A critically ill patient in surgical ICU has been nil by mouth for 7 days on parenteral nutrition. Serum phosphate drops to 0.4 mmol/L (normal 0.8–1.45) and the patient develops respiratory failure and cardiac arrhythmias. What is this syndrome and which electrolyte is the primary driver?

• A Hyperosmolar hyperglycaemic state; glucose
• B Hypomagnesaemia from TPN; magnesium
• C Refeeding syndrome; phosphate (hypophosphatemia) ✓
• D Thiamine deficiency (Wernicke's); B1

Explanation

Refeeding syndrome occurs when malnourished patients are rapidly introduced to carbohydrate-rich nutrition (enteral or parenteral) after a period of starvation. Insulin release stimulates cellular uptake of phosphate, potassium, and magnesium, causing acute extracellular depletion. Hypophosphatemia is the hallmark and primary driver of clinical features: respiratory muscle weakness (failure to wean), cardiac arrhythmias, hemolytic anemia, and neurological dysfunction. NICE guidelines recommend identifying at-risk patients (BMI < 18.5, minimal intake > 5 days) and replacing phosphate before and during refeeding, with gradual caloric escalation (start at 10 kcal/kg/day, increase over 4–7 days).

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.