A 19-year-old college student is brought to the emergency department by his roommates. They report that he ingested a large amount of a sweet-tasting, brightly colored liquid he found in a garage, believing it was a sports drink. On presentation, he is disoriented and slurring his words. His blood pressure is 120/75 mm Hg and his pulse is 100/min.
Laboratory studies:
- Serum sodium: 142 mEq/L
- Serum chloride: 105 mEq/L
- Serum bicarbonate: 14 mEq/L
- Blood urea nitrogen: 14 mg/dL
- Blood glucose: 90 mg/dL
- Measured serum osmolality: 345 mOsm/kg
What is this patient's serum osmolar gap in mOsm/kg ?
Cevap: 51 mOsm/kg H2O
Cevap
51
The osmolar gap is used to detect the presence of unmeasured, osmotically active substances in the blood, such as toxic alcohols (e.g., ethylene glycol, methanol). It is determined by subtracting the calculated serum osmolality from the measured serum osmolality. The formula for calculated osmolality is . For this patient, the calculated osmolality is mOsm/kg . Subtracting this from the measured osmolality of 345 mOsm/kg yields an osmolar gap of 51 mOsm/kg . A normal gap is typically less than 10; an elevated gap in this context strongly suggests ethylene glycol toxicity.
Adım Adım Çözüm
Anahtar Kavram
Serum Osmolar Gap Calculation
Alternatif Yöntem
In systems using SI units (mmol/L) rather than traditional US units, the formula for calculated osmolality does not require division by 18 or 2.8 and is instead: .
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