Does refeeding syndrome cause hypernatremia?

Refeeding Syndrome Does Not Cause Hypernatremia

No, refeeding syndrome does not cause hypernatremia; it typically causes hypophosphatemia, hypokalemia, and hypomagnesemia. 1, 2

Electrolyte Abnormalities in Refeeding Syndrome

Refeeding syndrome is characterized by specific electrolyte disturbances that occur when nutrition is reintroduced after a period of malnutrition or starvation. The key electrolyte abnormalities include:

• Primary electrolyte disturbances:
  • Hypophosphatemia (most clinically significant)
  • Hypokalemia
  • Hypomagnesemia
  • Thiamine deficiency 1, 2, 3

These electrolyte shifts occur due to the rapid transition from a catabolic to an anabolic state when nutrition is reintroduced. The sudden increase in insulin secretion drives glucose, phosphate, potassium, and magnesium into cells, leading to decreased serum levels of these electrolytes 3.

Pathophysiology of Refeeding Syndrome

The mechanism of refeeding syndrome involves:

1. Reintroduction of carbohydrates after starvation causes insulin release
2. Insulin promotes cellular uptake of phosphate, potassium, and magnesium
3. Depleted total body stores cannot compensate for this intracellular shift
4. Resultant serum hypophosphatemia, hypokalemia, and hypomagnesemia 1, 3

Notably, sodium retention and fluid overload can occur in refeeding syndrome, but hypernatremia (elevated serum sodium) is not a characteristic feature 4, 1.

Risk Factors for Refeeding Syndrome

High-risk patients include those with:

• BMI <16 kg/m²
• Unintentional weight loss >15% in 3-6 months
• Little or no nutritional intake for >10 days
• Low baseline electrolyte levels (potassium, phosphate, magnesium)
• History of chronic alcoholism or anorexia nervosa 1, 5

Prevention and Management

To prevent refeeding syndrome:

1. Identify at-risk patients using the criteria above

2. Start nutrition cautiously:

   • Begin with 5-15 kcal/kg/day
   • Gradually increase over 5-10 days
   • Aim for full nutritional requirements by days 7-10 1

3. Provide prophylactic electrolyte supplementation:

   • Potassium: 2-4 mmol/kg/day
   • Phosphate: 0.3-0.6 mmol/kg/day
   • Magnesium: 0.2 mmol/kg/day IV or 0.4 mmol/kg/day orally 1

4. Administer thiamine before initiating nutrition:

   • 300 mg IV before starting nutrition
   • 200-300 mg IV daily for at least 3 more days 1

5. Monitor electrolytes closely:

   • Check phosphate, potassium, and magnesium during first 72 hours
   • Watch for signs of fluid overload and cardiac dysfunction 1

Clinical Pitfalls to Avoid

1. Don't confuse with other electrolyte disorders: Hypernatremia is typically caused by water loss or sodium gain, not by refeeding syndrome 4.

2. Don't overlook refeeding syndrome in kidney patients: Even patients with advanced kidney disease who typically have hyperphosphatemia, hypermagnesemia, and hyperkalemia can develop refeeding syndrome with paradoxical hypophosphatemia 6.

3. Don't miss the diagnosis: Refeeding syndrome is often underdiagnosed due to lack of awareness and non-specific clinical presentation 3, 7.

4. Don't rush nutrition: Aggressive refeeding can precipitate severe electrolyte shifts and potentially fatal complications 1, 5.

In summary, while refeeding syndrome causes several serious electrolyte disturbances, hypernatremia is not among them. The hallmark electrolyte abnormalities are hypophosphatemia, hypokalemia, and hypomagnesemia.