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Refeeding Syndrome The sudden restoration of nutrient intake, especially carbohydrates, in patients with severe malnutrition suddenly reactivates a number of dormant metabolic pathways. Lack of key micronutrients, especially thiamine and other B-complex vitamins, causes glucose to be converted to lactate rather than go through oxidative phosphorylation. The sudden availability of carbohydrates exceeds cell demands, necessitating energy-requiring fat production and leading to a further energy deficit. In addition, there is a shift of the previously depleted electrolytes potassium, phosphorus, and magnesium back into cells, resulting in potentially severe hypokolemia, hypomagnesemia and hypophosphatemia. These compounds must be provided at the rate of their shift into the intracellular compartment. |
A. Enteral Support
The most beneficial route of nutrition is the enteral route, which is usually the only route available to outpatients or chronic care patients. The parenteral route is usually only required for the acutely ill or injured hospital patient with catabolic disease. If prior malnutrition has resulted in intestinal mucosal atrophy and malabsorption is present, supplemental glutamine, 10 to 20 g/d, should be provided along with an elemental diet or protein hydrolysate until mucosal function improves.
Oral intake of food is rarely sufficient to meet either energy or protein needs in a catabolic or malnourished patient. Tube feeding or nutrient supplements are invariably necessary.
Tube Feeding: The tube feeding approach is often the first used until the catabolic insult begins to resolve and the patient is capable of taking adequate oral nutrition. There is a large variety of tube feeding solutions available to meet requirements for different clinical disease states. Most are somewhat hyperosmolar and water may be added to increase gastrointestinal tolerance. The nutrient mix is typically 55% to 65% carbohydrates, 25% fat, and 20% protein. Most tube feeding solutions have high energy (calorie) and moderate protein contents, with a calorie-to-nitrogen ratio of 150:1, which is insufficient protein to correct catabolism or malnutrition in patients with a wound. The increased fat content of most high-energy supplements can lead to impaired gastric emptying, necessitating placement of a postpyloric tube. The increased carbohydrate content can lead to hyperglycemia in the elderly or the diabetic population. Typical tube feeding solutions can be used to reach energy and protein goals, but poor palatability make these goals unachievable through oral consumption. Therefore, the switch from tube feeding to normal food and supplemental nutrients is difficult, unless they are palatable and well tolerated by the patient.