What is the role and dosing of intravenous (IV) sodium bicarbonate in treating severe metabolic acidosis?

Role and Dosing of IV Sodium Bicarbonate in Severe Metabolic Acidosis

IV sodium bicarbonate should be reserved for severe metabolic acidosis with pH ≤ 7.15, with an initial dose of 1-2 mEq/kg administered over 30-60 minutes, and should not be used routinely for acidosis due to tissue hypoperfusion. 1, 2

Indications for IV Sodium Bicarbonate

IV sodium bicarbonate is indicated in the following conditions:

• Severe metabolic acidosis (pH ≤ 7.15) 1, 3
• Metabolic acidosis in severe renal disease 2
• Circulatory insufficiency due to shock or severe dehydration 2
• Cardiac arrest due to sodium channel blocker toxicity 1
• Drug intoxications (barbiturates, salicylates, methyl alcohol) 2
• Hemolytic reactions requiring urine alkalinization 2
• Severe diarrhea with significant bicarbonate loss 2

Contraindications and Situations to Avoid Use

• Do not use sodium bicarbonate to treat metabolic acidosis arising from tissue hypoperfusion (lactic acidosis) unless pH falls below 7.15 4, 1
• Avoid in patients with mixed acidosis with high PaCO₂ levels (THAM may be preferred) 5
• Not recommended for routine use in diabetic ketoacidosis 6
• Not indicated for rhabdomyolysis (no improvement in patient-centered outcomes) 6

Dosing Guidelines

1. Initial dosing:

   • 1-2 mEq/kg IV as initial bolus 1, 3
   • Administer over 30-60 minutes 1

2. For severe acidosis (pH < 7.0):

   • Consider 2-5 mEq/kg over 4-8 hours 1
   • Target total CO₂ content of approximately 20 mEq/L at the end of the first day 1

3. For cardiac arrest:

   • 44.6-100 mEq initially, then 44.6-50 mEq every 5-10 minutes as needed 1

4. Administration method:

   • Volume of each infusion should be within 125-250 mL given over 30 minutes 7
   • Maximum of 1000 mL within 24 hours after initiation 7

Monitoring During Administration

• Arterial blood gases
• Serum electrolytes (especially potassium, calcium, and sodium)
• ECG
• Blood pressure
• Mental status 1

Special Considerations

• Acute Kidney Injury: Recent evidence suggests patients with severe acidosis and acute kidney injury may benefit from sodium bicarbonate therapy 7, 8
• Hypernatremia: THAM may be preferred over sodium bicarbonate in patients with hypernatremia as sodium bicarbonate increases serum sodium while THAM may decrease it 5
• Hyperkalemia: Sodium bicarbonate is preferred over THAM in patients with hyperkalemia as it decreases serum potassium 5
• Duration of Effect: The alkalinizing effect of sodium bicarbonate typically lasts longer (4+ hours) compared to THAM (3 hours) 5

Potential Adverse Effects

• Metabolic alkalosis
• Hypernatremia
• Hypocalcemia 7
• Volume overload
• Paradoxical intracellular acidosis
• Decreased cardiac output
• Increased PaCO₂ 5

Clinical Decision Algorithm

1. Assess severity of acidosis:

   • If pH > 7.15: Focus on treating underlying cause without bicarbonate
   • If pH ≤ 7.15: Consider bicarbonate therapy while addressing underlying cause

2. Evaluate etiology:

   • If due to tissue hypoperfusion: Avoid bicarbonate unless pH < 7.15
   • If due to renal failure, drug intoxications, or severe bicarbonate losses: Consider bicarbonate therapy

3. Check for special circumstances:

   • If hypernatremia present: Consider THAM instead
   • If hyperkalemia present: Sodium bicarbonate preferred
   • If acute kidney injury present: Lower threshold for bicarbonate use

4. Administer appropriate dose:

   • Start with 1-2 mEq/kg over 30-60 minutes
   • Reassess pH and clinical status
   • Adjust subsequent dosing based on response