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Home , Refeeding syndrome

Nutrition in the Critically Ill Patient

14 : 5 Dilip R Karnad, S Sanjith, Mumbai Critically ill patients have severely deranged physiology which results in a significant alteration in their of essential nutrients. These may result from the illness itself as seen in diabetes, or pancreatitis, or physiological stress due to severe illness as in sepsis, burns, , or due to derangement of organ function as in hepatic or renal failure. Moreover, a significant number of critically ill patients also have alteration in appetite and the function of the gastrointestinal tract. Consequently, studies have revealed that underfeeding occurs in up to 30% of hospitalized and as many as 50% of ICU patients. Inadequate nutrition may alter immune responses, integrity of the gut mucosal barrier, synthesis and wound healing, thereby contributing to significant morbidity and mortality. Therefore nutrition is as important a part of treatment of a critically ill patient as are drugs and organ support. Up until a few years ago, the concept of nutrition in the ICU patient was thought of as one of nutritional support, where the main objective was to provide adequate calories and protein to maintain normal body structure and weight during the catabolic phase of the illness. More recently, this concept has been replaced by one of nutritional therapy, where the aim is to modify the contents of the diet in an attempting to attenuate the metabolic response to stress, to prevent oxidative cellular injury, and to favorably modulate immune response. These may be expected to 1. Preserve muscle mass and decrease autocannabalism (use of amino acids for calories) 2. Decrease infection and improve wound healing 3. Maintain gut barrier functions and supporting immune, renal, hepatic, muscle function 4. Reduce ICU length of stay, reduce morbidity and mortality and decrease cost of healthcare. Most critically ill patients have increased energy and protein requirements as a result of the hypercatabolic or “lytic state” (glyoclytic, proteolytic, lipolytic) state. They may also have a tendency to develop hypo- or hyperglycemia, either of which can adversely affect outcomes. The common physiological derangements contributing to these include elevated levels of cortisol, , catecholamines and . Inflammatory cytokines TNFa and IL-6 and bacterial endotoxin alter glucose utilization and enhance protein catabolism. like acute hepatic failure and altered gastrointestinal function can further worsen metabolic disturbances in critical illness. It is therefore evident that in normal healthy individuals, the hormonal response of the body adapts to intermittent feeding and can appropriately respond to changes in the dietary content. However, in critically ill patients, this adaptability is lost and nutrition has to be provided on a continuous basis and its content modified to match the metabolic and hormonal state of the body. In 2009, comprehensive guidelines on nutrition in the critically ill adult patients have been suggested by the American Society of Enteral and (A.S.P.E.N), Society of Critical Care (S.C.C.M) and the Canadian group. The present review is based mainly on these recommendations. Assessment of Nutritional Status In critically ill patients, the commonly used anthropometric or biochemical parameters of nutritional assessment are not helpful as edema may mask and hypoproteinemia is commonly due

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Table 1: Indications for use of parenteral nutrition in critically should be provided at least 1.2 – 2 gram of /kg actual ill patients body weight/day; this figure can go higher in polytrauma, 1. Previously healthy patient, no protein-calorie on burns and obese patients. admission Formulae and Preparations 1. Early EN is not feasible Total PN initiated only after 7 days of hospitalization When using parenteral nutrition, it is best provided as an 2. Unable to reach 100% of Supplemental PN initiated only after all-in-one bag which contains water, glucose, lipids, amino feeding goal by Day 7 7 days acids, vitamins and trace elements. Besides reducing costs 2. Protein-calorie malnutrition on admission and nursing time, this reduces the need for manipulation of 1. EN is not feasible PN initiated as soon as possible the intravenous infusion system, minimizing infection and 3. major upper GI , EN is not feasible also metabolic complications resulting from use of non- 1. Malnourished patient • PN initiated for 5-7 days pre- physiological combinations. operatively Initiation of Feeding • Elective surgery postponed for 5-7 days Enteral feeding should be started within the first 24- 48 hours • PN continued in post-opera- of admission and increased to reach the calculated nutritional tive period until EN possible goal over next 48-72 hours. Early enteral feeding helps 2. Previously health pa- • PN should not be initiated im- preserve structural integrity if the intestinal mucosa, preserves tient, no malnutrition mediate post-op • PN initiated only after 5-7 gut associated lymphoid tissue, reduces translocation of days if EN not possible intestinal bacteria and may thereby reduce disease severity. • PN given for <5-7 days has no However early enteral nutrition may be withheld in patients outcome benefit but associated in who are on high dose of vasopressor till such time with increased risk • PN should be initiated only if that they are fully resuscitated. In patients who cannot be fed duration of PN anticipated ≥7 orally, nasogastric tube feeding into the stomach is initiated. days. Parenteral nutrition should be initiated only under very Note: PN = parenteral nutrition, EN = enteral nutrition specific situations. Typically, it should be reserved only for patients who cannot be fed enterally, and is deferred for at least to increased vascular permeability or decreased hepatic 5-7 days in those patients who are not malnourished to start. synthesis. Subjective global assessment which includes assessment of weight loss, nutrient intake in the weeks prior Route to admission, nature and severity of disease, co-morbid Enteral feeding is the preferred mode feeding unless there are conditions and function of the gastrointestinal tract are used specific contra-indications. Enteral feeding is associated with to classify patients in normal, moderately malnourished, or significantly lower morbidity and mortality in ICU patients severely malnourished category. by preserving integrity of the gut mucosa, which derives up Calculation of Nutritional Require- to 70% of its nutrition from the luminal contents. Enteral ments feeding also stimulates splanchnic blood flow and neuronal activity, promotes release of protective IgA and induces The basal amount of energy required for maintaining lean secretion of gut hormones that promote trophic activity in body mass is known as resting energy expenditure (R.E.E). the intestinal mucosa. Enteral tube feeds may be delivered Indirect calorimetry remains the most accurate method in the stomach in most patients. Feeding via a tube placed in to determine resting energy expenditure in critically ill the small bowel (post-pyloric site) is preferred in patients at subjects. However this is time-consuming and requires costly high risk for aspiration or those with intolerance to gastric equipment and technical skills that are not widely available.1 feeding. Ileus, absence of bowel sounds or passage of flatus Various predictive equations are present in literature of which is not a contraindication to enteral feeding; continuous post- the Harris-Benedict equation is commonly used.2 None of pyloric feeding may be better tolerated by these patients. the predictive equations however were accurately predictive Common contraindications for enteral nutrition are severe of the R.E.E when compared with indirect calorimetry3 and prolonged ileus, intestinal obstruction and severe hemorrhagic hence should be used with caution especially in obese patients. pancreatitis. A general rule of thumb is to provide 25 Kcal/kg of ideal body weight; the requirement is much higher in sepsis, burns Parenteral is expensive, associated with significant and polytrauma. Of these 60 to 70 % of calories should be complications, and should only be used when specific provided by carbohydrates, and the rest by lipids; protein indications are present (Table 1). Parenteral nutrition in the calories should not be included in the calculation. Patients ICU is almost always administered via a central venous ; one lumen of the multi-lumen catheter is reserved 712 Nutrition in the Critically Ill Patient only for parenteral nutrition to avoid contamination and issues calorie goals often owing to frequent interruption of feeds for of incompatibility of mixtures. Nutrition may be provided via procedures or investigations like CT scans, ultrasonography peripheral venous cannulae and peripheral inserted central and transesophageal echocardiography. Early feeding of the in non-ICU patients. critically ill in the ICU is associated with a 50% reduction in mortality, but there is also a 50% increase in infection risk. Complications Infectious complications of enteral feeding are greatly reduced Complications common to all modalities and routes of when a strict feeding protocol is followed. This includes 30- nutrition are fluid overload, hyperglycemia, underfeeding and 45% propped up position, continuous feeding, of the refeeding syndrome. Fluid overload is common in patients gastric residual volume, judicious use of prokinetic agents and with oliguric renal failure or . Hyperglycemia is post-pyloric feeding in selected cases. seen in about 27% of ICU patients and may be due to pre- existing diabetes or the systemic inflammatory response The main reservations about widespread use of parenteral syndrome resulting in release of catecholamines and nutrition are the cost and the high incidence of complications corticosteroids, increased gluconeogenesis, insulin resistance with catheter-related blood stream infection being the and impaired glucose utilization. Hyperglycemia has been most dreaded with an attributable mortality of 12 to 25%. associated with increased morbidity and mortality and many Complications of parenteral nutrition are central line placement- patients will require intensive insulin therapy to keep blood related (pneumothorax, accidental arterial puncture and local glucose below a level of 200 mg/dl. hematoma formation), related to prolonged presence of the venous access (infection, venous thrombosis, central line Underfeeding is commonly inadvertent, and results from blockage) and metabolic (electrolyte disturbances, acid-base underestimation of the daily calorie or protein requirements of disorders, liver dysfunction, hyperglycemia and trace element patients and failure to take into account increased requirements or essential fatty acid deficiency). due to the disease state. Other reasons are misconceptions related to enteral feeding in patients with abdominal disease Monitoring of Nutrition or measurable gastric residue. Variable content of kitchen Efforts to provide greater than 55- 60% of the target calorie feeds may also contribute to inadequate delivery of nutrients. requirement within 1st week of ice stay should be made in Involvement of the hospital dietician in routine care of ICU order to achieve clinical benefit. Tolerance of enteral feeding patents can avoid underfeeding. should be determined by looking for abdominal distension, pain, bloating, passage of stools, and monitoring gastric Refeeding syndrome is seen when full nutritional requirement residual volume. Reliance on gastric residual volumes alone is suddenly established in individuals with chronic severe is not an ideal method to monitor tolerance and overzealous malnutrition. Risk factors include body mass index (BMI) emphasis of the gastric residual volume has been proven to <16kg/m2, weight loss of >15% in 3-6 months, little or no hinder the achievement of daily calorie intake goals.10 Gastric nutrition in last 10 days, or low levels of phosphate, residue should be aspirated with a syringe every 6 hours; or prior to feeding. When adequate calories are volumes of up to 500 ml are acceptable, and propping up to provided to these patients, there is intracellular shift and 45%, addition of gastric prokinetic agents like erythromycin utilization with intracellular shift of phosphate, potassium, or metoclopramide and use of continuous feeding will improve magnesium and . This causes cardiovascular tolerance of enteral feeds.11 If high gastric residue persists in abnormalities like ventricular , left ventricular spite of these measures it is imperative to place the failure, pulmonary edema and shock. Muscle damage results in (endoscopically or otherwise) in the duodenum or jejunum as myopathy, rhabdomyolysis, respiratory weakness, dyspnoea intestinal motility is better preserved in critical illness than that and failure to wean from ventilation. Other manifestations of the stomach. Most patients receiving post-pyloric feeding include confusion, Wernicke’s encephalopathy, metabolic will not tolerate intermittent bolus feeding. Diarrhoea should acidosis, paresthesiae and tetany. Refeeding syndrome is be looked for in patient receiving enteral feeds and should prevented by starting with 5 to 10 kcal/kg/day, which is be evaluated to differentiate between infective and osmotic gradually increased to full requirements in 4-7 days. Cardiac etiology. rhythm should be closely monitored. Adequate provision of fluids, trace elements and vitamins, especially thiamine, In patients receiving parenteral nutrition, bedside blood is important. Intravenous supplementation of potassium, glucose monitoring should be performed several times a phosphate and magnesium is required. However, intravenous day. BUN, creatinine, electrolytes and bicarbonate should be phosphate is not available in India and enteral replacement monitored daily for the first few days. Phosphate, calcium, is done. magnesium and albumin are checked at least once a week. Clinical features of vitamin, trace element and essential fatty Complications of enteral nutrition are diarrhea, misplacement acid deficiency are now rarely seen since most enteral formulae of the feeding tube, blockage and failure to achieve the target

713 Medicine Update 2012  Vol. 22 contain adequate quantities of these nutrients. However, they Use of an enteral formulation fortified with fish oil may still be encountered if these are not supplemented in (which contains ω-3 fatty acid eicosapentaenoic acid and patients on parenteral nutrition. Obtaining trace element docosohexaenoic acid), borage oil (rich in gamma-linolenic mixtures for IV use is a particular problem in India. Onset acid), and antioxidants may reduce length of stay in the ICU of hepatic dysfunction may require decrease in the calories and improve survival in patients with acute lung injury and provided by the parenteral nutrition. ARDS by exerting an anti-inflammatory effect. Nutrition in special situations Conclusion Acute Renal Failure Nutrition is an important and often overlooked aspect of critical Unlike chronic kidney disease, patients with acute renal care. Over the last few years, several emerging concepts have failure do not require protein restriction. Most patients will be changed the role of nutrition from one of providing normal oliguric and calorie dense formulae may be required to provide daily requirement of nutrients and metabolic support to one adequate calories without causing fluid overload. Potassium where pharmacologic doses of nutritional supplements may restriction may be needed. Protein requirements may be as actually change the course and outcome of critical illnesses. high as 2.5 g/kg/day if the patient is receiving or While initial trails using pharmaconutrition have shown great continuous renal replacement therapy. promise, current research does not provide evidence for the routine use of these modalities in most critically ill patients Hepatic failure with shock, sepsis or organ failure. Randomized controlled Nutritional and protein requirements should be in keeping trials are in progress and their results may change the way that with standard requirements of ICU patients. Branch chain we provide nutrition to ICU patients in future. amino acids may be useful to reduce grade of in few References patients who do not respond to usual anti-encephalopathy 1. Petros S, Engelmann L. Enteral nutrition delivery and energy ex- measures. penditure in medical intensive care patients. Clin Nutr 2006;25:51- Pancreatitis and inflammatory bowel disease 59. All attempts to feed patients enterally, even in severe acute 2. Cerra FB, Benitez MR, Blackburn GL, Irwin RS, Jeejeebhoy K, Katz DP, et al. Applied nutrition in ICU patients. A consensus pancreatitis. In severe acute pancreatitis, enteral feeding statement of the American College of Chest Physicians. Chest through a nasogastric tube should be attempted as soon as fluid 1997;111:769-778. is complete. Feeding is initiated within 24 to 48 3. McClave SA, Martindale RG, Vanek VW, McCarthy M, Roberts hours and gradually increased over the next few days. The P, Taylor B, et al. Guidelines for the provision and assessment of likelihood of successful enteral feeding is greater with naso- nutrition support therapy in the adult critically ill patient: Society jejunal feeding and use of continuous feeding. In difficult of Critical Care Medicine (SCCM) and American Society for Par- cases switching protein to small peptide based nutrition, enteral and Enteral Nutrition (ASPEN). J Parenter Enteral Nutr and using medium chain triglycerides instead of long chain 2009;33:277-316. triglycerides may be helpful. In case enteral nutrition cannot 4. Boateng AA, Sriram K, Meguid MM, Crook M. Refeeding syn- be established for at least 5 days, parenteral nutrition needs drome: Treatment considerations based on collective analysis of to be started. literature case reports. Nutrition 2010;26:156-167. 5. Ziegler TR. Parenteral nutrition in the critically ill patient. N Eng Pharmaconutrients J Med 2009;361:1088-1097. Enteral glutamine is a conditionally essential 6. Qaseem A, Humphrey LL, Chou R, Snow V, Shekelle P for the which promotes gut mucosal integrity antioxidant defenses, Clinical Guidelines Committee of the American College of Phy- immune function, production of heat shock proteins, and sicians. Use of intensive insulin therapy for the management of nitrogen retention and may be helpful in trauma and burns. glycemic control in hospitalized patients: A clinical Practice Gui- deline from the American College of Physicians. Ann Intern Med Immune-modulating enteral formulations containing arginine, 2011;154:260-267. glutamine, nucleic acid and ω-3 fatty acids are useful for 7. Singer P, Berger MM, Van den Berghe G, Biolo G, Calder , For- patient population with major elective surgery, trauma, burns, bes A, et al. ESPEN Guidelines on Parenteral Nutrition: Intensive head and neck cancer, and critically ill patients on mechanical care. Clinical Nutrition 2009;28:387–400. ventilation. Arginine supplementation is known to cause 8. Bessey PQ. Metabolic response to critical illness. In: Souba WW, improvement in nitrogen balance and protein synthesis and Fink MP, Jurkovich GJ, Kaiser LR, Pearce WH, Pemberton JH, is also known to improve immunity parameters post stress Soper NJ (eds). ACS Surgery: Principles and practice 2005. and surgery. Arginine is best avoided in patients with severe WebMD Inc, New York: pp 1539-1565. sepsis as it may worsen hemodynamics by increasing nitric 9. Bistrian BR. Enteral and parenteral nutrition therapy. In: Longo oxide production. DL, Kasper DL, Jameson JL, Fauci AS, Hauser SL, Loscalzo J. Harrison’s Principles of . 18th Ed: 2012. Mc- Graw-Hill. 714