Medical Problems: Hyponatremia

OVERVIEW

This page is designed to organize content that is relevant to the topic of hyponatremia. This term is used often in medicine, and it is important that we become as familiar as possible with it.

Low sodium within the serum is defined as hyponatremia (source)
Low sodium within the serum is defined as hyponatremia (source)
WHAT EXACTLY IS IT?

Before going any farther, let us make sure we clearly define the “medical problem”. Hyponatremia refers to low levels of sodium within the serum. It is defined by sodium levels that are <135 mmol/L (although reference ranges may vary depending upon the lab doing the assay).

WHY IS IT A PROBLEM?

Sodium is an important electrolyte for the function of many different cells and tissues within the body. It is for this reason that a specific concentration of sodium is maintained within the serum. In the setting of hyponatremia, water will be osmotically driven into the brain cells in order to maintain this serum concentration. This in turn will result in cerebral edema and increased intracranial pressure. This can be dangerous (leading to deadly processes such as brain herniation) and also will cause the neurological symptoms elaborated more below.

It is important to appreciate the delicate balance between electrolytes and fluid that exist in the brain. Hyponatremia will cause influx of water into the brain. Similarly, rapid correction of hyponatremia will result in rapid water loss, as osmotic demyelination (source)
It is important to appreciate the delicate balance between electrolytes and fluid that exist in the brain. Hyponatremia will cause influx of water into the brain. Similarly, rapid correction of hyponatremia will result in rapid water loss, as osmotic demyelination (source)
ORGANIZING THE DIFFERENTIAL

The differential diagnosis for hyponatremia can be organized in a few different ways:

  • Can’t miss diagnosis
  • Organ systen
  • Disease category
  • Diagnostic modality
  • Most common diagnosis
CLINICAL “WORKUP”

Now that the possible causes of hyponatremia have been established, the focus can shift to how one would actually “work-up” a patient who presents with hyponatremia. 

  • Collecting the history
  • Performing the physical
  • Ordering studies/tests
  • Intrepreting clinical data
TREATMENT

The treatment of hyponatremia may vary depending on the etiology of the condition, and is elaborated upon more below:

 

Page Updated: 01.28.2017