How do you avoid refeeding syndrome in a patient with anorexic nervosa?

Preventing Refeeding Syndrome in Anorexia Nervosa

Start thiamine 200-300 mg IV daily before initiating any nutrition, begin feeding at 5-10 kcal/kg/day in severely malnourished patients (<70% ideal body weight), and aggressively supplement phosphate (0.3-0.6 mmol/kg/day), potassium (2-4 mmol/kg/day), and magnesium (0.2 mmol/kg/day IV or 0.4 mmol/kg/day orally) while monitoring electrolytes daily for the first 72 hours. 1, 2, 3

Pre-Feeding Protocol (Mandatory Before Starting Nutrition)

Thiamine administration is absolutely critical and must precede any caloric intake:

• Administer thiamine 200-300 mg IV daily starting before any feeding begins 3
• Continue thiamine for a minimum of 3 days, then maintain at 50 mg daily until adequate oral intake is established 4
• Provide full B-complex vitamins IV simultaneously with thiamine throughout the refeeding period 3
• Never initiate feeding without prior thiamine, as carbohydrate loading in thiamine-deficient patients precipitates Wernicke's encephalopathy, Korsakoff's syndrome, acute heart failure, and sudden death 1, 3

Baseline electrolyte assessment:

• Check phosphate, potassium, magnesium, and calcium levels before starting nutrition 3
• Correct severe electrolyte deficiencies, but recognize that massive intracellular deficits cannot be fully corrected without simultaneous feeding 3

Risk Stratification

Very high-risk patients (require most conservative approach):

• BMI <16 kg/m² or <70% ideal body weight 1, 3, 5
• Unintentional weight loss >15% in 3-6 months 2, 3
• Little to no nutritional intake for >10 days 2, 3
• History of chronic alcoholism 4, 3
• Low baseline electrolytes (potassium, phosphate, or magnesium) before feeding 2, 3

Nutritional Reintroduction Strategy

For severely malnourished patients (<70% ideal body weight):

• Start at 5-10 kcal/kg/day 1, 2, 3, 5
• Increase gradually by 5 kcal/kg every 24 hours over 4-7 days until reaching full requirements (25-30 kcal/kg/day) 3, 6
• Use macronutrient distribution of 40-60% carbohydrate, 30-40% fat, and 15-20% protein 2, 3
• Maintain protein intake at least 1.2-2.0 g/kg ideal body weight 3

For mildly to moderately malnourished patients:

• Higher calorie refeeding (≥1400 kcal/day or 10-20 kcal/kg/day) can be safely administered under close medical monitoring 3, 7
• Evidence supports that lower calorie refeeding is too conservative in this population 7

Route of administration:

• Enteral feeding (oral or nasogastric) is preferred over parenteral nutrition if intestinal function is preserved 4, 3
• Parenteral nutrition is not recommended and should only be used when enteral feeding cannot be tolerated 4

Aggressive Electrolyte Replacement Protocol

Phosphate supplementation:

• Administer 0.3-0.6 mmol/kg/day IV 1, 2, 3
• Maintain serum phosphate levels above 3.0 mg/dL 5
• Critical pitfall: Pay attention to rapid drops in phosphate levels rather than absolute values alone—hypophosphatemia can develop even when starting levels appear adequate 8

Potassium supplementation:

• Provide 2-4 mmol/kg/day 1, 2, 3
• Hypokalemia typically accompanies hypophosphatemia 3

Magnesium supplementation:

• Give 0.2 mmol/kg/day IV or 0.4 mmol/kg/day orally 1, 2, 3
• Hypomagnesemia commonly coexists with other electrolyte abnormalities 3

Calcium supplementation:

• Supplement as needed based on laboratory values 3

Monitoring Protocol

First 72 hours (critical period):

• Monitor electrolytes (phosphate, potassium, magnesium, calcium) daily 1, 2, 3
• In patients with detected hypophosphatemia, measure electrolytes 2-3 times daily 3
• Perform continuous cardiac monitoring or daily ECG to detect arrhythmias 1
• Monitor for clinical signs: edema, arrhythmias, confusion, respiratory failure, delirium 3, 5
• Strict glucose monitoring to avoid hyperglycemia 3
• Assess volume status, fluid balance, heart rate and rhythm 3

After 72 hours:

• Continue regular electrolyte monitoring until stable 1, 3
• Extend monitoring beyond 3 days if abnormalities persist 3

Cardiac complications are most likely within the first week, with delirium occurring later and more variably related to hypophosphatemia 5

Management of Complications

If hypophosphatemia develops during refeeding:

• Immediately increase phosphate supplementation to 0.3-0.6 mmol/kg/day IV 3
• Temporarily restrict energy supply to 5-10 kcal/kg/day for 48 hours 3
• Measure electrolytes 2-3 times daily 3
• Gradually resume caloric increase once phosphate stabilizes 3

If symptoms of refeeding syndrome develop:

• Temporarily decrease feeding to 5-10 kcal/kg/day rather than stopping completely to avoid rebound hypoglycemia 3
• Intensify electrolyte replacement 3
• Never stop feeding abruptly—taper gradually if necessary 4, 3

Critical Pitfalls to Avoid

Do not:

• Start feeding without prior thiamine administration 1, 3
• Use rapid, aggressive refeeding in severely malnourished patients (<70% ideal body weight) 1, 2
• Rely on normal baseline laboratory values to exclude risk—approximately 60% of anorexia nervosa patients show normal values despite severe malnutrition 1
• Correct electrolytes alone before feeding, as this provides false security without addressing massive intracellular deficits 3
• Stop thiamine prematurely—continue for the full minimum 3-day period even if symptoms improve 3
• Use parenteral nutrition unless intestinal failure occurs 4

Special Considerations

Severely malnourished patients (<70% ideal body weight):

• There is insufficient evidence to change the current conservative standard of care in this population 7
• Proceed with extreme caution, as cardiac arrest and delirium can occur within the first week of refeeding 5
• Up to one-third of deaths in anorexia nervosa are cardiac-related, with refeeding being a high-risk period 1, 2

Multidisciplinary approach:

• Coordinate care among gastroenterologists, psychiatrists, nutritionists, and medical teams 1
• Early involvement of nutrition support teams optimizes outcomes 3