What are the indications, contraindications, dosage, and formulations for intravenous (IV) sodium bicarbonate use in patients with severe metabolic acidosis?

IV Sodium Bicarbonate in Metabolic Acidosis

Indications for IV Sodium Bicarbonate

Sodium bicarbonate should be administered for severe metabolic acidosis with pH < 7.1 and base deficit < -10, or for specific conditions including life-threatening hyperkalemia, tricyclic antidepressant/sodium channel blocker overdose, and documented metabolic acidosis in cardiac arrest after initial epinephrine fails. 1, 2

Primary Indications

• Severe metabolic acidosis with pH < 7.1 AND base excess < -10 is the threshold for bicarbonate therapy in critically ill patients 1
• Life-threatening cardiotoxicity from tricyclic antidepressant or sodium channel blocker poisoning with QRS prolongation > 120 ms (Class I recommendation) 1
• Life-threatening hyperkalemia as a temporizing measure to shift potassium intracellularly while definitive therapy is initiated 1
• Cardiac arrest only after the first dose of epinephrine has been ineffective, with documented severe acidosis 1, 2
• Diabetic ketoacidosis with pH < 6.9 (bicarbonate may be beneficial; not indicated if pH ≥ 7.0) 1

Specific Disease States

• Severe renal disease, uncontrolled diabetes, circulatory insufficiency due to shock or severe dehydration, extracorporeal circulation, and severe primary lactic acidosis are FDA-approved indications 2
• Drug intoxications including barbiturates, salicylates, and methyl alcohol poisoning requiring urinary alkalinization 2
• Severe diarrhea with significant bicarbonate loss 2
• Rhabdomyolysis with myoglobinuria to alkalinize urine and prevent acute tubular necrosis 1

Contraindications and When NOT to Use Bicarbonate

Do not administer sodium bicarbonate for hypoperfusion-induced lactic acidemia when pH ≥ 7.15, as multiple trials show no benefit and potential harm. 1, 3

Absolute Contraindications

• Hypoperfusion-induced lactic acidemia with pH ≥ 7.15 in sepsis (strong evidence against use from Surviving Sepsis Campaign) 1
• Routine use in cardiac arrest without specific indications 1
• Respiratory acidosis (treat with ventilation, not bicarbonate) 1
• Metabolic acidosis from tissue hypoperfusion as routine therapy 1

Relative Contraindications

• Diabetic ketoacidosis with pH ≥ 7.0 (bicarbonate not necessary) 1
• Inadequate ventilation (bicarbonate produces CO2 that must be eliminated; giving it without adequate ventilation causes paradoxical intracellular acidosis) 1
• Severe hypernatremia or hyperosmolarity (bicarbonate solutions are hypertonic) 1, 2

Dosage and Administration

Initial Bolus Dosing

For adults with severe metabolic acidosis, administer 1-2 mEq/kg (50-100 mL of 8.4% solution) IV slowly over several minutes, with repeat dosing guided by arterial blood gas analysis every 2-4 hours. 1, 2

• Adults: 1-2 mEq/kg IV (typically 50-100 mEq or 50-100 mL of 8.4% solution) given slowly 1, 2
• Children: 1-2 mEq/kg IV given slowly 1
• Newborn infants: Use only 0.5 mEq/mL (4.2%) concentration; dilute 8.4% solution 1:1 with normal saline or sterile water 1
• Pediatric patients < 2 years: Dilute 8.4% solution 1:1 with normal saline to achieve 4.2% concentration 1

Specific Clinical Scenarios

• Cardiac arrest: Initial dose of 50 mL (44.6-50 mEq), repeated every 5-10 minutes as indicated by arterial pH monitoring 2
• TCA/sodium channel blocker toxicity: Initial bolus of 50-150 mEq using hypertonic solution (1000 mEq/L), titrated to resolution of QRS prolongation 1
• Diabetic ketoacidosis with pH < 6.9: 100 mmol sodium bicarbonate in 400 mL sterile water at 200 mL/h 1
• Diabetic ketoacidosis with pH 6.9-7.0: 50 mmol sodium bicarbonate in 200 mL sterile water at 200 mL/h 1

Continuous Infusion

For ongoing alkalinization needs, prepare a 150 mEq/L solution and infuse at 1-3 mL/kg/hour, targeting pH 7.2-7.3, not complete normalization. 1

• Maintenance infusion: 150 mEq/L solution at 1-3 mL/kg/hour for sodium channel blocker toxicity or ongoing severe acidosis 1
• Target pH: 7.2-7.3 (avoid complete normalization to pH > 7.50-7.55) 1
• Maximum daily dose: Generally 2-5 mEq/kg over 4-8 hours for less urgent metabolic acidosis 2

Formulations and Concentrations

Available Concentrations

• 8.4% solution (hypertonic): 1 mEq/mL or 1000 mEq/L; standard adult formulation 1, 2
• 4.2% solution (isotonic when diluted): 0.5 mEq/mL; required for newborns and infants < 2 years 1
• No commercially available isotonic bicarbonate solutions exist in the United States, requiring pharmacy compounding and creating risk for preparation errors 1

Preparation Guidelines

• For pediatric patients < 2 years: Dilute 8.4% solution 1:1 with normal saline or sterile water to achieve 4.2% concentration 1
• For continuous infusion: Dilute to 150 mEq/L solution (approximately 1.26% concentration) 1
• Never mix with calcium-containing solutions (causes precipitation) 1
• Never mix with vasoactive amines (causes inactivation of catecholamines) 1

Critical Monitoring Requirements

Monitor arterial blood gases, serum electrolytes (sodium, potassium, ionized calcium), and hemodynamics every 2-4 hours during active bicarbonate therapy. 1

Essential Parameters

• Arterial blood gases: Check pH, PaCO2, and bicarbonate every 2-4 hours 1
• Serum sodium: Target < 150-155 mEq/L (avoid hypernatremia) 1
• Serum potassium: Monitor closely as bicarbonate shifts potassium intracellularly, causing hypokalemia requiring replacement 1
• Ionized calcium: Monitor especially with doses > 50-100 mEq, as bicarbonate decreases ionized calcium 1
• Cardiac rhythm: Especially QRS duration in toxicity cases 1

Treatment Goals

• Target pH: 7.2-7.3, not complete normalization 1, 2
• Avoid pH > 7.50-7.55 (excessive alkalemia) 1
• Avoid serum sodium > 150-155 mEq/L (hypernatremia) 1
• Ensure adequate ventilation to eliminate excess CO2 produced by bicarbonate 1

Adverse Effects and Safety Considerations

Major Complications

• Hypernatremia and hyperosmolarity from hypertonic solutions 1, 2
• Paradoxical intracellular acidosis from excess CO2 production if ventilation is inadequate 1
• Hypokalemia from intracellular potassium shift (requires potassium supplementation) 1
• Hypocalcemia (decreased ionized calcium affecting cardiac contractility) 1
• Extracellular alkalosis shifting the oxyhemoglobin curve and inhibiting oxygen release 1
• Inactivation of simultaneously administered catecholamines 1
• Sodium and fluid overload 1
• Increased lactate production (paradoxical effect) 1

Administration Precautions

• Flush IV line with normal saline before and after bicarbonate to prevent catecholamine inactivation 1
• Administer slowly over several minutes, not as rapid bolus 1, 2
• Ensure effective ventilation is established first before giving bicarbonate 1
• Limit rate to no more than 8 mEq/kg/day in neonates and children < 2 years 1

Clinical Decision Algorithm

Step 1: Assess Severity and Etiology

• If pH ≥ 7.15 in sepsis/lactic acidosis: Do NOT give bicarbonate 1
• If pH 7.0-7.15: Consider bicarbonate only in specific contexts (hyperkalemia, toxicity, acute kidney injury) 1
• If pH < 7.0-7.1 with base excess < -10: Bicarbonate is indicated 1

Step 2: Ensure Prerequisites

• Confirm adequate ventilation or plan immediate intubation (bicarbonate produces CO2) 1
• Optimize hemodynamics and treat underlying cause (bicarbonate buys time but doesn't treat the disease) 1
• Check for specific indications (TCA overdose, hyperkalemia, cardiac arrest after failed epinephrine) 1

Step 3: Administer and Monitor

• Give initial bolus: 1-2 mEq/kg IV slowly 1, 2
• Recheck ABG in 2-4 hours to guide further dosing 1
• Target pH 7.2-7.3, not complete normalization 1
• Monitor sodium, potassium, and ionized calcium every 2-4 hours 1

Step 4: Adjust or Discontinue

• Stop bicarbonate when: pH reaches 7.2-7.3, hemodynamic stability achieved, hypernatremia develops (Na > 150-155 mEq/L), or excessive alkalemia occurs (pH > 7.50-7.55) 1
• Continue infusion if needed: Use 150 mEq/L solution at 1-3 mL/kg/hour for ongoing severe acidosis or toxicity 1

Special Populations

Chronic Kidney Disease

• Oral sodium bicarbonate 2-4 g/day (25-50 mEq/day) to maintain serum bicarbonate ≥ 22 mmol/L in ambulatory CKD patients 1
• Benefits include: Increased serum albumin, decreased protein degradation, fewer hospitalizations 1

Acute Kidney Injury

In the prespecified subgroup of patients with AKIN score 2-3, bicarbonate therapy improved day 28 survival (54% vs 37%, p=0.0283) in the BICAR-ICU trial. 3

• Consider bicarbonate more strongly in patients with acute kidney injury and severe acidosis 3
• This represents the strongest evidence for benefit from the largest randomized trial 3

Common Pitfalls to Avoid

• Giving bicarbonate for pH ≥ 7.15 in sepsis/lactic acidosis (no benefit, potential harm) 1
• Administering bicarbonate without ensuring adequate ventilation (causes paradoxical intracellular acidosis) 1
• Mixing with calcium or catecholamines (causes precipitation or inactivation) 1
• Attempting complete pH normalization in first 24 hours (causes rebound alkalosis) 1, 2
• Using hypertonic 8.4% solution in newborns (must dilute to 4.2%) 1
• Ignoring potassium replacement (bicarbonate causes hypokalemia) 1
• Treating respiratory acidosis with bicarbonate (ventilation is the definitive treatment) 1