In an adult with severe metabolic acidosis (arterial pH < 7.10) causing hemodynamic instability, impaired myocardial contractility, or life‑threatening hyperkalemia, when should sodium bicarbonate be administered, what dose should be used, and how should it be monitored?

Sodium Bicarbonate in Severe Metabolic Acidosis

Administer sodium bicarbonate 50 mmol (50 mL of 8.4% solution) IV slowly when arterial pH < 7.1 with base excess < -10, or in specific emergencies including life-threatening hyperkalemia, tricyclic antidepressant overdose with QRS widening, or hemodynamic instability unresponsive to vasopressors. 1, 2, 3

Primary Indications for Sodium Bicarbonate

Severe metabolic acidosis requires three criteria before bicarbonate administration:

• Arterial pH < 7.1 AND base excess < -10 4, 1, 2
• Effective ventilation already established or immediately achievable 4, 1
• Underlying cause being actively treated (bicarbonate buys time but does not treat disease) 4, 1

Special clinical scenarios where bicarbonate is indicated regardless of pH threshold:

• Life-threatening hyperkalemia (as temporizing measure while definitive therapy initiated) 1, 3
• Tricyclic antidepressant or sodium channel blocker overdose with QRS > 120 ms: give 50-150 mEq bolus of hypertonic solution (1000 mEq/L), target pH 7.45-7.55 1, 3
• Cardiac arrest after first epinephrine dose fails with documented severe acidosis 1, 3
• Hemodynamic instability with vasopressor dependency and pH < 7.1 2, 5

Absolute Contraindications

Do NOT give bicarbonate in these situations:

• Hypoperfusion-induced lactic acidemia with pH ≥ 7.15 (two blinded RCTs showed no benefit, potential harm including increased lactate, sodium/fluid overload, increased PaCO2, decreased ionized calcium) 4, 1
• Sepsis-related acidosis with pH ≥ 7.15 4, 1
• Diabetic ketoacidosis with pH ≥ 7.0 1, 2
• Respiratory acidosis without adequate ventilation established 4, 1

Dosing Protocol

Initial dose:

• Adults: 50 mmol (50 mL of 8.4% solution) IV given slowly over several minutes 2, 3, 6
• Alternative: 1-2 mEq/kg (44.6-100 mEq) for cardiac arrest as rapid bolus 3, 6
• Pediatric: 1-2 mEq/kg IV slowly; use 0.5 mEq/mL (4.2%) concentration for children < 2 years (dilute 8.4% solution 1:1 with normal saline) 1, 3

Continuous infusion (if ongoing alkalinization needed):

• Prepare 150 mEq/L solution 1, 3
• Infuse at 1-3 mL/kg/hour 1, 3
• For DKA with pH < 6.9: 100 mmol in 400 mL sterile water at 200 mL/hour 1
• For DKA with pH 6.9-7.0: 50 mmol in 200 mL sterile water at 200 mL/hour 1

Repeat dosing:

• Guided by arterial blood gas analysis every 2-4 hours, NOT empirically 1, 3
• In cardiac arrest: may repeat 50 mL (44.6-50 mEq) every 5-10 minutes based on pH monitoring 6

Critical Pre-Administration Requirements

Before EVERY dose, ensure:

1. Mechanical ventilation or adequate spontaneous ventilation to eliminate CO2 (bicarbonate generates CO2 that causes paradoxical intracellular acidosis if not cleared) 4, 1, 7
2. Target minute ventilation to achieve PaCO2 30-35 mmHg for synergistic alkalinization 1
3. Separate IV line from calcium-containing solutions and vasoactive amines (causes precipitation/inactivation) 4, 1, 3
4. Flush IV line with normal saline before and after bicarbonate 1

Monitoring Requirements

Every 2-4 hours during active therapy: 1, 3

• Arterial blood gases (pH, PaCO2, bicarbonate)
• Serum sodium (stop if > 150-155 mEq/L)
• Serum potassium (bicarbonate shifts K+ intracellularly; replace as needed)
• Ionized calcium (large doses decrease iCa2+, impairing cardiac contractility)

Target endpoints:

• pH 7.2-7.3, NOT complete normalization 1, 3, 8
• Avoid pH > 7.50-7.55 (causes hypokalemia, impaired oxygen delivery) 1, 3
• Hemodynamic stability achieved 2
• Resolution of QRS prolongation in toxicity cases 1, 3

Common Pitfalls and How to Avoid Them

Paradoxical intracellular acidosis: Bicarbonate generates CO2 that crosses cell membranes faster than bicarbonate, worsening intracellular pH if ventilation inadequate. Always establish effective ventilation BEFORE giving bicarbonate. 4, 1, 7

Hypokalemia: Alkalinization drives potassium intracellularly. Monitor K+ every 2-4 hours and replace aggressively, especially in DKA where total body potassium already depleted. 1

Hypocalcemia: Large doses (> 50-100 mEq) decrease ionized calcium, worsening cardiac contractility. Monitor iCa2+ and replace if symptomatic or significantly decreased. 1, 7

Hypernatremia and fluid overload: Each 50 mL of 8.4% solution contains 44.6 mEq sodium. In oliguric patients or those with renal failure, consider using 4.2% concentration (dilute 8.4% solution 1:1 with sterile water) to reduce sodium load. 1, 7

Overshoot alkalosis: Attempting full correction in first 24 hours causes alkalosis due to delayed ventilatory readjustment. Target pH 7.2-7.3 initially, allow kidneys to complete correction over subsequent days. 6, 8

Increased lactate production: Bicarbonate paradoxically increases lactate in some patients with lactic acidosis. This is why it should NOT be used for pH ≥ 7.15 in hypoperfusion states. 4, 1

Special Populations

Diabetic ketoacidosis:

• Only give if pH < 6.9 after initial hour of hydration 1, 2
• Ketones convert back to bicarbonate once insulin given; exogenous bicarbonate usually unnecessary 8

Chronic kidney disease:

• Oral sodium bicarbonate 2-4 g/day (25-50 mEq/day) for maintenance, target serum bicarbonate ≥ 22 mmol/L 1
• IV bicarbonate in acute setting increases risk of fluid overload in oliguric patients 1

Cardiac arrest:

• Give 1 mmol/kg (1 mEq/kg) as single bolus AFTER first epinephrine dose ineffective 1
• NOT recommended routinely (does not improve hospital admission or discharge rates) 4, 1

When to Stop Bicarbonate

Discontinue when: 1, 3

• pH reaches 7.2-7.3
• Hemodynamic stability achieved
• Serum sodium > 150-155 mEq/L
• pH > 7.50-7.55
• Severe hypokalemia develops
• Underlying cause corrected (e.g., spontaneous circulation restored, ketoacidosis resolving)

Alternative Approaches

Renal replacement therapy with bicarbonate-buffered dialysate is preferred over IV bicarbonate for severe, refractory lactic acidosis in patients with acute kidney injury, as it removes lactate while providing bicarbonate without causing hypervolemia or hypernatremia. 1