1. What is Serum Osmolality?

Serum osmolality measures the concentration of dissolved particles in blood. It's important for assessing fluid and electrolyte balance, and for detecting conditions like dehydration, diabetes insipidus, or toxin ingestion.

2. How Does the Calculator Work?

The calculator uses the serum osmolality equation:

Where:

• \( Na \) — Sodium concentration (mEq/L)
• \( Glucose \) — Blood glucose level (mg/dL)
• \( BUN \) — Blood urea nitrogen level (mg/dL)

Explanation: The equation accounts for the major osmotically active particles in blood: sodium (and its accompanying anions), glucose, and urea.

3. Importance of Osmolality Calculation

Details: Serum osmolality is crucial for evaluating water balance disorders, assessing the severity of hyperglycemia, and detecting osmolar gaps that might indicate the presence of toxins like ethanol or methanol.

4. Using the Calculator

Tips: Enter sodium in mEq/L, glucose and BUN in mg/dL. All values must be valid (sodium > 0, glucose and BUN ≥ 0).

5. Frequently Asked Questions (FAQ)

Q1: What is a normal serum osmolality range?
A: Normal range is typically 275-295 mOsm/kg. Values outside this range may indicate fluid or electrolyte disorders.

Q2: What is the osmolar gap?
A: The difference between measured and calculated osmolality. A gap >10 suggests unmeasured osmoles like alcohols or toxins.

Q3: Why is sodium multiplied by 2?
A: Sodium is accompanied by anions (mainly chloride) that contribute equally to osmolality, hence the doubling.

Q4: When is this calculation most useful?
A: In evaluating hyponatremia, hyperglycemic states, suspected alcohol intoxication, and monitoring treatment of these conditions.

Q5: Does this account for all osmotically active particles?
A: No, it's an estimate. Other particles like potassium, calcium, and magnesium contribute minimally to normal osmolality.