A 45-year-old male is evaluated in the emergency department for altered mental status. His spouse found him acting confused and stumbling in their basement next to several open containers of antifreeze. Vital signs are temperature (), blood pressure mm Hg, pulse /min, and respirations /min. He appears intoxicated but has no scent of alcohol on his breath. Laboratory results are as follows:
| Test | Result |
|---|---|
| Sodium | mEq/L |
| Potassium | mEq/L |
| Chloride | mEq/L |
| Bicarbonate | mEq/L |
| Blood urea nitrogen | mg/dL |
| Creatinine | mg/dL |
| Glucose | mg/dL |
| Measured serum osmolality | mOsm/kg |
| Blood ethanol level | Undetectable |
Based on these findings, what is the patient's serum osmolar gap?
Answer: 31 mOsm/kg H2O
Answer
31
The patient has a toxic alcohol ingestion (likely ethylene glycol from antifreeze), presenting with a high anion gap metabolic acidosis and an elevated osmolar gap. The osmolar gap is calculated as the difference between the measured serum osmolality and the calculated serum osmolality. With a calculated osmolality of 287 mOsm/kg H2O and a measured osmolality of 318 mOsm/kg H2O, the resulting gap is 31.
Step-by-Step Solution
Key Concept
Calculation of the serum osmolar gap to identify the presence of unmeasured osmotically active substances, such as toxic alcohols.