What is the recommended dose of sodium bicarbonate (NaHCO3) for treating metabolic acidosis?

Calculating Sodium Bicarbonate Dose in Metabolic Acidosis

For severe metabolic acidosis (pH <7.1), administer 1-2 mEq/kg IV (typically 50-100 mEq or 50-100 mL of 8.4% solution) given slowly over several minutes, with repeat dosing guided by arterial blood gas analysis targeting a pH of 7.2-7.3, not complete normalization. 1

Initial Dosing Algorithm

Standard Adult Dosing

• Administer an initial bolus of 1-2 mEq/kg IV (typically 50-100 mEq or 50-100 mL of 8.4% solution) for severe metabolic acidosis with pH <7.1 and base excess <-10 1, 2
• Give the dose slowly over several minutes to minimize complications from hypertonic solution 1, 2
• In cardiac arrest, a rapid dose of 44.6-100 mEq (one to two 50 mL vials) may be given initially, continued at 44.6-50 mEq every 5-10 minutes as indicated by arterial pH monitoring 1, 2

Pediatric Dosing

• Children require 1-2 mEq/kg IV administered slowly 1, 3
• Infants under 2 years must receive only 0.5 mEq/mL (4.2%) concentration, achieved by diluting 8.4% solution 1:1 with normal saline or sterile water 1
• Children ≥2 years may use 8.4% solution, though dilution is often performed for safety 1

Calculating Bicarbonate Deficit

Practical Formula for Bedside Calculation

• Use the formula: Bicarbonate deficit (mEq) = 0.5 × body weight (kg) × (desired HCO3⁻ - actual HCO3⁻) 4
• Target a desired bicarbonate of approximately 15-18 mEq/L initially, which typically achieves a pH around 7.30 4
• This formula is designed to elevate pH to approximately 7.30, not to complete normalization, reducing risk of overtitration 4

Alternative Dosing Approach

• For less urgent metabolic acidosis, administer 2-5 mEq/kg body weight over 4-8 hours depending on severity 1, 2
• This produces measurable improvement in acid-base status while allowing time for physiologic adjustment 1, 2

Critical Indications and Contraindications

When to Give Bicarbonate

• Severe metabolic acidosis with pH <7.1 AND base excess <-10 1
• Life-threatening hyperkalemia (as temporizing measure while definitive therapy initiated) 1
• Tricyclic antidepressant or sodium channel blocker overdose with QRS prolongation >120 ms 1
• Diabetic ketoacidosis ONLY if pH <6.9 1

When NOT to Give Bicarbonate

• Do not give bicarbonate for hypoperfusion-induced lactic acidemia when pH ≥7.15 1, 5
• Multiple blinded randomized trials show no difference in hemodynamic variables or vasopressor requirements compared to equimolar saline 1, 5
• Do not use for tissue hypoperfusion-related acidosis as routine therapy 1
• Diabetic ketoacidosis with pH ≥7.0 does not benefit from bicarbonate 1

Continuous Infusion Dosing

For Ongoing Alkalinization

• After initial bolus, continue with infusion of 150 mEq/L solution at 1-3 mL/kg/hour if ongoing alkalinization needed 1
• For sodium channel blocker toxicity, give bolus of 50-150 mEq followed by continuous infusion of 150 mEq/L solution at 1-3 mL/kg/hour 1

Specific DKA Protocol

• For pH <6.9: infuse 100 mmol sodium bicarbonate in 400 mL sterile water at 200 mL/hour 1
• For pH 6.9-7.0: infuse 50 mmol sodium bicarbonate in 200 mL sterile water at 200 mL/hour 1

Monitoring Requirements During Therapy

Essential Parameters to Track

• Measure arterial blood gases every 2-4 hours to assess pH, PaCO2, and bicarbonate response 1
• Monitor serum electrolytes every 2-4 hours, including sodium (target <150-155 mEq/L), potassium, and ionized calcium 1
• Target pH of 7.2-7.3, avoiding pH >7.50-7.55 1

Repeat Dosing Strategy

• Further bicarbonate administration depends on clinical response and repeat arterial blood gas analysis 1, 2
• Do not attempt full correction of low total CO2 content during first 24 hours, as this may cause unrecognized alkalosis due to delayed ventilatory readjustment 2
• Achievement of total CO2 content of about 20 mEq/L at end of first day typically associates with normal blood pH 2

Critical Safety Considerations

Adverse Effects to Monitor

• Sodium and fluid overload from hypertonic solution 1, 5
• Increased PCO2 requiring adequate ventilation to clear excess CO2 1, 5
• Decreased ionized calcium (0.95 to 0.87 mmol/L), affecting cardiac contractility 1, 5
• Hypokalemia from intracellular potassium shift requiring replacement 1
• Paradoxical intracellular acidosis if given without adequate ventilation 1

Administration Precautions

• Never mix sodium bicarbonate with calcium-containing solutions or vasoactive amines (causes precipitation or inactivation) 1
• Flush IV line with normal saline before and after bicarbonate administration 1
• Ensure effective ventilation is established before giving bicarbonate, as it produces CO2 that must be eliminated 1

Common Clinical Pitfalls

Errors to Avoid

• Giving bicarbonate for lactic acidosis with pH ≥7.15 provides no hemodynamic benefit and may cause harm 1, 5
• Attempting complete pH normalization in first 24 hours risks severe alkalosis 2
• Ignoring the underlying cause—bicarbonate buys time but does not treat the disease 1
• Using bicarbonate without ensuring adequate ventilation causes paradoxical worsening of intracellular acidosis 1
• Failing to monitor ionized calcium, especially with doses >50-100 mEq 1, 5

Special Population Considerations

• In vasopressor-dependent patients with metabolic acidosis, early bicarbonate may improve mean arterial pressure at 6 hours and potentially reduce ICU mortality 6
• Chronic kidney disease patients require oral sodium bicarbonate 2-4 g/day (25-50 mEq/day) to maintain serum bicarbonate ≥22 mmol/L 1, 7
• Newborns require only 4.2% concentration with maximum rate of 8 mEq/kg/day 1