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Bicarb: Not Always the Quick Fix

Acidosis is a critical condition in which there is an excess of acid in the body fluids, causing a decrease in blood pH (normally 7.35–7.45). This can lead to significant physiological disturbances and requires careful diagnosis and management. Broadly, acidosis is classified into two main types: metabolic and respiratory.

Types of Acidosis

  1. Metabolic Acidosis
    • Anion Gap Acidosis: Caused by the buildup of organic acids such as lactate (e.g., lactic acidosis), ketoacids (e.g., diabetic ketoacidosis), or toxins (e.g., methanol, ethylene glycol).
    • Non-Anion Gap Acidosis: Occurs when bicarbonate is lost (e.g., through the gastrointestinal tract or kidneys) or when hydrochloric acid is added to the system.
  2. Respiratory Acidosis
    • Develops due to hypoventilation, resulting in the accumulation of carbon dioxide (CO₂). Elevated CO₂ levels lower blood pH, leading to acidemia.

Mechanism of Action of Bicarbonate

Sodium bicarbonate (NaHCO₃) is a buffer that helps neutralize excess acid. When administered, it dissociates into sodium (Na⁺) and bicarbonate (HCO₃⁻). The bicarbonate ions bind with hydrogen ions (H⁺) to form carbonic acid (H₂CO₃), which the body converts into water (H₂O) and carbon dioxide (CO₂). The CO₂ is then exhaled through the lungs, helping to raise blood pH.

Indications for Bicarbonate Use

  1. Severe Metabolic Acidosis
    • Sodium bicarbonate is recommended when arterial blood pH is ≤ 7.0. The primary objective is to raise the pH to a safer level (around 7.2) to reduce the harmful effects of extreme acidemia.
  2. Lactic Acidosis with Acute Kidney Injury (AKI)
    • According to the Surviving Sepsis Campaign, endorsed by the Society of Critical Care Medicine, sodium bicarbonate may improve outcomes in patients with severe metabolic acidemia (pH ≤ 7.2) who also have AKI (AKIN stage 2 or 3). Studies suggest a survival benefit in this subgroup.
  3. Drug Intoxications
    • Sodium bicarbonate is also beneficial for certain drug overdoses, including sodium channel blockers or salicylates, where urine alkalinization enhances the elimination of the toxin.

Contraindications and Cautions

  • Lactic Acidosis Secondary to Hypoperfusion
    • Routine use of bicarbonate in lactic acidosis caused by poor tissue perfusion (e.g., immediately after cardiac surgery) is not generally recommended. Research indicates no meaningful improvement in hemodynamic status or reduction in vasopressor requirements. The Surviving Sepsis Campaign advises against using bicarbonate if pH ≥ 7.15.
  • Respiratory Acidosis
    • In respiratory acidosis, giving bicarbonate can increase CO₂ production. Since patients with respiratory acidosis already have difficulty exhaling CO₂, bicarbonate therapy can worsen the condition by raising the ventilatory burden.

Potential Adverse Effects

  • Hypernatremia
  • Hypocalcemia
  • Metabolic alkalosis if overcorrected,
  • Reduced myocardial contractility and vasomotor tone, which can further compromise circulation.


Special Focus: Lactic Acidosis Post-Cardiac Surgery

When lactic acidosis follows cardiac surgery, it is frequently tied to hypoperfusion and tissue hypoxia. The main therapeutic approach should be to restore adequate tissue perfusion and oxygenation. Sodium bicarbonate may be considered only in severe acidemia (pH ≤ 7.0) if its potential benefits outweigh the risks. Administration should be gradual, with close monitoring of blood gases and electrolytes to avoid complications like metabolic alkalosis and shifts in serum electrolytes.

Conclusion

Sodium bicarbonate is a powerful tool in the management of severe metabolic acidosis, particularly when the blood pH is below 7.0 or in patients with coexisting acute kidney injury (AKI). However, its role in lactic acidosis secondary to hypoperfusion and respiratory acidosis is generally limited or not recommended, mainly because it may not offer any real benefits and can potentially worsen the patient’s condition. As always, it is crucial to address the root cause of the acid-base disturbance—be it improving tissue perfusion in shock states or enhancing ventilation in respiratory failure—while using sodium bicarbonate judiciously.

Join the Conversation

What is your thoughts on using sodium bicarbonate? Do you have an ICU protocol or guidelines in your facility to monitor the use of sodium bicarbonate? We’d love to hear from you. Your insights can help us all continue to grow and learn together.


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Author

Omid Zad, MD
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