1. What is Serum Osmolality?

Serum osmolality is a measure of the concentration of dissolved particles in blood serum. It's an important indicator of the body's water balance and helps evaluate electrolyte and acid-base disorders.

2. How Does the Calculator Work?

The calculator uses the serum osmolality equation:

Where:

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

Explanation: This equation estimates the osmotic concentration of serum based on its major osmotically active components.

3. Importance of Serum Osmolality Calculation

Details: Serum osmolality measurement is crucial for diagnosing and monitoring fluid and electrolyte imbalances, evaluating dehydration or overhydration, assessing renal function, and detecting toxic alcohol ingestions.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is the normal range for serum osmolality?
A: Normal serum osmolality ranges from 275 to 295 mOsm/kg. Values outside this range may indicate various medical conditions.

Q2: Why is the osmolar gap important?
A: The osmolar gap (measured osmolality minus calculated osmolality) helps detect the presence of unmeasured osmotically active substances, such as toxic alcohols.

Q3: When should serum osmolality be measured?
A: It should be measured when evaluating altered mental status, suspected dehydration, diabetes insipidus, or possible toxic alcohol ingestion.

Q4: Are there limitations to this calculation?
A: This formula provides an estimate and may not account for all osmotically active substances. Measured osmolality may differ in certain conditions.

Q5: How does this relate to fluid therapy?
A: Serum osmolality helps guide appropriate fluid replacement therapy, especially in cases of hypernatremia or hyponatremia.