What is the treatment for metabolic acidosis?

Treatment of Metabolic Acidosis

The treatment of metabolic acidosis should target the underlying cause while providing supportive care, with sodium bicarbonate therapy indicated for severe acidosis (pH <7.1 or bicarbonate <12 mEq/L) or when rapid correction is necessary for cardiac stability. 1

Diagnostic Approach

Before initiating treatment, it's essential to identify the type and cause of metabolic acidosis:

• Calculate anion gap: High anion gap (>12 mEq/L) vs. normal anion gap
• Evaluate for common causes:
  • High anion gap: Diabetic ketoacidosis, lactic acidosis, renal failure, toxins/drugs
  • Normal anion gap: Renal tubular acidosis, diarrhea, ureterosigmoidostomy

Treatment Algorithm

1. Address the Underlying Cause

• Diabetic ketoacidosis:

  • Insulin therapy plus fluid resuscitation
  • In ketoacidosis/ketosis, initiate subcutaneous or intravenous insulin to rapidly correct hyperglycemia and metabolic derangement 2
  • Once acidosis resolves, initiate metformin while continuing insulin therapy 2

• Lactic acidosis:

  • Improve tissue perfusion and oxygenation
  • Treat shock with appropriate fluid resuscitation
  • Do not use sodium bicarbonate to treat metabolic acidosis arising from tissue hypoperfusion 2

• Chronic kidney disease:

  • Maintain serum bicarbonate at or above 22 mmol/L 2
  • Oral sodium bicarbonate (2-4 g/day or 25-50 mEq/day) can effectively increase serum bicarbonate 2

• Toxin-induced:

  • Specific antidotes when available
  • Consider sodium bicarbonate for salicylate or methanol poisoning 1

2. Sodium Bicarbonate Therapy

Indications:

• Severe metabolic acidosis (pH <7.1 or bicarbonate <12 mEq/L)
• Cardiac arrest with metabolic acidosis
• Certain drug intoxications (barbiturates, salicylates, methanol)
• Hemolytic reactions requiring urine alkalinization
• Severe diarrhea with bicarbonate loss 1

Dosing:

• Cardiac arrest: 1-2 vials (44.6-100 mEq) initially, then 50 mL (44.6-50 mEq) every 5-10 minutes as needed 1
• Less urgent metabolic acidosis: 2-5 mEq/kg over 4-8 hours 1
• Chronic kidney disease: 2-4 g/day or 25-50 mEq/day orally 2

Important Cautions:

• Avoid full correction of low bicarbonate in first 24 hours to prevent rebound alkalosis 1
• Target initial bicarbonate of about 20 mEq/L, which usually normalizes pH due to ventilatory compensation 1
• Monitor for complications: volume overload, hypertension, hypocalcemia, hypokalemia

3. Dialysis Considerations

• Consider hemodialysis for severe, refractory acidosis, especially with renal failure
• For patients on maintenance dialysis, adjust dialysate bicarbonate concentration
• Higher bicarbonate concentrations in hemodialysate (38 mmol/L) can safely increase predialysis serum bicarbonate 2

Special Populations

Children

• In diabetic ketoacidosis, fluid resuscitation should be cautious
• Avoid sodium bicarbonate in pediatric DKA unless severe acidosis is compromising cardiac function
• In children with shock and coma, human albumin solution may be preferred over saline for volume resuscitation 2

Chronic Kidney Disease

• Regular monitoring of serum bicarbonate (monthly) 2
• Maintain serum bicarbonate ≥22 mmol/L 2
• Correction of acidemia improves serum albumin, decreases protein degradation, and increases plasma concentrations of essential amino acids 2

Potential Pitfalls

1. Overcorrection: Rapid or excessive bicarbonate administration can lead to:

   • Paradoxical CSF acidosis
   • Hypokalemia
   • Hypocalcemia
   • Volume overload
   • Hypernatremia

2. Inadequate monitoring: Follow arterial or venous blood gases and electrolytes during treatment

3. Treating the number, not the patient: Clinical status should guide therapy alongside laboratory values

4. Ignoring the underlying cause: Bicarbonate therapy alone without addressing the primary disorder will not resolve the acidosis

Remember that metabolic acidosis is often a manifestation of an underlying disease process, and successful management requires identification and treatment of the primary disorder while providing appropriate supportive care.