How to manage metabolic acidosis with lactic acidosis?

Management of Metabolic Acidosis with Lactic Acidosis

In patients with lactic acidosis, bicarbonate therapy should be reserved for severe acidosis with pH < 7.15, while the primary focus should be on treating the underlying cause and optimizing tissue perfusion. 1

Initial Assessment and Classification

• Determine the severity of acidosis through:

  • Arterial blood gases (pH, PaCO2)
  • Serum electrolytes with calculated anion gap
  • Lactate levels
  • Serum ketones
  • Blood glucose

• Identify the underlying cause:

  • Type A lactic acidosis: tissue hypoxia (shock, severe hypoxemia)
  • Type B lactic acidosis: metabolic disorders, medications, liver failure

Treatment Algorithm

Step 1: Address the Underlying Cause

• Restore tissue perfusion in shock states
• Optimize oxygenation and ventilation
• Discontinue offending medications (metformin, etc.)
• Treat infections if present

Step 2: Manage Acidosis Based on pH

For pH ≥ 7.15:

• Do not administer sodium bicarbonate 1
• Focus on treating underlying cause
• Ensure adequate fluid resuscitation
• Optimize hemodynamics to improve tissue perfusion

For pH < 7.15:

• Consider sodium bicarbonate therapy 1, 2
• Initial IV dose: 1-2 mEq/kg 2
• For ongoing management: 2-5 mEq/kg over 4-8 hours 1
• Target total CO2 content of about 20 mEq/L at the end of the first day 1

Special Considerations

Fluid Management

• In shock patients, use isotonic saline (0.9% NaCl) at 15-20 ml/kg/h initially to restore intravascular volume 3
• Subsequent fluid choice depends on hydration status and electrolytes
• Avoid volume overload, especially in patients with acute lung injury 3

Renal Replacement Therapy

• For patients with lactic acidosis and acute kidney injury:
  • Bicarbonate is preferred as buffer in CRRT for patients with lactic acidosis 3
  • Avoid lactate-containing dialysate/replacement fluids as they may worsen acidosis in patients with lactic acidosis or liver failure 3

Monitoring

• Regular assessment of:
  • Arterial blood gases
  • Serum electrolytes (especially potassium, calcium, sodium)
  • Hemodynamic parameters
  • ECG for arrhythmias
  • Mental status

Important Caveats

• Bicarbonate therapy can cause complications:

  • Hypernatremia (avoid serum sodium >150-155 mEq/L) 1
  • Paradoxical intracellular acidosis
  • Decreased ionized calcium
  • Volume overload

• Alternative buffer agents:

  • THAM (tromethamine) may be considered for patients with hypernatremia or mixed acidosis with high PaCO2 1

• Avoid therapies that may worsen lactic acidosis:

  • Sodium acetate has been reported to cause lactic acidosis in some patients 4
  • Excessive bicarbonate administration may increase lactate production 5

• Prognosis depends on treating the underlying cause:

  • No specific therapy targeting lactate levels has been shown to reduce mortality 6
  • The severity of lactic acidosis correlates with overall oxygen debt and survival 7

The cornerstone of treatment remains prompt recognition and management of the underlying cause of lactic acidosis, with judicious use of bicarbonate only in cases of severe acidosis (pH < 7.15).