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Nutrition in ICU

3. The refeeding syndrome

This is an under-recognised complication of nutritional support in critical care that can cause considerable morbidity and mortality. Feeding severely malnourished patients initiates a shift from the fatty acid metabolism of starvation back to carbohydrate metabolism with increased phosphate and thiamine requirements, causing acute thiamine deficiency, release of insulin, and an intracellular shift of potassium, magnesium, and phosphate.

At risk patients should be identified prior to feeding.


Patients at risk of developing Refeeding Syndrome:

Any ICU patient with one of the following is at risk of developing refeeding syndrome:

  • BMI < 16 kg/m2
  • Unintentional weight loss greater than 15% within the last 3-6 months
  • Little or no nutritional intake for more than 10 days
  • Critically low levels of potassium (<2.5mmol/l, phosphate <0.32mmol/l or magnesium < 0.5mmol/l) prior to feeding

OR any patient with two or more of the following:

  • BMI less than 18.5 kg/m2
  • Unintentional weight loss greater than 10% within the last 3-6 months
  • Little or no nutritional intake for more than 5 days
  • A history of alcohol abuse or drugs including insulin, chemotherapy, antacids or diuretics (contribute to low electrolyte levels).

Refeeding syndrome may not present as a clear diagnosis; it may contribute to the patient’s critical illness and go unrecognised.

The recently published NICE Guidelines for Nutritional Support recognise the problem and suggest ways to recognise patients at risk and introduce nutritional support with extra care.

Features of Refeeding Syndrome

Caused by

Cardiac failure, hypotension, diarrhoea, arrhythmias, seizures, immune dysfunction, respiratory muscle weakness, rhabdomyolsysis

and hypokalaemia,

Extracellular fluid expansion:
peripheral and pulmonary oedema

Sodium retention due to
insulin release,
fluid shifts.

Lactic acidosis, coma, neurological damage
(Wernicke’s encephalopathy and/or Korsakoff’s psychosis), cardiac failure

Thiamine deficiency


NICE recommendations for nutrition in patients at high risk of developing refeeding syndrome

Start nutrition support at a maximum of 10 kcal/kg/day, increasing levels slowly to meet or exceed full needs by 4-7 days

Use only 5 kcal/kg/day in extreme cases and monitoring cardiac rhythm continually in these people and any others who already have or develop any cardiac arrhythmias

Restore circulatory volume and monitoring fluid balance and overall clinical status closely

Provide 30 minutes before and during the first 10 days of feeding: Full dose daily intravenous vitamin B preparation (Pabrinex) or Oral thiamine 200-300mg daily and a balanced multivitamin/trace element supplement once daily.

Provide potassium supplements (2-4 mmol/kg/day), phosphate (0.3-0.6 mmol/kg/day) and magnesium (0.2mmol/kg/day iv, 0.4 mmol/kg/day oral) unless pre-feeding levels are high.

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