What is the appropriate treatment for a patient with elevated lactic acid (lactic acidosis), potentially due to underlying conditions such as diabetes, liver or kidney disease, or medication use?

Treatment of Elevated Lactic Acid (Lactic Acidosis)

The primary treatment of lactic acidosis is identifying and aggressively treating the underlying cause—not administering sodium bicarbonate, which lacks evidence for improving outcomes and may cause harm. 1

Immediate Diagnostic Priorities

When confronted with elevated lactate, your first task is determining the type and cause:

• Measure arterial pH and calculate anion gap (Na - [Cl+CO2]): pH <7.3 with anion gap >16 confirms lactic acidosis 1
• Lactate thresholds matter: >2 mmol/L is elevated, >5 mmol/L is abnormal, >10 mmol/L is life-threatening 1
• Distinguish Type A (tissue hypoxia) from Type B (metabolic/drug-induced): Type A results from shock, sepsis, or circulatory failure; Type B occurs without hypoxia from medications, liver disease, or metabolic disturbances 1

Critical Pitfall to Avoid

Do NOT ignore elevated lactate even without hypotension—persistent hyperlactatemia ≥2 mmol/L indicates tissue hypoperfusion or organ dysfunction and meets criteria for severe sepsis, even with normal blood pressure. 1

Step 1: Restore Tissue Perfusion (Type A Lactic Acidosis)

If shock or hypoperfusion is present:

• Fluid resuscitation: Administer 15-20 mL/kg/h isotonic saline initially (1-2 L over 60-90 minutes) 1
• Vasopressors if hypotension persists: Norepinephrine first-line, epinephrine second-line 1
• Treat sepsis aggressively: Obtain blood cultures and administer antibiotics within 3 hours, achieve source control 1
• Repeat lactate measurement within 6 hours to assess response 1

Step 2: Discontinue Offending Medications Immediately

Medication-induced lactic acidosis requires immediate drug cessation:

• Metformin: Stop immediately if patient has sepsis, acute kidney injury, dehydration, or any serious intercurrent illness. Risk dramatically increases with eGFR <30 mL/min/1.73m² (contraindicated) or eGFR 30-45 (requires dose reduction to 1000 mg daily). 1
• Nucleoside reverse transcriptase inhibitors (NRTIs): Discontinue stavudine and didanosine immediately in HIV patients—mortality is high without intervention. Incidence is 1.3 cases/1000 person-years of NRTI exposure. 1

Common Pitfall

Patients must be explicitly counseled to stop metformin during any serious illness—vomiting, dehydration, or systemic infection with hemodynamic instability all mandate immediate discontinuation. 1

Step 3: Address Specific Underlying Causes

For D-Lactic Acidosis (Short Bowel Syndrome)

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

For Suspected Mesenteric Ischemia

If lactate >2 mmol/L with abdominal pain and elevated urea, suspect acute mesenteric ischemia immediately:

• Order CT angiography (CTA) urgently—do NOT delay, as diagnostic delay is the dominant mortality factor (30-70%) 1
• Lactate >2 mmol/L predicts irreversible intestinal ischemia (HR 4.1,95% CI 1.4-11.5) 1

For Renal Impairment Contributing to Lactate Accumulation

• Kidneys contribute to lactate clearance; impairment reduces removal 1
• Monitor eGFR at least annually in metformin users, every 3-6 months if eGFR <60 mL/min/1.73m² 1

For Liver Disease

• Liver is the major site of lactate removal through gluconeogenesis—hepatic impairment dramatically reduces clearance 1

Step 4: The Bicarbonate Controversy—When NOT to Use It

The Surviving Sepsis Campaign explicitly recommends AGAINST sodium bicarbonate for pH ≥7.15 in hypoperfusion-induced lactic acidemia. 1

Why Bicarbonate Fails and May Harm:

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

The Only Exception:

Consider bicarbonate only when pH <7.15 with severe acidosis causing catecholamine receptor resistance and refractory hypotension. 1 The FDA label supports use in "severe primary lactic acidosis" where rapid increase in plasma CO₂ is crucial, but this should be stepwise and monitored. 2

If bicarbonate is used: Administer 2-5 mEq/kg over 4-8 hours, monitor arterial pH and blood gases closely, and do NOT attempt full correction in first 24 hours due to risk of overshoot alkalosis. 2

Step 5: Consider Hemodialysis for Metformin-Associated Lactic Acidosis

Hemodialysis is the definitive treatment for metformin-associated lactic acidosis (MALA) and often reverses symptoms. 1 This is particularly important because metformin clearance decreases by ~75% when eGFR drops to 60 mL/min/1.73m². 1

Step 6: Supportive Care Measures

• Thiamine supplementation: Consider for pyruvate dehydrogenase dysfunction, especially in alcoholism or malnutrition 1
• Monitor electrolytes closely: Correct hyperkalemia, hypocalcemia, and other abnormalities 1
• Avoid medications with long half-lives if mechanical ventilation required—use propofol or dexmedetomidine 3

Special Clinical Scenarios Requiring Heightened Vigilance

COVID-19 and Metformin

COVID-19 infection increases lactic acidosis risk in metformin users (adjusted HR 4.46)—consider stopping metformin in infected patients. 1

Rhabdomyolysis-Induced Lactic Acidosis

• Damaged muscle undergoes anaerobic metabolism producing lactate 1
• Monitor creatine kinase, myoglobin, and correct electrolyte abnormalities (especially hyperkalemia) 1

Hypophosphatemia with Lactic Acidosis

Refeeding syndrome and prolonged dialysis (up to 80% of ICU patients) cause severe hypophosphatemia triggering lactic acidosis:

• Replace phosphate IV (0.16 mmol/kg at 1-3 mmol/h) if <0.32 mmol/L 1
• Advance nutrition slowly, monitor electrolytes daily during first week 1

Algorithm Summary

1. Confirm diagnosis: pH <7.3, lactate >2 mmol/L, anion gap >16 1
2. Type A (shock/hypoxia): Fluid resuscitation 15-20 mL/kg/h, vasopressors if needed, treat sepsis within 3 hours 1
3. Type B (metabolic/drug): Stop metformin/NRTIs immediately, consider hemodialysis for MALA 1
4. Avoid bicarbonate unless pH <7.15 with refractory hypotension 1
5. Repeat lactate in 6 hours to assess response 1
6. Consider specific causes: Mesenteric ischemia (CTA urgently), D-lactic acidosis (diet modification, thiamine, antibiotics), refeeding syndrome (phosphate replacement) 1