What are the contraindications for intravenous sodium bicarbonate infusion in metabolic acidosis?

Contraindications for Bicarbonate Infusion in Acidosis

Sodium bicarbonate is absolutely contraindicated in patients losing chloride through vomiting or continuous gastrointestinal suction, and in those receiving diuretics that produce hypochloremic alkalosis. 1

Absolute Contraindications

Chloride-Losing States

• Patients with ongoing vomiting or continuous nasogastric suction should never receive bicarbonate, as this creates or worsens hypochloremic metabolic alkalosis 1
• Patients on loop or thiazide diuretics producing hypochloremic alkalosis are contraindicated from receiving bicarbonate 1

Inadequate Ventilation

• Bicarbonate is contraindicated when effective ventilation cannot be established, because it generates CO₂ that must be eliminated to prevent paradoxical intracellular acidosis 2, 3
• In respiratory acidosis or mixed acidosis with elevated PaCO₂, bicarbonate worsens hypercapnia and intracellular acidosis; THAM is preferred in these situations 4
• Patients on BiPAP with pure respiratory acidosis should never receive bicarbonate, as the CO₂ produced rapidly diffuses into cells causing paradoxical intracellular acidosis even if serum pH transiently rises 5

Specific pH Thresholds

• Hypoperfusion-induced lactic acidemia with pH ≥7.15 is a contraindication based on two blinded RCTs showing no hemodynamic benefit and demonstrable harm (sodium/fluid overload, increased lactate, elevated PaCO₂, decreased ionized calcium) 3
• Sepsis-related metabolic acidosis with pH ≥7.15 should not be treated with bicarbonate, as strong evidence demonstrates lack of benefit and potential adverse effects 3

Relative Contraindications Requiring Extreme Caution

Cardiac Arrest

• Routine bicarbonate administration during cardiac arrest is contraindicated (Class III recommendation), as it does not improve survival to hospital admission or discharge 2, 3
• Consider only after first epinephrine dose fails AND documented pH <7.1, or in specific toxidromes (hyperkalemia, TCA/sodium channel blocker overdose) 3

Diabetic Ketoacidosis

• Bicarbonate is not indicated for DKA when pH ≥7.0, as insulin therapy alone resolves the acidosis 3
• Only consider for DKA with pH <6.9 3

Hypernatremia and Volume Overload

• Patients with pre-existing hypernatremia should receive THAM instead of bicarbonate, as bicarbonate increases serum sodium while THAM decreases it 4
• Severe volume overload or heart failure represents a relative contraindication due to the large sodium load (each 50 mEq bicarbonate delivers 50 mEq sodium) 3

Hypokalemia

• Pre-existing hypokalemia is a relative contraindication, as bicarbonate shifts potassium intracellularly and can precipitate life-threatening hypokalemia 2, 3
• Potassium must be repleted before or concurrent with bicarbonate administration 3

Clinical Decision Algorithm

Step 1: Identify the type of acidosis

• If respiratory acidosis (elevated PaCO₂, normal/near-normal bicarbonate) → Do not give bicarbonate; optimize ventilation 5
• If metabolic acidosis → proceed to Step 2

Step 2: Check arterial pH

• If pH ≥7.15 in lactic acidosis or sepsis → Do not give bicarbonate (strong evidence of no benefit and potential harm) 3
• If pH 7.1–7.15 → Consider only after optimizing circulation, ventilation, and treating underlying cause 3
• If pH <7.1 → Proceed to Step 3

Step 3: Verify adequate ventilation

• Can the patient eliminate CO₂ (spontaneous adequate ventilation or mechanical ventilation with minute ventilation sufficient for PaCO₂ 30–35 mmHg)? 3
• If NO → Do not give bicarbonate; establish ventilation first 2, 3
• If YES → Proceed to Step 4

Step 4: Check for absolute contraindications

• Active vomiting or NG suction? → Do not give bicarbonate 1
• On loop/thiazide diuretics with hypochloremic alkalosis? → Do not give bicarbonate 1
• Hypernatremia (Na >150 mEq/L)? → Consider THAM instead 4
• If none present → Bicarbonate may be administered with close monitoring

Common Pitfalls to Avoid

• Never administer bicarbonate to "buy time" in septic shock with pH ≥7.15—two RCTs prove this causes harm without benefit 3
• Never give bicarbonate before ensuring mechanical or adequate spontaneous ventilation—this creates paradoxical intracellular acidosis that worsens outcomes 2, 3, 5
• Never use bicarbonate routinely in cardiac arrest—it does not improve survival and may worsen outcomes 2, 3
• Never mix bicarbonate with calcium-containing solutions or vasoactive amines (epinephrine, norepinephrine, dobutamine) in the same IV line—precipitation or inactivation will occur 3
• Never ignore pre-existing hypokalemia—bicarbonate will worsen it and precipitate arrhythmias; repleting potassium first is mandatory 3

Monitoring Requirements When Bicarbonate Is Given

• Arterial blood gases every 2–4 hours to assess pH, PaCO₂, and bicarbonate response 3
• Serum electrolytes every 2–4 hours: sodium (stop if >150–155 mEq/L), potassium (replace aggressively), ionized calcium (replace if symptomatic) 3
• Target pH 7.2–7.3, not complete normalization—avoid pH >7.50–7.55 3
• Ensure minute ventilation is adequate to eliminate the CO₂ generated by bicarbonate metabolism 3