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Plasma Osmolality Formula:
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Plasma Osmolality is a measure of plasma particles present in the fluid medium. The osmolality of plasma is typically in the range of 285-295 milliosmoles/kg and is an important indicator of the body's water-electrolyte balance.
The calculator uses the Plasma Osmolality formula:
Where:
Explanation: This formula provides a simplified calculation of plasma osmolality based on sodium concentration, which is the primary determinant of plasma osmotic pressure.
Details: Plasma osmolality measurement is crucial for assessing fluid and electrolyte balance, diagnosing dehydration or overhydration, and monitoring patients with renal disorders or diabetes insipidus.
Tips: Enter sodium concentration in mOsm/kg. The value must be valid (greater than 0). The calculator will compute the plasma osmolality using the standard formula.
Q1: What is the normal range for plasma osmolality?
A: Normal plasma osmolality ranges from 285-295 mOsm/kg in healthy individuals.
Q2: Why is sodium concentration used to calculate osmolality?
A: Sodium is the primary extracellular cation and the main determinant of plasma osmotic pressure, making it a reliable indicator for osmolality calculation.
Q3: When should plasma osmolality be measured?
A: It should be measured when assessing fluid balance disorders, evaluating patients with altered mental status, or monitoring treatment for dehydration or electrolyte imbalances.
Q4: Are there limitations to this calculation method?
A: This simplified formula provides an estimate. For precise measurement, direct osmolality measurement using freezing point depression is recommended, especially when other osmotically active substances are present.
Q5: How does plasma osmolality relate to clinical conditions?
A: Elevated osmolality may indicate dehydration, hypernatremia, or diabetes mellitus, while decreased osmolality may suggest overhydration, hyponatremia, or syndrome of inappropriate antidiuretic hormone secretion (SIADH).