parenteral feeding Refeeding syndrome. Introduction. Nutrition support: enteral or parenteral provision of
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Nutrition Dr James F Peerless July 2013
Objectives • Introduction to nutrition • Assessment of the patient • Feeding requirements • Macro- & micronutrients • Enteral vs. parenteral feeding • Refeeding syndrome
Introduction • Nutrition support: • enteralor parenteral provision of • calories • protein • electrolytes • vitamins, minerals • trace elements • fluids • Goal of therapy is to supply each substrate in the right quantity necessary to meet the metabolic needs of each patient Total energy Protein Lipids (fat) Carbohydrates Micronutrients
Nutrition • Aims of nutritional support on the ICU: • Provide exogenous substrates to meet macro and micronutrient requirements in dependent patients • Help protect vital visceral organs and attenuate breakdown of skeletal muscle • Reduce net protein catabolism • Contraindications to commencing feed (enteral or parenteral) on ICU: • Able to resume full oral diet within 3 days • Inappropriate for ethical reasons
Assessment of nutritional status • It is estimated that 60% of patients are malnourished prior to hospital admission • Malnutrition is associated with a poor outcome – increased LoS and incidence of complications in critical care. • Assessment difficult • Anthropometric measurements good for populations • BMI does not reflect acute changes • Biochemical tests have limitations
Subjective Global Assessment History • Weight change (chronic and acute) • Changes in food intake • GI symptoms (N, V, D, anorexia) • Functional impairment Examination • Loss of SC fat (chest, triceps) • Muscle wasting (temporal, deltoid, gluteal) • Oedema • Ascites
Nutritional Requirements • Harris Benedict Equation • For the calculation of BMR (kcal/day) • BMR for a healthy, afebrile individual • ≈25 kcal/kg/day • Also the Schofield Equation • Male BMR = (13.75 ×wgt) + (5 × hgt) – (6.78 × age) + 66 • Female BMR = (9.56 × wgt) + (1.85 × hgt) – (4.68 × age) + 655
Nutritional Requirements • Harris Benedict Equation • For the calculation of BMR (kcal/day) • BMR for a healthy, afebrile individual • ≈25 kcal/kg/day • Fever: 10% for each 1°C above 37°C • Sepsis: 9% (irrespective of T°C) • Surgery: 6% if post trauma or surgery
Critical Illness and Requirements • Acute critical illness • Catabolism > anabolism • CHO are preferred energy source (fat mobilisation is impaired) • Aim of nutritional support to minimise muscle protein breakdown • Acute initial phase of critical illness 20-25kcal/kg/day • Recovery phase • Anabolism > catabolism • Nutritional support provides substrates for: • correction of hypoproteinaemia • Reparation of muscle loss • Replenishes nutritional stores • Recovery/anabolic phase 25-30kcal/kg/day
Nutritional Requirements Macronutrients • Provide energy • Protein: 5.3 kcal/g • Lipid: 9.3 kcal/g • Carbohydrate: 3.75 kcal/g Micronutrients • Required in small amounts to maintain health but do not provide any energy
Protein Requirements • 1.5 g kg-1 day-1 • 6.25 g contains 1 g of nitrogen ~ 0.20g nitrogen/kg/day. • Nitrogen losses are large in critically ill patients Nitrogen output = urinary urea/mmol/24 hours x 0.033 + obligatory losses + extra renal losses • Obligatory losses • estimated as 2-4g nitrogen/day (skin, hair, faeces etc) • Extra renal losses include: • Pyrexia • Inflammatory bowel disease • GI fistulae • Extensive bed sores • Burn exudates
Protein Requirements in Specific Conditions • Renal failure • Haemofiltration associated with increased protein losses (~10%) • Liver failure • Protein requirements dependent on underlying function of the liver: • Compensated cirrhosis 0.19-0.20gN/kg/day • Decompensated cirrhosis 0.25-0.30gN/kg/day • Post-transplant 0.25-0.30gN/kg/day • Acute (fulminant) liver failure 0.20-0.25gN/kg/day
Lipid Requirements • Lipid • Limit to 40% of calorie intake • Critically ill patients require approximately 0.8-1.0g/kg/day of lipid. • NB: propofol is a lipid source • Each ml contains of 1% propofol contains 0.9kcal and can increase the risk of both fat and total calorie overfeeding and micronutrient deficiency
Carbohydrate Requirements • Carbohydrate • Excess intake above this can result in: • hyperglycaemia • lipid synthesis • increased carbon dioxide production Carbohydrate + O2 = water + CO2 + energy production
Micronutrient Requirements • Vitamins • Organic molecules essential for life; not synthesised by higher organisms • Fat-soluble: A, D, E, K • Water-soluble: C, B complex • Minerals • Single elements essential to life: Ca, P, Mg, Zn, Fe, I • Trace elements • Essential to life, but in minute quantities: Cu, Co, Mn, Ni, Mo, Cr
Micronutrient Requirements • No set levels for micronutrient requirements for the critically ill • aim for the normal recommended daily allowance • Specific disease states • Thiaminedeficiency in alcoholics • Vitamin B12deficiency in patients post gastrectomy or total ilealresection • Zinc losses from pancreatic fistulae • Phosphate, magnesium and potassium deficiencies upon refeeding a malnourished patient • Micronutrient supplementation in patients with renal failure needs to be undertaken cautiously due to risks of toxicity.
Feeds • Standard formulation suitable for most patients • Isotonic • Lactose-free • Protein • Mixture of simple/complex CHO • Long-chain fatty acids • Micronutrients • Pro-biotics • Variety of formulations available: • Concentrated for fluid restriction • Pre-digested for enzyme deficiencies
Enteral Nutrition • Continuous vs bolus • No difference in mortality, infection, ITU LoS • Monitoring • Measurement of gastric residuals to minimise risk of accumulation and aspiration • This is shown to correlate poorly with aspiration, and disrupts absorption. • Consensus towards only measuring residual if clinically indicated.
Complications • Aspiration • Backrest elevation • Post-pyloric feeding • Surgical/percutaneous feeding • Motility agents • Diarrhoea • Dehydration • Metabolic abnormalities • hyperglycemia • micronutrient deficiencies • refeedingsyndrome • Mechanical complications
Parenteral Nutrition • Contains a carefully formulated mixture of macronutrients, and fluid • Can be used to provide 100% of patient’s requirements • Varying formulations (protein/lipid ratios depending on patient requirement) • Minerals and trace elements are added to the bag by the pharmacy.
Initiation of PN • Deliver via central venous route • High osmotic load poorly tolerated by peripheral veins • <30d CVC, PICC • >30d tunneled lines: Groshong, Hickman • Dedicated port • Risk of infection
Monitoring • Strict input/output measurement • Daily electrolytes, until regime fully established • LFTs, and triglycerides once a week
When to Start? • Early provision (<48h) of PN to well-nourished patients does not alter mortality • Early PN in well nourished patients may be associated with increased risk of infection (by 5%), even if EN is contraindicated. • Higher incidence of hypoglycaemia in late PN Koretz RL, Lipman TO, Klein S, American Gastroenterological Association. AGA technical review on parenteral nutrition. Gastroenterology 2001; 121:970. Kerrie et al. Early versus late parenteral nutrition in the adult ICU: feeding the patient or our conscience? J Can Anesth (2012) 59:494–498
Glutamine • Precursor for nucleotide synthesis • Important fuel source for new cells (e.g. GI mucosa) • Therefore helps maintain gut mucosal function, integrity and immune function • Also has anti-oxidant actions which were thought to be useful in critical illness: however, REDOX trial suggests an increase in 28-day mortality. Heyland et al. A Randomized Trial of Glutamine and Antioxidants in Critically Ill Patients. NEJM 368;16 1489-1497
Complications • Bloodstream infection • Metabolic abnormalities • hyperglycemia • serum electrolyte alterations • macro- or micro-nutrient excess or deficiency, refeeding syndrome • Wernicke's encephalopathy • hepatic dysfunction • Problems related to venous access
Refeeding Syndrome • Results from rapid changes in fluids and electrolytes • Pathophysiology based on total/partial starvation followed by refeeding • Occurs in up to 35% of ITU patients • Life-threatening, especially if associated with thiamine deficiency Mehanna HM, Moledina J, Travis J. Refeeding syndrome: what it is, and how to prevent and treat it. Br Med J 2008; 336:1495 – 1498.
Refeeding Syndrome • Defined primarily by manifestations of severe hypophosphataemia • Cardiovascular collapse • Respiratory failure • Rhabdomyolysis • Seizures • Delirium • Hypokalaemia • Hypomagnesaemia
Identifying at-risk patients • One or more criteria • BMI below 16 • Unintentional weight loss >15% in 3–6 months • Little or no nutrient intake for more than 10 days • Low potassium, phosphate, magnesium before feeding. • Two or more criteria • BMI below 18.5 • Unintentional weight loss >10% in 3–6 months; • Little or no nutrient intake for more than 5 days; • History of chronic drug (insulin, diuretics, antacids) use or alcohol misuse. NICE CG32: Nutrition Support in Adults; February 2006
Summary • During critical illness: • Marked catabolic process • Increase in BMR • Relative insulin resistance • Malnutrition associated with impaired immune function and increased morbidity • Early recognition and correction of nutritional status is crucial
ESPEN Guidelines • Patients should be fed because starvation or underfeeding in ICU patients is associated with increased morbidity and mortality • All patients who are not expected to be on normal nutrition within 3 days should receive PN within 24 - 48 hours if EN is contraindicated or not tolerated. Singer et al. ESPEN Guidelines on Parenteral Nutrition: Intensive care. Clinical Nutrition 28 (2009) 387–400
Summary of Daily Requirements • Calories 25 kcal/kg • Protein 0.25 g N2/kg • Glucose 2 g/kg • Fat 2 g/kg • Water 30 mL/kg • Sodium 1.2 mmol/kg • Potassium 0.8 mmol/kg
Reference • Smith T, Pinnock C, Lin T. Fundamentals of Anaesthesia, 3rd Edition; 2009. Cambridge: Cambridge University Press. • Wellesley H. Nutrition in ICU, 2007. http://www.frca.co.uk/article.aspx?articleid=100979#accessed 26.06.13 • Macdonald K, Page K, Brown L, Bryden D. Parenteral nutrition in critical care. Continuing Education in Anaesthesia, Critical Care & Pain, 2012; 13(1): 1-5 • Campbell Edmondson W. Nutritional support in critical care: an update. Continuing Education in Anaesthesia, Critical Care & Pain, 2007; 7(6): 199-202 • Uptodate.com (accessed 28.06.13) • Nutritional support in critically ill patients: parenteral nutrition • Nutritional support in critically ill patients: enteral nutrition • Nutritional support in critically ill patients: an overview