Medical Nutrition Therapy for Metabolic Stress and Critical Care Objectives • Describe the metabolic response to critical illness • Describe role of nutrition therapy for critically ill patients • Describe how to assess nutrient needs for a critically ill patient Metabolic Stress • Stressors: – Sepsis – Surgery – Trauma (includes burns) • These stressors activate a particular systemic response, leading to a number of physiologic and metabolic changes What happens during metabolic stress? • Metabolic alterations to meet the body’s needs for survival – hypermetabolism – hypercatabolism – hyperglycemia – sodium & water retention – increased heart rate & cardiac output – hypercoagulability & increased platelet aggregation – increased sympathetic tone • controls “fight or flight” response Metabolic Response to Stress • Involves most metabolic pathways • Accelerated metabolism of lean body mass • Negative nitrogen balance • Muscle wasting Hypercatabolism! Ebb Phase • Usually restricted to the first 24-48 hours • Immediate response – – – – – Hypovolemia and tissue hypoxia Decreased cardiac output Decreased oxygen consumption Lowered body temperature Decreased insulin and increased glucacon levels Flow Phase • Follows fluid resuscitation and improved O2 transport • Increased cardiac output begins • Increased body temperature • Increased energy expenditure • Total body protein catabolism begins •  glucose production, free fatty acids, circulating insulin, catecholamines, glucagon, & cortisol Figure 89.2 Neuroendocrine and metabolic consequences of injury ACTH, adrenocorticotropic hormone From: Lowry SF & Perez JM The hypercatabolic state In Shils ME, et al (eds) Modern Nutrition in Health & Disease Lippincott, Williams & Wilkins, 2006 Metabolic Responses During Sepsis Organ Liver Response  Glucose production  Amino acid uptake  Acute-phase protein synthesis  Trace metal sequestration Central nervous system Circulation Anorexia, fever  Glucose  Triglycerides  Amino acids  Urea  Iron  Zinc Metabolic Responses During Sepsis (continued) Skeletal muscle  Amino acid efflux (especially glutamine), Intestine  Amino acid uptake from both luminal and leading to loss of muscle mass circulating sources, leading to gut mucosal atrophy Endocrine  Adrenocorticotropic hormone  Cortisol  Growth hormone  Epinephrine  Norepinephrine  Glucagon  Insulin initially, then  levels & insulin resistance From Michie HR: Metabolism of sepsis and multiple organ failure, World J Surg 20:461, 1996 Fat • Can be immunosuppressive, so don’t overfeed – Especially IV fat emulsion • Provide anywhere between 15-40% of kcals as fat – Depends on route of feeding & type of formula selected • Type of fat may make a difference Omega-3 Fatty Acids • In animal models, a high fish oil diet leads to – Decreased PGE2 release – Improved cellular immunity • In humans – Decreased PGE2 production in ill patients – In patients with inflammatory conditions (e.g rheumatoid arthritis, Crohn’s disease), fish oil supplementation has been shown to be helpful in some studies – Studies in the critically ill population have shown mixed benefit Vitamins, Minerals, Trace Elements • Grade B evidence for providing antioxidant vitamins and trace minerals (especially selenium) – Optimal dose & route not defined! • So if you are tube feeding, make sure that the patient is getting 100% of the RDIs for vitamins & minerals – Consider an additional vitamin/mineral supplement? • Monitor electrolytes by serum levels – Assure normal phosphate level Nutrition Recommendations for Specific Populations MNT for SIRS and MODS • Goals – Minimize “autocanibalism” – Prevent or correct specific nutrient deficiencies – Provide adequate kcals and protein – Manage fluid and electrolytes – Begin nutrition support as soon as hemodynamically stable • Nutrition support alone cannot abolish hypermetabolism Special Considerations for ARDS/ALI • Careful assessment of nutritional status • How does underlying disease affect needs • Goals of therapy: – – – – – – Meet basic nutritional needs Preserve LBM Restore respiratory muscle mass & strength Maintain fluid balance Improve immune function Facilitate weaning from mechanical ventilation Special Considerations for ARDS/ALI (continued) • These patients are often hypermetabolic & hypercatabolic – Avoid excessive energy delivery • Indirect calorimetry is best • Some use BEE x 1.2-1.4 if IC is not available – Protein delivery based on illness, medications • Typically start with 1.5 g/kg, max of g/kg • Fluid restriction if volume overloaded • Optimize potassium, magnesium, and phosphate levels • Meet RDIs for vitamins & minerals Special Considerations for Critically-ill Obese Patients • “Permissive Underfeeding” – BMI > 30 kg/m2: • 11-14 kcal/kg actual weight, or • 22-25 kcal/kg ideal body weight • Research done at Brigham and Women’s Hospital: – BMI 30-50, use 11-14 kcal/kg actual weight; BMI > 50, use 2225 kcal/kg IBW – Protein delivery needs to be high: • g/kg IBW for class I and class II obesity • 2.5 g protein/kg IBW for class III • Remember, indirect calorimetry is best, if you have it available to you Special Considerations for Critically-ill Obese Patients (continued) • Once out of the ICU – Transition to provide somewhat more calories and less protein – Depends on clinical status upon transfer out of the ICU – Do not pursue weight loss until the acute illness is resolved For Patients Receiving Continuous Renal Replacement Therapy • Protein losses are high – Estimate needs between 1.8-2.5 g/kg – Do not restrict protein! • There are high water-soluble vitamin losses and need repletion – 100 mg thiamin – mg folate – 250 mg ascorbic acid For Patients with Liver Disease • Avoid protein restriction – Meet protein needs for critical illness – No need for branched chain amino acids • May need a fluid restriction • Can be tube fed safely if no severe GI bleeding For Severe Pancreatitis • Once fluid resuscitated, insert a nasoenteric feeding tube for early enteral nutrition • Can try gastric feeding first • Transition to jejunal feedings if poorly tolerated • Parenteral nutrition after all efforts to promote enteral tolerance fail – Wait at least days to start parenteral nutrition Medical Nutrition Therapy for Acute Pancreatitis • Energy requirements: – Typically 25-35 kcal/kg • Lower end for mild pancreatitis, upper end for severe pancreatitis – Some references say up to 1.5 x basal energy expenditure for severe pancreatitis • Protein requirements – Range: 1.2-1.5 g/kg – Use the lower end for mild pancreatitis, the upper end for severe pancreatitis Summary • Nutrition support is essential for critically ill patients • Early nutrition assessment and feeding is beneficial to minimize loss of lean body mass, help improve weaning from the ventilator, and improve outcomes Selected References • • • • • McClave SA et al Guidelines for the provision and assessment of nutrition support therapy in the adult critically ill patient: Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.) J Parenter Enteral Nutr 2009; 33:277-316 Mogensen KM, Corona JC, Robinson MK Validation of the American Society for Parenteral and Enteral Nutrition recommendations for caloric provision to critically-ill obese patients with indirect calorimetry JPEN J Parenter Enteral Nutr 2011;35:135-136 (Abstract S31-4) The NICE-SUGAR Study Investigators Intensive versus conventional glucose control in critically ill patients N Engl J Med 2009; 360:1283-1297 Ware LB, Matthay MA The acute respiratory distress syndrome N Engl J Med 2000;342:1334-1349 Cook DJ, Heyland DK Pharmaconutrition in acute lung injury JAMA 2011;306:1599-1600