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Winters’ formula for metabolic acidosis

Expected respiratory compensation (PaCO₂) in metabolic acidosis.

Winters’ formula for metabolic acidosis
Bicarbonate (HCO₃⁻)
mEq/L
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When to use

  • Checking whether respiratory compensation for a metabolic acidosis is adequate, and detecting a superimposed respiratory disorder.

Formula

Expected PaCO₂ = 1.5 × [HCO₃⁻] + 8 ± 2 mmHg.

Pearls and pitfalls

  • A quick bedside check: PaCO₂ should approximate the last two digits of the arterial pH when compensation is appropriate.

References

  1. Albert MS, Dell RB, Winters RW. Quantitative displacement of acid-base equilibrium in metabolic acidosis. Ann Intern Med. 1967;66(2):312–22.