The Cardiovascular
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Arterial blood gas (ABG) analyser

Identifies the primary acid–base disorder and checks compensation.

Arterial blood gas (ABG) analyser
Arterial pH
pH
PaCO2
mmHg
Bicarbonate (HCO3)
mmol/L
Sodium (optional, for anion gap)
mmol/L
Chloride (optional, for anion gap)
mmol/L
Complete the fields above to see the result.

When to use

  • Systematic interpretation of an arterial blood gas at the bedside.

Formula

Reference ranges: pH 7.35–7.45, PaCO2 35–45 mmHg, HCO3 22–26 mmol/L. Winter's expected PaCO2 = 1.5×HCO3 + 8 ± 2. Anion gap = Na − Cl − HCO3.

Pearls and pitfalls

  • An anion gap above the reference range points to an added high-gap metabolic acidosis even when pH looks compensated.

References

  1. Narins RG, Emmett M. Medicine (Baltimore). 1980;59(3):161-87.