Refeeding syndrome

Overview
Refeeding Syndrome was first observed in prisoners in the Far East at the end of World War II. Following prolonged starvation, the resumption of food precipitated cardiac failure & death. It is defined as a syndrome of "severe electrolyte and fluid shifts associated with metabolic abnormalities in malnourished patients undergoing refeeding, whether orally, enterally or parenterally".

Causes
Refeeding in these patients/circumstances:
 * anorexia nervosa
 * alcoholics
 * diabetic ketoacidosis
 * morbidly obese after massive weight loss
 * chronic gastrointestinal disese
 * neurological dysphagia
 * post-operatively, e.g. ileus

Pathophysiology
In starvation or effective starvation, the body becomes dependent on the breakdown of endogenous fats and proteins. At the same time, due to poor intake, the total body stores of several essential electrolytes are depleted, namely phosphate, potassium and magnesium. Although serum levels are often low, serum levels can sometimes be maintained.

When feeding is resumed, there is a sudden large load of carbohydrate. The insulin that is secreted in response to this drives potassium and phosphate into cells. The serum levels of both electrolytes, often already low to being with, fall precipitously.

Many of the cellular ion pumps which normally maintain intra-cellular electrolyte levels are down-regulated in the starving state. These pumps normally pump phosphate, potassium and magnesium into the cells. In refeeding, the ion transporters are upregulated leading to depletion of serum levels of the above electrolytes..

The ensuing hypophosphatemia, hypokalemia and hypomagnesemia predispose to cardiac arrhythmias. Cardiac failure is sometimes precipitated by fluid retention, another not completely explained phenomenon observed in refeeding syndrome.

a==Clinical Features==

Hypophosphatemia is characteristic, with levels typically under 0.65mmol/l but severe cases are under 0.35mmol/l. Levels can fall within a few hours of refeeding, but the highest risk is seen in the first week. Hypokalemia, hyponatremia and hypomagnesemia are variable.
 * fluid retention
 * electrolyte disturbance
 * Congestive heart failure and cardiomyopathy due to myonecrosis
 * cardiac arrhythmia
 * sudden death
 * delirium - typically developing a week after refeeding, lasting a few days. May be convulsions.
 * mild rises in liver function tests

Clinical Approach

 * Pre-empt - identify malnourished patients
 * Monitor electrolytes and replace as appropriate
 * check levels both before and during feeding as serum levels may be normal despite depletion of total body stores; levels only fall as feeding starts
 * phosphate
 * potassium
 * magnesium


 * Gentle refeeding, starting at 75% of requirements and building up over 3-5 days
 * If symptoms of refeeding syndrome, stop feeding (eg stop TPN) or reduce to 50-75% requirements, and supplement phosphate.