When is bicarbonate (bicarb) indicated in shock?

Bicarbonate Therapy in Shock

Sodium bicarbonate therapy is generally not recommended for shock patients with hypoperfusion-induced lactic acidemia unless pH falls below 7.15, and even then should be used cautiously with close monitoring of hemodynamics and electrolytes. 1

When Bicarbonate Is NOT Indicated in Shock

• pH ≥ 7.15: Strong evidence recommends against bicarbonate therapy for hypoperfusion-induced lactic acidemia with pH ≥ 7.15 1
• Routine shock management: Bicarbonate should not be used routinely to improve hemodynamics or reduce vasopressor requirements 1
• Primary goal: Treatment should focus on correcting the underlying cause of shock rather than the acidosis itself 2

When Bicarbonate MAY Be Considered in Shock

Bicarbonate therapy may be considered in the following specific scenarios:

1. Severe acidosis: When pH falls below 7.15 (and particularly below 7.0) 1, 3, 4
2. Specific types of shock:
   • Cardiac arrest due to sodium channel blocker toxicity (first-line therapy) 3, 2
   • Circulatory insufficiency due to severe dehydration 2
   • Severe primary lactic acidosis 2

Dosing and Administration When Indicated

If bicarbonate is deemed necessary (pH < 7.15):

• Initial dose: 1-2 mEq/kg IV 3, 2
• In cardiac arrest: 44.6-100 mEq (1-2 vials of 50 mL) initially, then 44.6-50 mEq every 5-10 minutes as needed 2
• In less urgent forms: 2-5 mEq/kg over 4-8 hours, depending on acidosis severity 2
• Administration approach: Stepwise, with target total CO2 content of about 20 mEq/L at the end of the first day 3, 2

Monitoring During Bicarbonate Administration

When bicarbonate is administered, close monitoring is essential:

• Arterial blood gases
• Serum electrolytes (especially potassium, calcium, and sodium)
• ECG
• Blood pressure
• Mental status 3

Potential Complications and Pitfalls

Bicarbonate administration can cause several adverse effects:

• CO2 generation: Bicarbonate generates CO2 which must be eliminated through ventilation; inadequate ventilation may worsen acidosis 3, 5
• Electrolyte disturbances:
  • Hypernatremia (avoid serum sodium > 150-155 mEq/L) 3
  • Decreased ionized calcium (by approximately 10%) 4
• Hemodynamic effects: May cause transient decreases in cardiac output and mean arterial pressure 5
• Fluid overload: Bicarbonate solutions are hypertonic 2
• Paradoxical intracellular acidosis: Can occur despite systemic alkalinization 5

Alternative Approaches

1. THAM (tromethamine): May be considered as an alternative, especially in patients with hypernatremia or mixed acidosis with high PaCO2 3
2. Bicarbonated Ringer's solution: Some evidence suggests it may be more effective than lactated Ringer's solution in hemorrhagic shock, with better correction of acidosis and reduced inflammatory markers 6, 7
3. Continuous renal replacement therapy: When used during severe acidosis, bicarbonate-based replacement fluid is recommended over citrate 4

Clinical Decision Algorithm

1. Assess pH level:

   • pH ≥ 7.15: Do not administer bicarbonate 1
   • pH < 7.15: Consider bicarbonate based on clinical context 1, 3
   • pH < 7.0: Stronger consideration for bicarbonate therapy 3, 4

2. Evaluate specific shock etiology:

   • Sodium channel blocker toxicity: Use bicarbonate as first-line therapy 3
   • Other shock types: Focus on treating underlying cause first 2, 4

3. If bicarbonate is administered:

   • Ensure adequate ventilation to clear CO2 3, 4
   • Monitor electrolytes, especially calcium 4
   • Use slow infusion rather than rapid bolus when possible 4
   • Target modest correction (total CO2 ~20 mEq/L) in first 24 hours 2

Remember that the most effective therapy for lactic acidosis due to shock is reversing the underlying cause of shock, not bicarbonate administration 4.