How to manage a patient with severe lactic acidosis?

Management of Severe Lactic Acidosis

The primary treatment for severe lactic acidosis is identifying and addressing the underlying cause, with aggressive fluid resuscitation, vasopressor support, and consideration of renal replacement therapy in refractory cases. 1

Initial Assessment and Diagnosis

• Severe lactic acidosis is defined by:

  • Blood pH < 7.35
  • Elevated blood lactate levels > 5 mmol/L
  • Anion gap acidosis
  • Increased lactate:pyruvate ratio 1

• Laboratory evaluation should include:

  • Arterial blood gases
  • Complete blood count
  • Comprehensive metabolic panel
  • Serum lactate level
  • Anion gap calculation (Na - [Cl+CO2]) 1, 2

• Abnormal values indicating severe acidosis include:

  • Increased anion gap > 16
  • Elevated aminotransferases
  • Elevated creatine phosphokinase
  • Lactic dehydrogenase
  • Lipase and amylase 2

Classification of Lactic Acidosis

1. Type A (Hypoxic): Due to tissue hypoperfusion or hypoxia

   • Caused by shock, sepsis, cardiac failure, severe trauma
   • Most common form in critically ill patients 1

2. Type B (Non-hypoxic): Occurs despite adequate tissue oxygenation

   • Medication-induced (e.g., metformin)
   • Liver dysfunction
   • Malignancies
   • Thiamine deficiency 1, 3

Treatment Algorithm

Step 1: Immediate Resuscitation

• Fluid resuscitation: 20-40 ml/kg of either 0.9% saline or 4.5% human albumin solution to correct hypovolemic shock 2
• Monitor for fluid overload: Especially in elderly patients or those with cardiac, hepatic, or renal dysfunction 1
• Vasopressor support: If hypotension persists (systolic BP < 80 mmHg) despite adequate fluid resuscitation 2
  • Norepinephrine is the first-line agent
  • Adrenaline is the second-line agent 2

Step 2: Address the Underlying Cause

• Sepsis: Appropriate antibiotics and source control
• Tissue hypoperfusion: Improve cardiac output and oxygen delivery
• Medication-induced: Discontinue offending medications (e.g., metformin) 1
• Intestinal ischemia: Consider early CT angiography if abdominal pain is present 1

Step 3: Management of Severe Acidosis

• Sodium bicarbonate administration:

  • Consider only in cases with pH < 7.15 and hemodynamic instability 2, 1
  • Initial dose: 1-2 vials (44.6-100 mEq) IV, may continue at 50 mL (44.6-50 mEq) every 5-10 minutes as indicated by arterial pH monitoring 4
  • Caution: Bicarbonate therapy can lead to:
    • Increased lactate production
    • Hypernatremia
    • Hypervolemia
    • Paradoxical intracellular acidosis 1, 3

• Renal replacement therapy:

  • Consider hemodialysis or hemofiltration for:
    • Severe, refractory lactic acidosis with hemodynamic instability
    • Metformin-associated lactic acidosis
    • Cases unresponsive to conventional therapy 1, 5

Step 4: Supportive Care and Monitoring

• Serial lactate measurements: Every 4-6 hours to assess lactate clearance 1
• Regular monitoring:
  • Arterial blood gases
  • Plasma osmolarity
  • Hemodynamics
  • Cardiac rhythm
  • Renal function 1
• Ventilatory support: For patients with respiratory failure
  • Caution: When initiating ventilation, avoid rapid rise of PCO2 even to normal levels before acidosis is partly corrected 2

Special Considerations

• Cardiogenic shock: Consider mechanical circulatory support if inotropes and IABP fail to maintain adequate perfusion 2
• Liver dysfunction: May impair lactate metabolism, requiring more aggressive intervention 1
• Alcoholic patients: At higher risk due to impaired lactate metabolism 1
• Short bowel syndrome: Monitor for D-lactic acidosis, which requires different management 1

Pitfalls to Avoid

1. Excessive bicarbonate administration: Can worsen intracellular acidosis and cause hypernatremia, hypervolemia, and decreased ionized calcium 3, 5

2. Delayed treatment of underlying cause: The most effective treatment is eliminating the triggering condition 6, 5

3. Overaggressive fluid resuscitation: Can lead to pulmonary edema, especially in patients with cardiac dysfunction 1

4. Failure to monitor response: Serial lactate measurements are essential to assess treatment efficacy 1

5. Focusing solely on pH correction: Without addressing the underlying cause, mortality remains high despite normalization of laboratory values 7