Calculadora de Osmolaridade

The Osmolality Calculator estimates plasma osmolality from serum sodium, glucose, and urea levels. The formula used is Osm = 2·Na + glucose/18 + urea/6, with the result expressed in mosm/kg. This estimation is useful for assessing fluid and electrolyte balance in patients.

The calculation involves three steps: first, multiply sodium by 2 to account for accompanying anions. Then, divide glucose by 18 to convert from mg/dL to mmol/L. Finally, divide urea by 6 to obtain the urea contribution in mmol/L. The sum of these three components provides the estimated osmolality.

This calculator is commonly used in clinical settings, such as evaluating electrolyte disturbances, monitoring patients with decompensated diabetes, renal failure, or after surgeries. It also helps differentiate between hypotonic and isotonic hyponatremia, and in suspicion of alcohol intoxication (e.g., ethanol or methanol).

Important caveats: the formula provides an estimate and does not replace directly measured osmolality. In hyperlipidemia or hyperproteinemia, sodium may be falsely low (pseudonatremia). Additionally, the presence of alcohols or other unmeasured solutes can cause a significant osmolar gap, requiring further investigation.