Bicarbonate Replacement
Calculates NaHCO₃ deficit and replacement dose for metabolic acidosis.
Calculator
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Why use it
Quantifies NaHCO₃ needs and prevents over- or under-replacement. Rapid estimation tool for emergency and ICU settings.
About
Calculates the bicarbonate deficit and sodium bicarbonate replacement dose for patients with metabolic acidosis. Uses the standard formula: Deficit = 0.4 × weight × (target HCO₃ - measured HCO₃).
When to use
- Symptomatic metabolic acidosis (pH <7.2 or HCO₃ <15 mEq/L)
- Severe hyperchloremic acidosis (e.g., diarrhea, RTA, post-resuscitation)
- DKA with bicarbonate supplementation consideration (pH <6.9)
- Planning NaHCO₃ infusion rate and volume
Formula
HCO₃ deficit (mEq) = 0.4 × weight (kg) × [target HCO₃ - measured HCO₃]
Volume of 8.4% NaHCO₃ (mL) = deficit mEq (since 8.4% = 1 mEq/mL)
Volume of 4.2% NaHCO₃ (mL) = deficit × 2 (since 4.2% = 0.5 mEq/mL)
Number of 50 mEq ampules = deficit / 50
Pearls & pitfalls
- NaHCO₃ is controversial in most causes of metabolic acidosis — evidence best for hyperchloremic acidosis.
- Generally avoid if pH >7.2 in lactic acidosis (may worsen intracellular acidosis).
- Each 50 mEq ampule also delivers 50 mEq of Na⁺ — watch for hypernatremia.
- Target HCO₃ typically 15-18 mEq/L (partial correction), NOT full normalization.
- Treat underlying cause simultaneously.
- Hypocalcemia and hypokalemia may worsen after bicarbonate administration.
Next steps
Replace 50% of deficit over first 2-4 hours; reassess ABG. Each 50 mEq NaHCO₃ ampoule = 50 mEq in ~50 mL. Mix in D5W (not NS) to avoid hyperchloremia. Monitor Na⁺, K⁺, and pH closely.
Evidence
Based on standard physiology: bicarbonate space ≈ 40-50% of body weight for severe acidosis. Cooper et al. Crit Care Med 2000.