plasmaalsmolalitet

Plasmaosmolaritet is a measure of the concentration of dissolved particles in the blood plasma. It is primarily determined by the levels of sodium, chloride, and bicarbonate, along with small amounts of other solutes like glucose and urea. Osmolaritet is expressed in milliosmoles per liter (mOsm/L). A normal range for plasma osmolaritet in adults is typically between 275 and 295 mOsm/L. This value is crucial for maintaining the balance of water between the blood plasma and the body's cells.

Changes in plasma osmolaritet can indicate various physiological conditions. An elevated plasma osmolaritet, known as hyperosmolarity, can result from dehydration, uncontrolled diabetes mellitus (leading to hyperglycemia), or certain types of kidney disease. Conversely, a decreased plasma osmolaritet, or hypoosmolarity, can be caused by overhydration, conditions affecting sodium levels like SIADH (Syndrome of Inappropriate Antidiuretic Hormone secretion), or severe liver disease.

The body tightly regulates plasma osmolaritet through hormonal mechanisms, primarily involving antidiuretic hormone (ADH) and the thirst mechanism. ADH acts on the kidneys to increase water reabsorption when osmolaritet is high, thus diluting the plasma. When osmolaritet is low, ADH secretion is suppressed, leading to increased water excretion. Monitoring plasma osmolaritet is an important diagnostic tool in clinical medicine for assessing hydration status and identifying metabolic disturbances.