How this calculator works
This educational calculation uses the fixed 0.5 L/kg approximation described in the cited clinical pharmacy teaching guideline. Bicarbonate distribution changes with acid-base status, so this is an estimate of an amount, not a dose or infusion instruction. It does not decide whether bicarbonate treatment is indicated. The result is an estimate for information only and is not medical advice.
Formula
Estimated deficit (mmol) = 0.5 L/kg × weight (kg) × (desired - actual bicarbonate in mmol/L). One mmol of bicarbonate is one mEq.
Worked example
At 70 kg, raising the modelled bicarbonate from 12 to 18 mmol/L gives 0.5 × 70 × 6 = 210 mmol. At 60 kg with a 4 mmol/L difference, the estimate is 120 mmol.
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Frequently asked questions
Why use 0.5?
It is one published distribution approximation. Other models use different volumes; they are not interchangeable prescriptions.
Does the result give a sodium bicarbonate volume?
No. Solution strengths, sodium load, ventilation and the underlying cause need clinical assessment.
What happens when desired and actual match?
The estimated deficit is zero. Weight cannot be recovered from a zero concentration difference.