Expected PaCO₂ in Metabolic Acidosis (Winter's Formula)
Calculates expected respiratory compensation (PaCO₂) in metabolic acidosis using Winter's formula. Helps identify concurrent respiratory acid-base disorders.
Score interpretation
PaCO₂ within expected range — appropriate respiratory compensation for metabolic acidosis.
→ Pure metabolic acidosis. Identify and treat underlying cause (DKA, lactic acidosis, renal failure, toxic ingestion).
Measured PaCO₂ higher than expected — additional respiratory acidosis present.
→ Assess respiratory function. Consider ventilatory support. Treat primary cause of metabolic acidosis.
Measured PaCO₂ lower than expected — additional respiratory alkalosis present.
→ Identify cause of hyperventilation (pain, anxiety, sepsis, CNS disorder, salicylate toxicity).
Interpretation bands for the Winter's Formula. Apply clinical judgement and local guidance.
References
- Winter SD et al. The fall of serum bicarbonate levels in linear fashion with decreasing pCO2. Arch Intern Med. 1990;150(2):311-313.
- Narins RG, Emmett M. Simple and mixed acid-base disorders: a practical approach. Medicine. 1980;59(3):161-187.
Related
Curated clinical cross-links plus same-class fallbacks.
- Sodium Bicarbonate · Alkali Therapy (Metabolic Acidosis / CKD-Related Acidosis)
- Noradrenaline (Norepinephrine) · Vasopressor (Alpha-1 and Beta-1 Agonist)
- Tranexamic Acid (ICU/Trauma/Surgical) · Antifibrinolytic
- Doxapram hydrochloride · Respiratory stimulant
- Trimetazidine · Metabolic Anti-Anginal
- Acipimox · Lipid-modifying agent (Nicotinic acid derivative)
- Hyperkalaemia Management · UK Kidney Association Guidelines 2020; NICE CKD Guidelines
- Rhabdomyolysis · Renal Association 2018; UpToDate 2024
- Hypocalcaemia (Adult) · Society for Endocrinology
- SIADH (Endocrine Perspective) · European Hyponatraemia Guidelines 2014
- Hepatorenal Syndrome · EASL 2018; ICA 2015
- Acute Kidney Injury (AKI) · KDIGO 2012 / NICE AKI 2019
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.