Management of Severe Metabolic Acidosis
For severe metabolic acidosis (pH < 7.2), sodium bicarbonate administration is indicated, particularly when acidosis is associated with hemodynamic instability, along with aggressive treatment of the underlying cause. 1, 2
Initial Assessment and Management
- Severe metabolic acidosis is defined as pH < 7.2 with base deficit > 10 mmol/L or bicarbonate < 12 mmol/L 3, 1
- Immediate assessment should include arterial blood gas analysis, serum electrolytes, calculation of anion gap, and evaluation of vital signs 4
- Identify and treat the underlying cause as the primary intervention (e.g., insulin for diabetic ketoacidosis, volume restoration in shock) 2
- For pH < 7.15 with hemodynamic instability, sodium bicarbonate administration is recommended 2
Specific Interventions Based on Severity
For pH < 7.1 (Extreme Acidosis)
- Immediate sodium bicarbonate administration is indicated 1, 2
- Patients with extreme acidosis (pH < 7.0) have a mortality rate of approximately 67.5%, significantly better than the predicted 93.6%, justifying aggressive intervention 5
- Consider intubation and mechanical ventilation for respiratory compensation if respiratory distress is present 3
For pH 7.1-7.2
- Sodium bicarbonate therapy should be considered, especially with hemodynamic compromise 3, 2
- Target correction rate should avoid rapid changes that could lead to complications such as hypernatremia, hyperosmolarity, or paradoxical intracellular acidosis 1
Special Considerations by Etiology
Lactic Acidosis
- In hypoperfusion-induced lactic acidosis with pH < 7.15, sodium bicarbonate therapy is recommended despite limited evidence of mortality benefit 3
- Focus on improving tissue perfusion with fluid resuscitation and vasopressors as appropriate 3
- In cases of severe lactic acidosis from carbon monoxide poisoning with pH < 7.20, consider empiric treatment for concomitant cyanide poisoning if exposure was from a house fire 3
Diabetic Ketoacidosis
- Insulin therapy and volume repletion are the cornerstones of treatment 2
- Bicarbonate therapy is indicated when pH < 7.1 with severe acidosis 2
- Patients with diabetic ketoacidosis have better outcomes (22% mortality with extreme acidosis) compared to other causes 5
Renal Failure-Associated Acidosis
- Consider renal replacement therapy when severe acidosis is present with renal failure 2
- For chronic kidney disease patients, maintain serum bicarbonate ≥ 22 mEq/L 6
Fluid Management in Severe Acidosis
- In children with severe malaria and acidosis, volume resuscitation with 20-40 ml/kg of either 0.9% saline or 4.5% human albumin solution safely corrects hemodynamic features of shock 3
- For patients with coma and shock, human albumin solution may be preferable to saline 3
- Monitor urine output (target > 1 ml/kg/hour) as a guide to fluid management 3
Ventilatory Support
- Consider non-invasive ventilation when pH < 7.35 and pCO2 > 6.5 kPa despite optimal medical therapy 3
- For patients requiring mechanical ventilation, use low tidal volume strategy (6-8 ml/kg) 1
- Be cautious when initiating ventilation in patients with severe metabolic acidosis who are compensating with hyperventilation - avoid rapid rise in pCO2 3
Monitoring and Reassessment
- Serial arterial blood gases should be performed to assess response to therapy 4
- Monitor electrolytes closely, particularly potassium, calcium, and sodium 1
- Worsening physiological parameters, particularly pH and respiratory rate, indicate the need to escalate management 1
Common Pitfalls to Avoid
- Avoid excessive bicarbonate administration, which can cause hypernatremia, hyperosmolarity, and paradoxical intracellular acidosis 1
- Don't delay treatment of the underlying cause while focusing solely on pH correction 2
- Be cautious with fluid administration in patients with heart failure, as volume overload may worsen respiratory function 1
- Avoid rapid correction of severe acidosis in patients with acute liver failure as this may exacerbate intracranial hypertension 1