DESCRIPTION

Sodium bicarbonate is a medication used to alkalinize the blood or urine.

FORMS AND USES

Sodium bicarbonate injection USP (NaHCO₃) is available at concentrations of 2.5%, 5%, 7.5% (44 mEq/50 ml ampule) or 8.4% (50 mEq/50 ml ampule).

MECHANISM OF ACTION

• Serum alkalinization
  • NaHCO₃ bolus transiently increases serum sodium concentration and increases serum pH.
  • Increased plasma sodium concentration antagonizes sodium channel blockade induced by agents with type 1 antidysrhythmic activity.
• Urinary alkalinization
  • NaHCO₃ infusion is used to increase urinary pH above 7.5.
  • For weak acids (salicylate; phenobarbital; chlorpropamide; 2,4-dichlorophenoxy acetic acid), increased pH produces charged species in the urine; charged species are reabsorbed poorly and urinary excretion is increased.
• Inhalation of NaHCO₃ may neutralize acid.
  • This has been reported in uncontrolled studies to decrease pain and respiratory symptoms following chlorine inhalation.
  • The proposed mechanism of action is unclear.

DRUG AND DISEASE INTERACTIONS

• Sodium load may exacerbate conditions with fluid overload (e.g., congestive heart failure).
• Hypernatremia may result from repeated administration.

PREGNANCY AND LACTATION

US FDA Pregnancy Category C. Studies have shown animal teratogenic or embryocidal effects, but there are no controlled studies in women, or no studies are available in either animals or women.

Section Outline:

• DESCRIPTION
• FORMS AND USES
• MECHANISM OF ACTION
• DRUG AND DISEASE INTERACTIONS
• PREGNANCY AND LACTATION

• Tricyclic antidepressant drug toxicity
  • The purpose of NaHCO₃ administration is to narrow the QRS complex.
  • The use of NaHCO₃ is based on the ECG, and is recommended for patients with a QRS interval at or above 120 msec (0.12 seconds).
  • NaHCO₃ is not recommended for treatment of coma or hypotension alone because its efficacy is not well supported by current evidence.
• Type 1 antidysrhythmic drug toxicity
  • The purpose of NaHCO₃ administration is to narrow the QRS complex.
  • Case reports suggest that quinine, quinidine, encainide, and flecainide, as well as other drugs that block the sodium channel (e.g., propoxyphene, cocaine, diphenhydramine), respond to NaHCO₃.
  • Use is recommended for patients with a QRS interval at or above 120 msec (0.12 seconds).
• Salicylate poisoning
  • The purpose of administering NaHCO₃ is to produce urinary alkalinization.
  • Use is recommended for the patient with clinically significant salicylate poisoning (systemic symptoms or signs).
  • NaHCO₃ should be used with caution in cases of adult respiratory distress syndrome, renal failure, congestive heart failure, and states of volume overload.
• Phenobarbital poisoning
  • The purpose of administering NaHCO₃ is to produce urinary alkalinization.
  • Case reports and case series suggest that NaHCO₃ is helpful in increasing elimination, but they have not shown it to affect the course of illness; therefore, its use is not routinely recommended.
• Chlorpropamide toxicity
  • The purpose of administering NaHCO₃ is to produce urinary alkalinization.
  • Experimental evidence in normal volunteers suggests that NaHCO₃ increases excretion, but it has not been shown to affect the course of illness and is not routinely recommended.
• Chlorphenoxy herbicides (e.g., 2,4-dichlorophenoxyacetic acid) poisoning
  • The purpose of administering NaHCO₃ is to produce urinary alkalinization.
  • It has been recommended in symptomatic patients; however, adequate data are lacking and its use is not routinely recommended.
• Chlorine gas poisoning
  • The purpose of having a patient inhale NaHCO₃ is to neutralize acid.
  • Case reports and case series suggest that NaHCO₃ is helpful, but contradictory evidence exists and indications have not been established.
  • The use of inhaled NaHCO₃ in the case of chlorine gas poisoning is questionable, but it has not been harmful.
• Lactic acidosis induced by a poison
  • NaHCO₃ has been used for the patient with metabolic acidosis that cannot be promptly treated by another means.
  • The use of NaHCO₃ for treatment of lactic acidosis is not recommended because it is not well supported by current experimental evidence.
• Rhabdomyolysis induced by a poison
  • NaHCO₃ for treatment of rhabdomyolysis is recommended by some clinicians, but it is not well supported by experimental evidence and therefore is not recommended.
  • Appropriate rehydration to maintain urine output at 1 to 2 ml/kg per hour by use of isotonic saline infusion should be the goal of therapy.

CONTRAINDICATIONS

• Relative contraindications. Preexisting volume overload syndrome (congestive heart failure, renal failure, etc.)
• Absolute contraindications. Serum pH above 7.55 (for serum alkalinization)

ADVERSE EFFECTS

• Paradoxical intracellular acidosis may develop in patients with lactic acidosis or diabetic ketoacidosis.
• Electrolyte abnormalities: Hypernatremia, hypokalemia, hypochloremia, hypocalcemia, or alkalosis may occur.
• Fluid overload may worsen congestive heart failure or other volume overload states.

Section Outline:

• CONTRAINDICATIONS
• ADVERSE EFFECTS

TRICYCLIC ANTIDEPRESSANT DRUG TOXICITY

• Adult. Initial administration of NaHCO₃ should be one to two ampules (either 44 or 50 mEq) intravenous push; if the QRS duration does not narrow to less than 100 msec, dose should be repeated until arterial blood pH reaches 7.45 to 7.55.
• Pediatric. A dose of 1 to 2 mEq/kg intravenous push should be administered; if the QRS duration does not narrow to less than 100 msec, dose should be repeated until arterial blood pH reaches 7.45 to 7.55.
• Continuous intravenous infusion should not be initiated.

TYPE 1 ANTIDYSRHYTHMIC DRUG TOXICITY

• NaHCO₃ may be useful against quinine, quinidine, encainide, flecainide, propoxyphene, and diphenhydramine.
• The dose is unknown, but generally considered to be the same as for tricyclic antidepressant drugs.

SALICYLATE POISONING

• Adult
  • NaHCO₃ should be administered as one to two ampules (either 44 or 50 mEq) intravenous push.
  • In addition, three ampules of NaHCO₃ (either 44 or 50 mEq) should be mixed in 1 L D5W and infused at 200 ml/h.
  • Urinary pH should be checked frequently; the rate of infusion can be increased within clinically reasonable boundaries (consider underlying medical conditions) to produce a urinary pH of 7.5 or greater.
• Pediatric
  • One to two mEq/kg should be administered via intravenous push.
  • In addition, one or two ampules (either 44 or 50 mEq) of NaHCO₃ should be mixed in 1 L D5W and infused at a rate within clinically reasonable boundaries (consider underlying medical conditions) to produce a urinary pH of 7.5 or above.
  • Supplemental potassium administration should be considered.

PHENOBARBITAL, CHLORPROPAMIDE, OR CHLORPHENOXY HERBICIDE POISONING

• The use of NaHCO₃ is not routinely recommended.
• Adult
  • NaHCO₃ should be administered as one to two ampules (either 44 or 50 mEq) intravenous push.
  • Three ampules of NaHCO₃ should be mixed in 1 L D5W and infused at 200 ml/h.
  • Urinary pH should be monitored frequently; the rate should be increased within clinically reasonable boundaries (considering underlying medical conditions) to produce a urinary pH of 7.5 or above.
• Pediatric
  • One to two mEq/kg should be administered via intravenous push.
  • One or two ampules (either 44 or 50 mEq) of NaHCO₃ should be mixed in 1 L D5W and infused at a rate within clinically reasonable boundaries (considering underlying medical conditions) to produce a urinary pH of 7.5 or above.
• Supplemental potassium administration should be considered.

CHLORINE GAS POISONING

• Adult or pediatric patients: Two cc NaHCO₃ (7.5% or 8.4%) should be mixed with 2 cc 0.9% normal saline USP.
• This NaHCO₃ inhalant should be administered to the patient by hand-held nebulizer.

METABOLIC ACIDOSIS INDUCED BY A POISON

• The use of NaHCO₃ is not routinely recommended.
• The most important treatment is to reverse the underlying cause of acidosis.

RHABDOMYOLYSIS INDUCED BY A POISON

The use of NaHCO₃ is not routinely recommended.

Section Outline:

• TRICYCLIC ANTIDEPRESSANT DRUG TOXICITY
• TYPE 1 ANTIDYSRHYTHMIC DRUG TOXICITY
• SALICYLATE POISONING
• PHENOBARBITAL, CHLORPROPAMIDE, OR CHLORPHENOXY HERBICIDE POISONING
• CHLORINE GAS POISONING
• METABOLIC ACIDOSIS INDUCED BY A POISON
• RHABDOMYOLYSIS INDUCED BY A POISON

• Poorly monitored infusion of maintenance NaHCO₃ may become excessive, producing a systemic pH above 7.6, which impairs cardiac contractility.
• Hypernatremia and fluid overload may occur.
• Pediatric patients
  • Rapid administration of large amounts of NaHCO₃ to children under the age of 2 years has been associated with hypernatremia, decreased cerebrospinal fluid pressure, and intracranial hemorrhage.
  • Use of the 4.2% solution (1:1 dilution of 8.4% solution) may be preferable.
• Geriatric patients may be susceptible to sodium and fluid overload.

RECOMMENDED READING

Stackpoole P. Lactic acidosis: the case against bicarbonate therapy. Ann Intern Med 1986;105:276-279.

Wax PM, Hoffman RS. Sodium bicarbonate. In: Hoffman RS, Goldfrank LR, eds. Critical care toxicology. New York: Churchill Livingstone, 1991:81-108.

Author: Richard C. Dart

Reviewer: Katherine M. Hurlbut