ICU Map

Winter's Formula

Predicted respiratory compensation (expected PaCO2) for a primary metabolic acidosis.

Formula

Expected PaCO2 = 1.5 × HCO3 + 8 (± 2)

Result

Enter all values to see the result.

Limitations

  • Only valid for a primary metabolic acidosis — it does not predict expected compensation for any other primary acid-base disorder.
  • Assumes the respiratory system is able to compensate; a patient with respiratory failure or heavy sedation may not reach the predicted PaCO2 even without a second acid-base process.
  • The ± 2 mmHg margin around the predicted value should be applied — this calculator shows only the midpoint, not the full expected range.

References

  • Narins RG, Emmett M. Simple and mixed acid-base disorders: a practical approach. Medicine (Baltimore). 1980 (describes Winter's formula and related compensation relationships).

Clinical Context & Relevant Topics (3)

Disease Reference
Acid-Base Disorders: Comprehensive Critical Care Approach

Stepwise 6-step interpretation algorithm, compensation formulas, albumin-corrected anion gap, delta ratio, and Stewart physicochemical (SID) principles.

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Metabolic Acidosis: HAGMA, NAGMA, & Bicarbonate Evidence

Differential diagnosis (GOLD MARK vs HARDCARP), toxic alcohol osmolar gaps, Urine Anion Gap, and current sodium bicarbonate evidence including BICAR-ICU and BICARICU-2.

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Diabetic Ketoacidosis (DKA)

Pathophysiology, SGLT2i euglycemic DKA, balanced fluid resuscitation, potassium-before-insulin safety rules, dextrose addition kinetics, and subcutaneous transition.

Open Topic →

Relevant Clinical Pathways (6)

Decision Protocols
Renal Replacement Therapy & CRRT Initiation

From urgent 'AEIOU' indication screening and modality selection to vascular access, dosing, and anticoagulation.

Launch Pathway →
Acute Severe Metabolic Acidosis Evaluation

From primary disorder confirmation and Anion Gap calculation to Winter's compensation, delta ratio, and targeted source control.

Launch Pathway →