Refeeding Syndrome

Potentially fatal shifts in fluids and electrolytes that may occur in malnourished patients receiving artificial feeding.

Background/Epidemiology

• During prolonged fasting, there are several changes that occurs in the body:
  • Net effect is a switch from carbohydrate metabolism to protein/fat metabolism and a decrease in basal metabolic rate by up to 25%
    • Muscle/liver switch from using ketones to use fatty acids as their source of energy
    • Brain then switches from glucose to ketone utilisation
    • Liver decreases rate of gluconeogenesis to preserve muscle protein
  • Intracellular minerals are depleted, however serum levels often remain normal.
    • Renal excretion of fluid/minerals also reduces
• During re-feeding
  • glycaemia causes insulin release and decreased release of glucagon, stimulating glycogen, fat and protein synthesis.
    • requiring minerals and vitamins
  • insulin also stimulates the uptake of minerals e.g. K+, PO4+ and Mg2+ into the cells.
    • water follows
    • minerals are already depleted and serum levels rapidly drop
      • the hallmark of refeeding syndrome is hypophosphataemia, although a change in a range of fluid/electrolytes can be seen
• Incidence/prevalence is not really known, but there is around a 0.4% incidence of severe hypophosphataemia- with malnutrition being the commonest cause.

Conditions increasing risk for RFS

• Anorexia Nervosa
• Chronic alcoholism
• Cancer patients
• Post-op patients
• Elderly patients- with comorbidity
• Uncontrolled diabetes
• Chronic malnutrition
  • Marasmus (severe malnutrition)
  • Prolonged fasting or a low energy diet
  • Morbid obesity with profound weight loss
  • High stress patient unfed for >7 days
  • Malabsorptive syndromes e.g. Inflammatory bowel disease, chronic pancreatitis, cystic fibrosis, short bowel syndrome
• Long term users of antacids, diuretics

Assessment

• Patients with one or more of
  • BMI <16
  • Unintentional weight loss >15% in the past 6 months
  • Little or no nutritional intake for >10 days
  • Low levels of potassium, phosphate or magnesium before feeding
• OR two or more of
  • BMI <18.5
  • Unintentional weight loss >10% in the last 6 months
  • Little or no nutritional intake for >5 days
  • History of alcohol/drug misuse, or drug use including insulin, chemotherapy, antacids or diuretics
• …. are at risk of refeeding syndrome

So check BMI and U&Es (minimum) prior to re-feeding.

Management

• Prior to re-feeding- administer thiamine (200-300mg daily, vitamin B and other trace elements with supplements daily
• Start feeding slowly and slowly (no more than 50% of the energy requirements- recommended at 0.0418MJ/kg/day) increase over 4-7 days.
• Monitor fluid and electrolyte balance and supplement/correct these appropriately
  • Normal levels of potassium (3.6-5mmol/L); normal intake 2.6-4mmol/L
  • Normal levels of calcium (2.1-2.55mmol/l)
  • Normal levels of phosphate (0.8-1.45mmol/l); normal intake 0.3-0.6mmol/l
  • Normal levels of magnesium (0.7-1mmol/l); normal intake 0.2-0.4mmol/l

Potential complications

Refeeding syndrome can affect almost every organ system, due to a mixture of electrolyte disturbances.

• Serious complications include arrhythmias and cardiac arrest, pulmonary oedema and respiratory failure, seizures/fits, renal failure, metabolic acidosis/ketosis, amongst other things
• For a longer list, see here
• These complications often require management in their own right, some of which can worsen other problems.  Prevention of refeeding syndrome is, therefore, the main goal, rather than treatment.