Sodium Correction for Hyperglycemia

Sodium Correction for Hyperglycemia (Katz / Hillier)
mEq/L
mg/dL
Calculates the actual sodium level in patients with hyperglycemia.

Why Use

Some experts use the severity of corrected hyponatremia as a predictor of clinical outcome. Hyperglycemia causes osmotic shifts of water from the intracellular to the extracellular space, causing a relative dilutional hyponatremia.

When to Use

Use in patients with elevated serum glucose who are also found to have a low serum sodium level on lab work.

Formula

Corrected Sodium (Katz, 1973) = Measured sodium + 0.016 * (Serum glucose - 100) Corrected Sodium (Hillier, 1999) = Measured sodium + 0.024 * (Serum glucose - 100) Note: Serum glucose must be in mg/dL for these formulae to work.

Pearls / Pitfalls

The classic correction factor of 1.6 mEq/L in serum sodium for every 100 mg/dL increase in serum glucose was challenged by a paper by Hillier et al. in 1999; sometimes their factor of 2.4 mEq/L is used. Repeat sodium levels regularly, as sodium will shift with ongoing fluid replacement. On initial laboratory tests, check osmolality to ensure there is no osmolality gap, as this can lead to false hyponatremia ( pseudohyponatremia ). In extremely hyperglycemic patients, the corrected hyponatremia may reveal true hyponatremia, which can lead to worse outcomes. Therefore, ensure regular lab monitoring during fluid replacement and glucose control.

Advice

Act on the corrected sodium level, not the measured sodium level. Treat the underlying cause of hyperglycemia. Regularly obtain repeat lab work (frequency will depend on clinical condition and severity of abnormalities) to monitor changes.

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