fluidosmolalitet

Fluidosmolalitet refers to the concentration of solute particles in a fluid, typically blood plasma or urine. It is a measure of how many osmoles (total number of solute particles) are dissolved in a given volume of solvent, usually expressed in milliosmoles per kilogram of water (mOsm/kg). Osmolality is a colligative property, meaning it depends on the number of solute particles rather than their identity.

In the context of bodily fluids, osmolality plays a crucial role in maintaining water balance. The body's cells regulate their water content by adjusting the osmolality of the extracellular fluid. For example, when the body is dehydrated, the osmolality of the blood increases, signaling the brain to release antidiuretic hormone (ADH). ADH then acts on the kidneys to increase water reabsorption, reducing water loss and diluting the blood. Conversely, when the body has excess water, blood osmolality decreases, leading to less ADH release and increased water excretion by the kidneys.

Normal plasma osmolality is typically between 275 and 295 mOsm/kg. Urine osmolality can vary much more widely, ranging from about 50 to 1200 mOsm/kg, depending on the body's hydration status and the kidney's ability to concentrate or dilute urine. Measuring fluid osmolality can be important in diagnosing various medical conditions, including diabetes insipidus, dehydration, and kidney disease. It helps assess the body's water and electrolyte balance and the effectiveness of kidney function.