What is the recommended dose of sodium bicarbonate (NaHCO3) for a 45 kg individual with an aspirin (acetylsalicylic acid) overdose?

Sodium Bicarbonate Dosing for Aspirin Overdose in a 45 kg Patient

For this 45 kg patient with aspirin overdose, administer an initial dose of 45-90 mEq (1-2 mEq/kg) of sodium bicarbonate intravenously, given slowly, followed by continuous infusion to maintain urinary alkalinization with a target urine pH of 7.5-8.0. 1, 2, 3

Initial Bolus Dosing

• Give 1-2 mEq/kg IV as the initial dose, which translates to 45-90 mEq for this 45 kg patient 1, 2, 3
• Administer this dose slowly over several minutes to avoid rapid osmolar shifts 3
• Use the 8.4% solution (1 mEq/mL), which means 45-90 mL of standard sodium bicarbonate solution 3

Continuous Infusion Protocol

• After the initial bolus, start a continuous infusion of 150 mEq/L sodium bicarbonate solution at 1-3 mL/kg/hour (45-135 mL/hour for this patient) to maintain urinary alkalinization 1
• The primary goal is urinary alkalinization (urine pH 7.5-8.0), not just serum alkalinization, as salicylate excretion depends much more on urine pH than urine flow rate 4
• Urinary alkalinization alone is at least as effective and possibly more effective than forced alkaline diuresis in enhancing salicylate removal 4

Critical Pre-Treatment Requirements

Before administering any sodium bicarbonate, ensure:

• Adequate ventilation is established, as bicarbonate produces CO2 that must be eliminated to prevent paradoxical intracellular acidosis 1, 2
• Serum potassium is approximately 4 mmol/L or higher - hypokalemia prevents effective urinary alkalinization and must be corrected first 1, 5
• The patient is euvolemic, as aspirin causes sodium and fluid retention 5, 4

Monitoring Requirements

Monitor every 2-4 hours:

• Arterial blood gases (pH, PaCO2, bicarbonate) 1, 2
• Serum electrolytes, particularly potassium and sodium 1, 2
• Urine pH (target 7.5-8.0) 4
• Salicylate concentrations 5, 6
• Serum sodium should not exceed 150-155 mEq/L 1, 7
• Serum pH should not exceed 7.50-7.55 1

Dosing Adjustments and Duration

• Continue bicarbonate infusion until salicylate concentrations are declining and in the non-toxic range 5, 6
• Repeat bolus doses of 1-2 mEq/kg may be given if acidosis persists, guided by arterial blood gas analysis 3
• The apparent elimination half-life of salicylate decreases from approximately 13.4 hours to 9.3 hours with bicarbonate therapy 6
• In patients with impaired renal function (which may be relevant given aspirin's effects), urinary alkalinization remains the mainstay of treatment 5

Critical Safety Considerations

Avoid these common pitfalls:

• Do not attempt forced diuresis - urinary alkalinization alone is safer and equally effective, as forced diuresis causes fluid retention and biochemical disturbances without additional benefit 4
• Do not mix sodium bicarbonate with calcium-containing solutions or vasoactive amines, as it inactivates catecholamines 1, 2
• Do not give bicarbonate without correcting hypokalemia first - a plasma potassium of approximately 4 mmol/L is needed for adequate urinary alkalinization 5
• Do not exceed 6 mmol/kg total dose (270 mEq for this patient), as this risks hypernatremia, fluid overload, metabolic alkalosis, and cerebral edema 8

Adjunctive Therapy

• Administer activated charcoal if the patient presents within 1-2 hours of ingestion and there is no aspiration risk - this decreases the median peak salicylate concentration by approximately 9.4 mg/L per gram of aspirin ingested 6
• Ensure adequate hydration to achieve euvolemia, but avoid aggressive fluid loading 5, 4

Special Considerations for This Patient

The 45 kg weight suggests either a pediatric patient or a small adult. The dosing remains 1-2 mEq/kg regardless, but for pediatric patients, ensure the concentration used is appropriate - children ≥2 years can receive 8.4% solution, but younger children require dilution to 4.2% 1. The evidence strongly supports that urinary alkalinization is the key therapeutic intervention, not the volume of fluid administered 4.