What is the correct preparation of D5 (5% dextrose) with 8.4% sodium bicarbonate (NaHCO3) for forced alkaline diuresis in a patient with toxic ingestion and adequate renal function?

Preparation of D5 with Sodium Bicarbonate for Forced Alkaline Diuresis

Standard Preparation Protocol

For forced alkaline diuresis (urinary alkalinization), add 100-150 mEq of sodium bicarbonate to 1 liter of D5W (5% dextrose in water) to create an isotonic bicarbonate solution. 1

Step-by-Step Mixing Instructions

• Start with 1000 mL of D5W as the base solution 1
• Add 100-150 mEq of sodium bicarbonate (using 8.4% solution, this equals approximately 119-178 mL of 8.4% NaHCO3) 1
• The resulting solution will have a sodium bicarbonate concentration of approximately 150 mEq/L 1
• This creates an isotonic solution suitable for continuous infusion without causing hyperosmolar complications 1

Infusion Rate Guidelines

• Administer at 1-3 mL/kg/hour to maintain urinary alkalinization 1
• Target urine pH ≥7.5 to maximize renal excretion of weak acids like salicylates 2, 3
• Monitor urine pH hourly during active alkalinization 3

Clinical Context: When This Preparation Is Indicated

Forced alkaline diuresis is first-line treatment for moderately severe salicylate poisoning in patients who do not meet criteria for hemodialysis. 2, 3

Specific Indications for Urinary Alkalinization

• Salicylate poisoning with plasma concentrations 3.6-7.2 mmol/L (50-100 mg/dL) without severe toxicity 2
• 2,4-dichlorophenoxyacetic acid poisoning (requires both alkalinization AND high urine flow ~600 mL/h) 3
• Mecoprop poisoning (requires both alkalinization AND high urine flow) 3
• Methotrexate toxicity (limited evidence but clinically employed) 3

When NOT to Use This Preparation

• Do NOT use for sodium channel blocker/tricyclic antidepressant toxicity—these require hypertonic sodium bicarbonate boluses (1000 mEq/L), not continuous alkaline diuresis 1, 4, 5
• Do NOT use for metabolic acidosis correction—this requires different concentrations and monitoring 1
• Avoid in patients with fluid overload, pulmonary edema, or severe renal impairment 2, 3

Critical Monitoring Requirements

Electrolyte Management

• Hypokalemia is the most common complication of urinary alkalinization and must be aggressively corrected. 3
• Add 20-40 mEq KCl per liter of the D5/bicarbonate solution to prevent hypokalemia 3
• Monitor serum potassium every 2-4 hours and maintain >3.5 mEq/L 1, 3
• Alkalemia shifts potassium intracellularly, so supplementation is nearly always required 1

pH Monitoring

• Check arterial or venous blood gases every 2-4 hours 1
• Target serum pH 7.45-7.55 (mild alkalemia enhances urinary alkalinization) 3
• Avoid serum pH >7.70 as this increases risk of alkalotic tetany 3
• Monitor urine pH hourly with goal ≥7.5 for optimal weak acid excretion 2, 3

Sodium and Fluid Balance

• Monitor serum sodium every 2-4 hours to prevent hypernatremia 1
• Target serum sodium <150-155 mEq/L 1
• Watch for fluid overload, especially in patients with cardiac or renal disease 1, 3

Important Safety Considerations

Contraindications and Precautions

• Never mix sodium bicarbonate with calcium-containing solutions in the same IV line—precipitation will occur. 1, 6
• Do not mix with vasoactive amines (epinephrine, norepinephrine, dopamine) as bicarbonate inactivates catecholamines 1, 6
• Flush IV line with normal saline before and after bicarbonate administration if other medications are being given 1
• Ensure adequate ventilation before starting bicarbonate therapy, as CO2 production increases and requires pulmonary elimination 1, 3

Common Pitfalls to Avoid

• Do not confuse urinary alkalinization (150 mEq/L in D5W) with hypertonic bicarbonate boluses (1000 mEq/L) used for sodium channel blocker toxicity—these are completely different indications and preparations 1, 5
• Do not use forced diuresis alone without alkalinization for salicylate poisoning—urine pH is far more important than urine flow rate for salicylate excretion 3, 7
• Avoid using lactated Ringer's or other calcium-containing solutions as the base instead of D5W 6
• Do not delay hemodialysis in severely poisoned patients (altered mental status, pulmonary edema, renal failure, salicylate >7.2 mmol/L) by attempting urinary alkalinization 2

Alternative Preparation Method

• Some protocols use 3 ampules (150 mEq) of sodium bicarbonate in 1 liter of D5W 1
• This creates a slightly more concentrated solution but remains isotonic and safe for continuous infusion 1
• The key principle is maintaining isotonicity (approximately 150 mEq/L) rather than using hypertonic preparations 1