Expansion
Insulin drives phosphate, potassium and magnesium into cells
Expansion
Mechanism
- Prolonged starvation depletes intracellular phosphate, potassium and magnesium, though serum levels may be normal
- Carbohydrate refeeding triggers a surge of insulin
- Insulin drives glucose, phosphate, potassium and magnesium into cells
- Serum levels fall abruptly
- Thiamine, already depleted, is consumed rapidly as a cofactor in carbohydrate metabolism
- Sodium and water retention adds fluid overload
Consequences: hypophosphataemia causing muscle weakness, respiratory failure, cardiac failure, rhabdomyolysis, haemolysis and confusion; arrhythmias from potassium and magnesium shifts; Wernicke encephalopathy; and cardiac decompensation from fluid overload in an atrophied myocardium.
At risk: body mass index under 16, unintentional weight loss over 15 per cent, little intake for more than 10 days, alcohol dependence, anorexia nervosa, and low baseline electrolytes.
Prevention: start at no more than 10 kcal/kg/day (5 in extreme cases), give thiamine and B vitamins before feeding, replace electrolytes proactively and monitor daily.