Refeeding Syndrome
Definition
Refeeding syndrome is a potentially fatal metabolic complication that occurs after rapid reintroduction of nutrition (especially carbohydrates) in malnourished or starved patients, characterized by acute shifts of phosphate, potassium, magnesium, fluids, and vitamins (notably thiamine) due to insulin surge.
Core hallmark: Hypophosphatemia after refeeding.
Pathophysiology
1️⃣ Starvation State
- ↓ Insulin, ↑ glucagon, cortisol
- Energy from fatty acids & ketones
- Intracellular depletion of:
- Phosphate
- Potassium
- Magnesium
- Serum levels may appear normal
2️⃣ Refeeding (Especially Carbohydrates)
- ↑ Glucose → ↑ Insulin surge
- Insulin drives:
- Glucose + phosphate + K⁺ + Mg²⁺ into cells
- ↑ ATP synthesis → ↑ phosphate utilization
- Result → rapid extracellular depletion
3️⃣ Additional Effects
- Sodium & water retention → edema, heart failure
- Thiamine deficiency worsens → lactic acidosis, Wernicke encephalopathy
Key Electrolyte & Metabolic Abnormalities
|
Abnormality |
Mechanism |
Clinical Impact |
|
Hypophosphatemia (MOST IMPORTANT) |
ATP generation, glycolysis |
Respiratory failure, hemolysis, rhabdomyolysis, arrhythmias |
|
Hypokalemia |
Insulin-mediated intracellular shift |
Arrhythmias, ileus |
|
Hypomagnesemia |
Cellular uptake |
Refractory hypokalemia, arrhythmias |
|
Thiamine deficiency |
Increased carbohydrate metabolism |
Wernicke encephalopathy, lactic acidosis |
|
Fluid overload |
Na⁺ retention |
Heart failure, pulmonary edema |
|
Hyperglycemia |
Insulin resistance |
Osmotic diuresis |
Who Is at Risk?
High-Risk Groups
- Prolonged starvation (>5–7 days)
- BMI <18.5 kg/m²
- Unintentional weight loss >10–15%
- Chronic alcoholism
- Anorexia nervosa
- Cancer / chemotherapy
- Post-operative patients
- Chronic liver disease
- Uncontrolled diabetes
- Elderly, ICU long-stay
NICE Criteria – High Risk
- One of:
- BMI <16
- Little/no intake >10 days
- Weight loss >15% in 3–6 months
OR - Two of:
- BMI <18.5
- No intake >5 days
- Alcohol misuse
- Low baseline electrolytes
Clinical Manifestations
Timeline
- Typically within 24–72 hours after refeeding
(can occur up to 5 days)
Systems Involved
Cardiovascular
- Arrhythmias
- Heart failure
- Hypotension
- Sudden cardiac death
Respiratory
- Respiratory muscle weakness
- Failure to wean from ventilator
Neurological
- Confusion, delirium
- Seizures
- Wernicke encephalopathy
Hematologic / Muscular
- Hemolysis
- Rhabdomyolysis
- Weakness, myopathy
Diagnosis
Clinical diagnosis
Suspect RFS when:
- Malnourished patient
- Recently started feeding
- Develops ↓ phosphate ± K⁺/Mg²⁺
Diagnostic Clue
Hypophosphatemia occurring after initiation of nutrition
Prevention
Before Feeding
- Check:
- Phosphate
- Potassium
- Magnesium
- Glucose
- Give:
- Thiamine 100–300 mg IV/PO
- Multivitamins
Start Feeding SLOW
|
Risk Level |
Calories |
|
High risk |
5–10 kcal/kg/day |
|
Moderate risk |
10–20 kcal/kg/day |
- Prefer low-carbohydrate initially
- Avoid rapid glucose infusion
Monitoring (ICU STANDARD)
- Daily (or 12-hourly initially):
- Phosphate
- Potassium
- Magnesium
- Fluid balance
- ECG monitoring
Management
1️⃣ Stop / Reduce Feeding
- Temporarily halt or reduce calories
2️⃣ Correct Electrolytes Aggressively
- Phosphate (IV if severe)
- Potassium
- Magnesium
3️⃣ Thiamine Replacement
- 100–300 mg/day (IV preferred in ICU)
4️⃣ Restart Nutrition Slowly
- Gradual escalation over 4–7 days