What is corrected sodium used for?

Corrected Sodium: Purpose and Clinical Applications

Corrected serum sodium is primarily used to guide fluid therapy decisions in hyperglycemic crises by estimating the true sodium status when hyperglycemia artificially lowers measured sodium values. 1

What is Corrected Sodium?

• Corrected sodium is a calculated value that adjusts the measured serum sodium concentration to account for the dilutional effect of hyperglycemia 2
• The formula adds 1.6 mEq/L to the measured sodium value for each 100 mg/dL that glucose exceeds 100 mg/dL 1, 2
• This calculation provides a more accurate assessment of the patient's true sodium status when hyperglycemia is present 2, 3

Clinical Applications

Guiding Fluid Therapy in Hyperglycemic Crises

• In diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS), corrected sodium determines the appropriate fluid choice:
  • If corrected sodium is normal or elevated: Use 0.45% NaCl at 4-14 ml/kg/h 1
  • If corrected sodium is low: Use 0.9% NaCl at a similar rate 1

Monitoring for Cerebral Edema Risk

• Corrected sodium trajectory helps predict risk of cerebral edema in DKA patients 4
• A falling corrected sodium during treatment may signal developing cerebral edema, particularly in pediatric patients 4
• Maintaining appropriate changes in serum osmolality (not exceeding 3 mOsm/kg/h) helps prevent cerebral edema 1

Assessing Dehydration Severity

• Corrected sodium helps estimate the degree of hypertonicity due to osmotic diuresis in hyperglycemic crises 2
• In HHS, corrected sodium is often in the hypernatremic range (mean 160.8 mmol/L), indicating severe dehydration 2
• In DKA, corrected sodium is typically eunatremic (mean 141.1 mmol/L) but can vary significantly 2

Clinical Significance

• Corrected sodium is a better predictor of clinical outcomes than measured sodium in patients with extreme hyperglycemia 3
• Patients with corrected hyponatremia have higher 90-day mortality (adjusted HR 3.56) compared to those with normal corrected sodium 3
• Patients with severe corrected hypernatremia also show increased mortality (adjusted HR 2.68) 3
• Dysnatremia (abnormal sodium levels) is associated with longer hospital stays and increased 30-day mortality in hospitalized patients 5

Practical Application Algorithm

1. Calculate corrected sodium when glucose >100 mg/dL using formula:

   • Corrected [Na+] = Measured [Na+] + 1.6 × ([Glucose in mg/dL - 100]/100) 1

2. Use corrected sodium to guide fluid therapy:

   • Normal/high corrected sodium → 0.45% NaCl
   • Low corrected sodium → 0.9% NaCl 1

3. Monitor corrected sodium during treatment:

   • Recalculate as glucose levels change
   • Watch for falling corrected sodium (risk of cerebral edema) 4
   • Ensure serum osmolality changes do not exceed 3 mOsm/kg/h 1

Common Pitfalls

• Relying solely on measured sodium in hyperglycemic patients can lead to inappropriate fluid therapy 2, 3
• Failing to monitor corrected sodium during treatment may miss developing cerebral edema 4
• The corrected sodium formula may be less accurate in extreme hyperglycemia or profound hypervolemia 2
• Corrected sodium may change during treatment due to ongoing fluid losses and should be regularly recalculated 2