What is the treatment for metabolic acidosis?

Treatment of Metabolic Acidosis

The treatment of metabolic acidosis must be directed at correcting the underlying cause rather than routine bicarbonate administration, as sodium bicarbonate has not demonstrated mortality benefit in most acute organic acidoses and may worsen intracellular acidosis. 1

Etiology-Based Treatment Approach

The cornerstone of managing metabolic acidosis is identifying and treating the underlying disorder:

Diabetic Ketoacidosis (DKA)

• Focus on insulin therapy, fluid resuscitation, and electrolyte replacement as the primary treatment. 1
• Restoration of circulatory volume and tissue perfusion is the primary goal. 1
• Continuous intravenous insulin is the standard of care for critically ill and mentally obtunded patients. 1
• Bicarbonate administration has NOT been shown to improve resolution of acidosis or time to discharge in DKA. 1
• Bicarbonate may be beneficial ONLY in patients with pH < 6.9 (Grade C recommendation). 2
• For pH 6.9-7.0: infuse 50 mmol sodium bicarbonate in 200 mL sterile water at 200 mL/h. 1, 3
• For pH < 6.9: infuse 100 mmol sodium bicarbonate in 400 mL sterile water at 200 mL/h. 1, 3

Lactic Acidosis and Sepsis

• The Surviving Sepsis Campaign explicitly recommends AGAINST sodium bicarbonate for hypoperfusion-induced lactic acidemia when pH ≥ 7.15. 1, 3
• The only effective treatment for organic acidosis is cessation of acid production via improvement of tissue oxygenation. 4
• Two blinded randomized controlled trials showed no difference in hemodynamic variables or vasopressor requirements comparing bicarbonate versus equimolar saline. 1

Chronic Kidney Disease (CKD)

• Treat CKD-associated acidosis when serum bicarbonate is consistently < 18 mmol/L to prevent bone and muscle metabolism abnormalities. 1
• Oral sodium bicarbonate 2-4 g/day (25-50 mEq/day) can effectively increase serum bicarbonate concentrations. 1
• Maintain serum bicarbonate at or above 22 mmol/L in maintenance dialysis patients. 1
• Correction of acidemia has been associated with increased serum albumin, decreased protein degradation rates, and increased plasma concentrations of branched chain amino acids. 1

Acute Kidney Injury with Severe Acidosis

• Hemodialysis is the definitive treatment for patients with severe acidosis (pH < 7.20) and acute kidney injury. 1
• Dialysis should not be delayed while attempting medical management, as the acidosis is refractory to conservative measures. 1
• Patients require ICU-level care with nephrology consultation for urgent dialysis. 1

Sodium Bicarbonate Therapy: When and How

Specific Indications for Bicarbonate Administration

Bicarbonate is indicated ONLY in these specific scenarios:

• Severe metabolic acidosis with pH < 7.0-7.1 1, 3, 5
• Life-threatening hyperkalemia (as temporizing measure while definitive therapy initiated) 1, 3
• Tricyclic antidepressant overdose with QRS widening > 120 ms (Class I recommendation) 1, 3
• Sodium channel blocker toxicity with cardiotoxicity 1, 3
• Documented metabolic acidosis in maintenance dialysis patients 1
• Tumor lysis syndrome with documented metabolic acidosis 1

Dosing and Administration

Initial Bolus:

• Adults: 1-2 mEq/kg IV (typically 50-100 mL of 8.4% solution) given slowly over several minutes. 3, 5
• Children: 1-2 mEq/kg IV given slowly. 2, 3
• Newborns: Use only 0.5 mEq/mL (4.2%) concentration. 1, 3

For Cardiac Arrest:

• Rapid intravenous dose of 44.6 to 100 mEq (one to two 50 mL vials) may be given initially. 5
• Continue at 50 mL (44.6 to 50 mEq) every 5-10 minutes if necessary as indicated by arterial pH and blood gas monitoring. 5

For TCA/Sodium Channel Blocker Toxicity:

• Initial bolus: 50-150 mEq using hypertonic solution (1000 mEq/L). 1, 3
• Follow with continuous infusion of 150 mEq/L solution at 1-3 mL/kg/h. 1, 3
• Target arterial pH 7.45-7.55. 1

For Less Urgent Metabolic Acidosis:

• 2-5 mEq/kg body weight over 4-8 hours depending on severity. 5
• Therapy should be planned in stepwise fashion since response is not precisely predictable. 5

Critical Monitoring Requirements

Monitor every 2-4 hours during active therapy: 1, 3

• Arterial blood gases (pH, PaCO2, bicarbonate)
• Serum electrolytes (sodium, potassium, chloride)
• Ionized calcium
• Anion gap

Target Parameters:

• Target pH: 7.2-7.3, NOT complete normalization 1, 3
• Serum sodium: maintain < 150-155 mEq/L 1, 3
• Avoid pH > 7.50-7.55 1, 3

Common Pitfalls and Critical Safety Considerations

Absolute Contraindications and Cautions

DO NOT use bicarbonate in these situations:

• Hypoperfusion-induced lactic acidemia with pH ≥ 7.15 1, 3
• Routine use in cardiac arrest (not recommended) 1, 3
• DKA with pH ≥ 7.0 2, 1
• Respiratory acidosis without adequate ventilation 1, 3

Adverse Effects to Monitor

Sodium bicarbonate can cause: 1, 3

• Extracellular alkalosis with leftward shift of oxyhemoglobin curve
• Hypernatremia and hyperosmolarity
• Excess CO2 production causing paradoxical intracellular acidosis
• Decreased ionized calcium (worsening cardiac contractility)
• Hypokalemia (due to intracellular potassium shift)
• Inactivation of simultaneously administered catecholamines
• Sodium and fluid overload

Administration Precautions

Critical safety measures: 1, 3

• Ensure effective ventilation BEFORE administering bicarbonate (ventilation needed to eliminate excess CO2)
• Never mix with calcium-containing solutions or vasoactive amines
• Flush IV line with normal saline before and after bicarbonate administration
• Use 4.2% concentration for children under 2 years (dilute 8.4% solution 1:1 with normal saline)

Electrolyte Management

Potassium monitoring is essential: 1, 3

• Acidosis causes hyperkalemia due to transcellular potassium shift
• Correction of acidosis (with insulin, bicarbonate, or volume expansion) decreases serum potassium
• Monitor potassium every 2-4 hours and supplement as needed
• Hypokalemia can develop rapidly during bicarbonate therapy

Special Clinical Scenarios

Severe Malaria in Children

• Metabolic acidosis resolves with correction of hypovolemia and treatment of anemia by adequate blood transfusion. 1
• No evidence supports sodium bicarbonate use. 1

Renal Tubular Acidosis in Children

• Normalization of serum bicarbonate is important for normal growth parameters. 1

Continuous Renal Replacement Therapy (CRRT)

• Either lactate or bicarbonate can be used as buffer in most CRRT patients. 1
• Bicarbonate is preferred in patients with lactic acidosis and/or liver failure. 1