What is the treatment approach for a patient with lactic acidosis, potentially caused by medications such as metformin (biguanide), and how should it be managed?

Treatment of Lactic Acidosis

The primary treatment of lactic acidosis is identifying and aggressively treating the underlying cause—sodium bicarbonate should NOT be used for pH ≥7.15 as it does not improve outcomes and may cause harm. 1

Immediate Management Priorities

1. Identify and Treat the Underlying Cause

This is the cornerstone of management and takes absolute priority over all other interventions. 1

For Type A Lactic Acidosis (Tissue Hypoxia):

• Restore tissue perfusion with aggressive fluid resuscitation (15-20 mL/kg/h isotonic saline initially) if shock is present 1
• Treat sepsis aggressively with source control, antibiotics within 3 hours, and hemodynamic support per Surviving Sepsis Campaign protocols 1
• Consider vasopressors (norepinephrine first-line, epinephrine second-line) if hypotension persists despite fluid resuscitation 2

For Medication-Induced Lactic Acidosis:

• Discontinue offending medications immediately 1:
  • Metformin: Stop immediately in any patient with lactic acidosis, especially with renal impairment, sepsis, or acute illness 3
  • NRTIs (stavudine, didanosine): Discontinue immediately in HIV patients—this has high mortality without intervention 1

2. Supportive Care Measures

Hemodialysis for Metformin-Associated Lactic Acidosis (MALA):

• Prompt hemodialysis is recommended for suspected or confirmed MALA 3
• Metformin is dialyzable with clearance up to 170 mL/min under good hemodynamic conditions 3
• Hemodialysis often results in reversal of symptoms and recovery 3
• Continuous renal replacement therapy (CRRT) is preferred in hemodynamically unstable patients as it corrects acidosis without risk of hypernatremia or fluid overload 4, 5

Thiamine Supplementation:

• Consider thiamine to address pyruvate dehydrogenase dysfunction 1

The Bicarbonate Controversy: When NOT to Use It

The Surviving Sepsis Campaign explicitly recommends AGAINST using sodium bicarbonate to improve hemodynamics or reduce vasopressor requirements in hypoperfusion-induced lactic acidemia with pH ≥7.15. 1

Why bicarbonate is harmful:

• Does not improve hemodynamics or cardiovascular function 1, 6
• May increase lactate production 1
• Causes hypernatremia and volume overload 1
• Generates CO₂ 1
• Has never been shown to improve survival 1, 6

Exception: Bicarbonate may be considered only when pH <7.15 in the setting of severe acidosis with catecholamine receptor resistance-induced hypotension 2

Special Clinical Scenarios

D-Lactic Acidosis (Short Bowel Syndrome)

• Restrict mono/oligosaccharides 1
• Encourage polysaccharides (starch) 1
• Give thiamine supplements 1
• Administer broad-spectrum antibiotics 1

Metformin-Associated Lactic Acidosis

Risk factors to recognize:

• Renal impairment (eGFR <30 mL/min/1.73 m²) 3
• Acute kidney injury from any cause 1
• Sepsis or systemic infection with hemodynamic instability 1
• Hypoxic states 1
• Severe illness, vomiting, or dehydration 2

Management algorithm:

1. Discontinue metformin immediately 3
2. Institute general supportive measures promptly in hospital setting 3
3. Initiate prompt hemodialysis or CRRT to correct acidosis and remove accumulated metformin 3, 4, 5

HIV Patients on NRTIs

• Discontinue NRTIs immediately (especially stavudine and didanosine) 1
• High mortality without intervention 1

Monitoring and Laboratory Targets

Key laboratory values:

• Lactate >5 mmol/L with anion gap acidosis indicates metformin-associated lactic acidosis 3
• Metformin plasma levels generally >5 mcg/mL in MALA 3
• pH <7.3 with lactate >2 mmol/L confirms lactic acidosis 1

Serial monitoring:

• Repeat lactate within 6 hours to evaluate trend 1
• Monitor electrolytes closely during renal replacement therapy 1

Common Pitfalls to Avoid

• DO NOT delay treatment while waiting for lactate levels—treat the underlying cause immediately 1
• DO NOT use sodium bicarbonate unless pH <7.15 2, 1
• DO NOT continue metformin in any patient with acute illness, sepsis, or renal dysfunction 3
• DO NOT ignore subtle early symptoms (nonspecific GI symptoms, dyspnea, weakness, myalgias) that often precede severe acidosis 1
• DO NOT delay hemodialysis in suspected MALA—it is the definitive treatment 3, 4, 5

Patient Education

Educate patients and families about symptoms of lactic acidosis: malaise, myalgias, abdominal pain, respiratory distress, increased somnolence 3. Instruct them to discontinue metformin and report symptoms immediately to their healthcare provider 3.