Case Studies 1

Case 1: Parenteral Nutrition

The Nutrition Support Team is consulted on a 35-year-old man with a history of Crohn’s disease 8 days status/post abdominal surgery. The patient had undergone resection of a severely inflamed portion of ileum (~ 4 feet) following several weeks of intermittent fever, abdominal pain and bloody diarrhea, poorly responsive to medical management. Persistent postoperative intestinal ileus has prevented enteral feeding. He is being treated with antibiotics for an abdominal wound infection.

Current body weight is 55 kg, usual weight (6 months ago) was 65 kg, and ideal body weight for height is 70 kg. He has lost 7 kg over the past 2-3 weeks. Prednisone (20 mg/day) was initiated 6 months ago during a previous flare of his disease and he has remained steroid-dependent since that time. For several weeks prior to admission, the patient was eating poorly (< 25-50% of usual intake) due to abdominal pain and diarrhea exacerbated by oral diet. PMH is otherwise unremarkable. Current medications include intravenous hydrocortisone 50 mg every 8 hrs and ciprofloxacin.

Physical examination reveals a temperature of 39˚C, evidence of abdominal wound cellulitis, moderate abdominal distention and tenderness, and no bowel sounds. He exhibits mild skeletal muscle and fat wasting. No evidence of skin rash, glossitis, hair loss, or other overt signs of micronutrient deficiency. The patient has been receiving only intravenous hydration fluid (5% dextrose with potassium) since the operation. Laboratory tests are normal with the exception of a blood glucose level of 200 mg/dl, a magnesium level of 1.1 mEq/L (normal range 1.5 – 2.0), a potassium level of 3.2 mEq/L (normal range 3.5 to 4.5) and moderate leukocytosis.

Question 1: What is the evidence for malnutrition in this patient?

1. Generalized malnutrition is present as evidenced by: 1) his weight loss pattern, and current weight as percent of ideal body weight (79% of IBW); 2) history of poor dietary intake for several weeks in addition to provision of only hydration fluids since operation; 3) evidence of muscle and fat wasting on PE; 4) available blood tests suggesting likely magnesium and potassium depletion. Given his history of poor food intake, weight loss and diarrhea, he may also be depleted in zinc and several other micronutrients, despite the lack of classical PE findings. Blood levels of specific nutrients are needed for confirmation.

Question 2: What factors likely contributed to loss of skeletal muscle mass?

1. In addition to poor dietary intake of protein and energy, chronic inflammation due to Crohn’s disease and the acute stress of a major operation and wound infection will induce accelerated breakdown of lean tissue, due, in part, to catabolic hormonal and cytokine signals (e.g. increased levels of glucagon, catecholamines and cortisol in blood and interleukins and tumor necrosis factor in blood and tissues). Chronic prednisone administration also favors protein breakdown. Nitrogen balance in this patient will be markedly negative.

Question 3: What are likely causes for the low serum magnesium and potassium levels and the elevated blood glucose concentration in this patient without a history of diabetes? What are possible consequences of these abnormalities?

1. Low electrolytes are likely due to decreased dietary intake and increased stool losses (diarrhea). Magnesium is not being administered in hydration fluids postoperatively. Elevated blood glucose is due to resistance to insulin action associated with catabolic stress (infection, inflammation, operation) and administration of corticosteroids. Decreased electrolyte levels may induce intestinal ileus, and if levels are very low, cardiac dysfunction and arrhythmias. Hyperglycemia of this degree may inhibit immune cell function and predispose the patient to infection.

Question 4: What are potential consequences of generalized malnutrition in this individual?

1. Protein-energy malnutrition is associated with increased risk of infection due to decreased lymphocyte number and/or function, poor wound healing, muscle fatigue, organ dysfunction and prolonged convalescence.

Question 5: Should nutritional support be instituted, and if so, how should this be accomplished?

1. Yes, given the significant weight loss, prolonged poor dietary intake plus eight days of hydration fluid only and catabolic stress (operation, fever, and wound infection, steroid treatment). Intravenous feeding must be instituted because the intestinal tract is not functional due to ileus; thus, enteral feedings cannot be used at this point. Blood glucose should be controlled with insulin prior to institution of intravenous feeding. Intravenous protein intake should be given at ≈ 1.2-1.5 g/kg/day. Adequate energy should be provided (as dextrose primarily, but lipid emulsion may be used for energy and to prevent essential fatty acid deficiency) to ensure efficient utilization of protein for anabolism (see below). Insulin is added as needed to maintain normal blood glucose levels. Adequate electrolytes should be administered, guided by serial serum values. Standard amounts of intravenous vitamins and trace elements should also be administered. Consideration should be given to empiric provision of extra zinc given his abdominal wound and history of diarrhea, which will increase body zinc losses. Supplemental vitamin C will help wound healing in cases of vitamin C depletion and are often used empirically in this setting.

Question 6: Given his current nutritional state, what metabolic complications may result from aggressive refeeding?

1. Hyperglycemia (unless blood glucose is controlled at initiation and adequate insulin is given as needed during therapy)
2. Refeeding syndrome , characterized by a rapid decrease in serum potassium, magnesium and especially phosphorus (primarily due to insulin-induced intracellular shift and phosphorus utilization in ATP generation, coupled with decreased body stores due to malnutrition), thiamine depletion (use in CHO and energy metabolism coupled with prior dietary deficiency), and in severe cases, peripheral edema (insulin-induced sodium retention or high-output heart failure due to thiamine depletion), arrhythmia (due to low electrolyte levels), and congestive heart failure (iv fluid given in setting of malnutrition-induced cardiac muscle atrophy, increase in metabolic rate due to nutrient metabolism).