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Nephrology

Winter's Formula (expected PaCO2 in metabolic acidosis)

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Formula

Expected PaCO2 (mmHg) = 1.5 x HCO3 (mmol/L) + 8, +/- 2.

Limitations

  • Valid for metabolic acidosis only, not for mixed or chronic respiratory disorders; it assumes that respiratory compensation has had time to develop.
  • The equation is taken from secondary sources (MSD Manual; Pan Afr Med J 2022); the abstract of the original 1967 paper does not state it.

References

  1. Quantitative displacement of acid-base equilibrium in metabolic acidosis. Albert MS, Dell RB, Winters RW. Quantitative displacement of acid-base equilibrium in metabolic acidosis. Ann Intern Med. 1967;66(2):312-322. PMID 6016545