Episode 967: Dilutional Hyponatremia

Contributor: Taylor Lynch, MD

Educational Pearls:

Dilutional Hyponatremia:

• Occurs when there is an excess of free water relative to sodium in the body.
• Causes a falsely low sodium concentration without a true change in total body sodium.

Commonly seen in DKA:

• Hyperglycemia raises plasma osmolality.
• Water shifts from the intracellular to extracellular space.
• This dilutes serum sodium, creating apparent hyponatremia.

Corrected sodium calculation:

Use tools like MDCALC, or apply this formula:

• Add 1.6 mEq/L to the measured sodium for every 100 mg/dL increase in glucose above 100.

Clinical relevance:

• Considering corrected sodium in DKA is crucial, as the lab value may not be reflective of actual sodium depletion.
• True severe hyponatremia can lead to complications like seizures
  • May require treatment with hypertonic saline.

References:

1. Fulop M. Acid–base problems in diabetic ketoacidosis. Am J Med Sci. 2008;336(4):274-276. doi:10.1097/MAJ.0b013e318180f478
2. Palmer BF, Clegg DJ. Electrolyte and Acid–Base Disturbances in Patients with Diabetes Mellitus. N Engl J Med. 2015;373(6):548-559. doi:10.1056/NEJMra1503102
3. Spasovski G, Vanholder R, Allolio B, et al. Diagnosis and management of hyponatremia: a review. JAMA. 2014;312(24):2640–2650. doi:10.1001/jama.2014.13773

Summarized by Ashley Lyons, OMS3 | Edited by Ashley Lyons & Jorge Chalit, OMS4

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