Gastrointestinal · Year 2 · from Gastrointestinal

Case 2: Refeeding Syndrome

Patient Presentation

Demographics: 19-year-old female

Chief Complaint: Admitted for severe malnutrition; now with new weakness and confusion on hospital day 3

History of Present Illness: The patient was admitted 3 days ago for severe malnutrition in the context of anorexia nervosa. She reports progressively restrictive eating over 2 years with minimal caloric intake for the past 3 months (estimated 200-400 kcal/day). On admission, she weighed 38 kg (BMI 14.2) and was bradycardic and hypothermic. She was started on nasogastric tube feeding yesterday at 1800 kcal/day.

Today (hospital day 3), she developed profound weakness, difficulty breathing, confusion, and palpitations. The nursing staff noted new pedal edema and decreased urine output.

Past Medical History: Anorexia nervosa (diagnosed age 16), depression, amenorrhea for 14 months

Social History: College student, lives with parents

Physical Examination

On Admission (Day 1):

  • Vital Signs: BP 88/52, HR 42 bpm, Temp 35.6C
  • BMI: 14.2 (severely underweight)
  • Cachectic female with temporal wasting, loss of subcutaneous fat, visible ribs

On Hospital Day 3 (when symptoms developed):

  • Vital Signs: BP 98/60, HR 118 bpm (new tachycardia), RR 28/min (tachypnea)
  • General: Confused, weak, unable to lift arms against gravity
  • Cardiovascular: Tachycardic, no murmurs, JVD present
  • Respiratory: Bilateral crackles at lung bases
  • Extremities: 2+ pitting edema bilaterally (new)
  • Neurologic: Confused, disoriented; positive Chvostek sign

Workup and Results

On Admission:

  • Phosphorus: 2.8 mg/dL (low-normal)
  • Potassium: 3.4 mEq/L (low-normal)
  • Magnesium: 1.7 mg/dL (low-normal)
  • Glucose: 58 mg/dL

On Hospital Day 3:

  • Phosphorus: 0.8 mg/dL (critically low; normal 2.5-4.5)
  • Potassium: 2.1 mEq/L (critically low)
  • Magnesium: 1.0 mg/dL (low)
  • Glucose: 165 mg/dL
  • BNP: 890 pg/mL (elevated; fluid overload)
  • ECG: Sinus tachycardia, prolonged QT interval, flattened T waves, U waves (hypokalemia pattern)
  • Chest X-ray: Pulmonary edema, small bilateral pleural effusions

Diagnosis

Refeeding Syndrome with:

  • Severe hypophosphatemia
  • Severe hypokalemia
  • Hypomagnesemia
  • Fluid overload and pulmonary edema
  • Cardiac stress (tachycardia, QT prolongation)
  • Muscle weakness

Clinical Correlation

Refeeding syndrome is a potentially fatal metabolic complication occurring when malnourished patients receive nutritional repletion. This case demonstrates classic pathophysiology:

Why This Happened:

  1. During Starvation:
  • Insulin secretion decreases; body shifts to fat/protein catabolism
  • Intracellular phosphorus, potassium, and magnesium stores become depleted
  • Serum levels may appear normal (shift from intracellular to extracellular)
  • Thiamine stores are depleted
  1. Upon Refeeding (especially carbohydrate-rich):
  • Insulin surges in response to glucose/carbohydrate load
  • Insulin drives glucose into cells for glycolysis
  • Critically: Insulin also drives K+, Mg2+, and PO4 into cells
  • Precipitous drop in serum levels as already-depleted cells take up minerals
  • Increased metabolic demand for thiamine (cofactor in carbohydrate metabolism)

Consequences of Severe Hypophosphatemia:

  • Phosphorus is essential for ATP synthesis, 2,3-DPG (oxygen delivery), cell membranes
  • Respiratory failure: Diaphragm weakness (ATP depletion)
  • Cardiac failure: Impaired contractility
  • Rhabdomyolysis: Muscle breakdown
  • Hemolysis: Membrane instability, decreased 2,3-DPG

Why She Developed Fluid Overload:

  • Refeeding causes sodium and water retention (insulin effect)
  • Malnourished heart cannot handle volume load
  • Leads to pulmonary edema and peripheral edema

Risk Factors (This Patient Had Multiple):

  • BMI < 16
  • Minimal intake for > 10 days
  • Weight loss > 15% in 3-6 months
  • History of anorexia nervosa

Treatment

Immediate Management:

  • STOP enteral feeds temporarily
  • IV Phosphorus replacement: Sodium or potassium phosphate 15-30 mmol IV over 4-6 hours with cardiac monitoring
  • IV Potassium replacement: Target K+ > 3.0 mEq/L with continuous ECG monitoring (QT prolongation risk)
  • IV Magnesium replacement: 2-4 g IV over 2-4 hours
  • Thiamine 200-300 mg IV - should have been given BEFORE any feeding was initiated
  • Fluid restriction and diuresis for pulmonary edema
  • Telemetry monitoring

Resumption of Feeding (after electrolytes stabilize):

  • Restart feeding at very low rate: 5-10 kcal/kg/day
  • Advance slowly: Increase by 5 kcal/kg/day every 1-2 days
  • Target: Reach full caloric goal over 7-10 days
  • Monitor electrolytes twice daily for first week

Prevention Protocol (What Should Have Happened):

  1. Identify high-risk patients (BMI < 16, minimal intake, significant weight loss)
  2. Check baseline electrolytes and correct before feeding
  3. Give thiamine 200-300 mg BEFORE first feeding and continue for 3+ days
  4. Start feeds at 10-20 kcal/kg/day (NOT full caloric needs)
  5. Advance slowly over 5-7 days
  6. Monitor electrolytes daily (or twice daily in highest risk)
  7. Supplement phosphorus, potassium, magnesium prophylactically

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