From the Guidelines
The formula for calculating corrected sodium in hyperglycemia is to add 1.6 mEq to the sodium value for every 100 mg/dl of glucose above 100 mg/dl.
Corrected Sodium Calculation
- The calculation is based on the principle that hyperglycemia causes a decrease in measured serum sodium levels due to the dilutional effect of glucose in the blood.
- The correction factor of 1.6 mEq per 100 mg/dl of glucose is a widely accepted value, as seen in studies such as 1, 2, and 3.
- To calculate the corrected sodium level, the following formula can be used: Corrected Sodium = Measured Sodium + (1.6 mEq x (Glucose - 100) / 100).
- For example, if the measured sodium level is 130 mEq/L and the glucose level is 300 mg/dl, the corrected sodium level would be: Corrected Sodium = 130 + (1.6 x (300 - 100) / 100) = 130 + (1.6 x 2) = 130 + 3.2 = 133.2 mEq/L.
Clinical Application
- The corrected sodium level is an important consideration in the management of patients with hyperglycemic crises, such as diabetic ketoacidosis (DKA) and hyperglycemic hyperosmolar state (HHS) 4.
- Accurate calculation of corrected sodium levels can help guide fluid and electrolyte management, as well as insulin therapy, in these patients.
From the Research
Calculating Corrected Sodium in Hyperglycemia
The formula for calculating corrected sodium in hyperglycemia is based on the idea that for every 5.6 mmol/L decrease in glucose, the sodium level increases by 1.6 mmol/L 5. This formula provides a reasonable estimate of the degree of hypertonicity due to losses of hypotonic fluids through osmotic diuresis at presentation of diabetic ketoacidosis (DKA) or hyperglycemic hyperosmolar state (HHS).
Key Points to Consider
- The corrected sodium level is a better indicator of clinical outcomes compared to measured sodium levels, especially in patients with severe hyperglycemia 6.
- The combination of DKA, HHS, and hypernatremia is rare and extremely challenging to manage, but the most challenging part of this condition is selecting the correct type of fluids to treat these conditions 7.
- Hyperglycemic patients with hypernatremia have large deficits of body water and usually hypovolemia, and develop severe clinical manifestations and significant mortality 8.
- Currently available formulae to guide infusion therapy in hyper- and normonatraemic states do not accurately predict changes of serum sodium in the individual ICU patient 9.
Formula for Corrected Sodium
- Corrected [Na] = [Na] increase by 1.6 mmol/L per 5.6 mmol/L decrease in [Glu] [5]
- This formula can be used to estimate the degree of hypertonicity due to losses of hypotonic fluids through osmotic diuresis at presentation of DKA or HHS.