What is the corrected sodium level in a patient with hyponatremia and hyperglycemia, with a sodium level of 131 mmol/L and a glucose level of 208 mg/dL?

Correcting Sodium in Hyperglycemia

The corrected sodium level for a patient with a measured sodium of 131 mmol/L and glucose of 208 mg/dL is approximately 133 mmol/L.

Formula and Calculation

• The standard formula for sodium correction in hyperglycemia is: increase in sodium by 1.6 mmol/L for every 5.6 mmol/L (100 mg/dL) increase in glucose above normal 1
• With a glucose of 208 mg/dL (approximately 108 mg/dL above normal):
  • Correction factor = (108 ÷ 100) × 1.6 = 1.73 mmol/L
  • Corrected sodium = 131 + 1.73 = 132.73 mmol/L (rounded to 133 mmol/L) 1

Clinical Significance

• This correction is necessary because hyperglycemia causes water to move from the intracellular to extracellular space, diluting the serum sodium 1
• The corrected value provides a more accurate assessment of the patient's true sodium status, which is important for clinical decision-making 2
• Even with correction, this patient's sodium remains in the low-normal range (133 mmol/L), which may still warrant clinical attention 3

Importance in Management

• Understanding the true sodium status helps prevent inappropriate treatment decisions 2
• Without correction, hyponatremia may be overestimated in hyperglycemic states, potentially leading to inappropriate sodium replacement 1
• The corrected sodium value should guide the tonicity of replacement solutions if needed 1

Special Considerations

• In patients with severe hyperglycemia or diabetic ketoacidosis (DKA), the corrected sodium may be in the hypernatremic range, requiring different management approaches 1
• In patients with renal insufficiency, the relationship between glucose and sodium may differ due to impaired osmotic diuresis 1, 4
• The corrected sodium may change during treatment of hyperglycemia due to ongoing fluid losses and should be monitored 1

Common Pitfalls

• Failing to correct sodium in hyperglycemic states can lead to inappropriate treatment decisions 2
• Over-aggressive correction of apparent hyponatremia in hyperglycemic patients can lead to hypernatremia once glucose normalizes 1
• Not considering the patient's volume status when interpreting sodium levels can lead to inappropriate management 2