Treatment of Metabolic Acidosis
The treatment of metabolic acidosis should be primarily directed at correcting the underlying cause while maintaining serum bicarbonate levels at or above 22 mmol/L to prevent adverse clinical outcomes related to morbidity and mortality. 1
Diagnostic Approach
Before initiating treatment, identify the type and cause of metabolic acidosis:
- Measure serum bicarbonate, pH, anion gap, and electrolytes
- Calculate anion gap: [(Na+ + K+) - (Cl- + HCO3-)] 2
- Determine if high anion gap (>12 mEq/L) or normal anion gap acidosis
- Assess for underlying causes (renal failure, diabetic ketoacidosis, lactic acidosis, toxin ingestion, diarrhea)
Treatment Algorithm
Step 1: Address the Underlying Cause
- Diabetic ketoacidosis: Insulin therapy, fluid resuscitation, electrolyte replacement 1
- Renal failure: Dialysis if severe or refractory 1
- Lactic acidosis: Improve tissue perfusion, treat sepsis or shock 3
- Toxin ingestion: Specific antidotes, enhanced elimination 3
- Diarrhea: Fluid and electrolyte replacement 1
Step 2: Bicarbonate Therapy
For severe metabolic acidosis (pH <7.2 or bicarbonate <12 mEq/L):
- Intravenous sodium bicarbonate administration is indicated 3
- Initial dosing:
- Monitor arterial blood gases and electrolytes during treatment
- Target initial correction to bicarbonate of approximately 20 mEq/L within first 24 hours 3
- Avoid complete correction in first 24 hours to prevent overshoot alkalosis 3
Step 3: Special Considerations
For Chronic Kidney Disease:
- Maintain serum bicarbonate ≥22 mmol/L 1
- Oral sodium bicarbonate supplementation: 2-4 g/day (25-50 mEq/day) 1
- Consider higher dialysate bicarbonate concentrations (38 mmol/L) for hemodialysis patients 1
For Diabetic Ketoacidosis:
- Fluid resuscitation with isotonic saline (15-20 ml/kg/hr initially) 1
- Insulin therapy (IV or subcutaneous based on severity) 1
- Potassium replacement (2/3 KCl and 1/3 KPO4) once renal function is assured 1
- Bicarbonate therapy is generally not recommended for DKA unless pH is extremely low 1
For Children with Metabolic Acidosis:
- Volume resuscitation with 20-40 ml/kg of 0.9% saline or 4.5% albumin solution for shock 1
- Consider 4.5% albumin for children with coma and shock 1
- Monitor for respiratory compensation; avoid rapid rise in PCO2 during ventilation 1
Monitoring and Adjustment
- Serial measurements of arterial or venous blood gases
- Monitor electrolytes, especially potassium (acidosis correction can lower potassium) 2
- Adjust therapy based on clinical response and laboratory values
- For chronic therapy, monitor for complications of bicarbonate therapy (volume overload, hypertension, hypocalcemia)
Potential Complications of Treatment
- Volume overload from sodium bicarbonate administration
- Hypocalcemia from rapid alkalinization
- Hypokalemia during correction of acidosis
- Paradoxical CNS acidosis with rapid bicarbonate administration
- Overshoot alkalosis if correction is too aggressive 3
Clinical Benefits of Treating Metabolic Acidosis
Correction of metabolic acidosis provides several benefits:
- Improved bone health and reduced bone resorption 4
- Decreased muscle protein degradation 4
- Improved insulin sensitivity 4
- Enhanced growth in children 4
- Potentially slowed progression of kidney disease 5
- Improved cardiovascular function in severe acidosis 3
The approach to metabolic acidosis must be tailored to the severity, acuity, and underlying cause of the condition, with the primary goal of addressing the underlying disorder while preventing complications associated with chronic acidosis.