Pharmacology
Sodium bicarbonate is an alkalinizing agent. It increases plasma bicarbonate, buffers excess hydrogen ions, raises blood pH and reverses the clinical signs of acidemia. Sodium bicarbonate can alter the effect of certain drugs on sodium channels in cardiac tissue. Sodium bicarbonate dissociates to sodium and bicarbonate ions in water. Sodium is the principal cation of the extracellular fluid. Bicarbonate is found in body fluids and plasma. The normal plasma level of bicarbonate ranges from 22 to 28 mmol/L. Bicarbonate is a component of the principal extracellular buffer in the body, the bicarbonate-carbonic acid buffer. Bicarbonate buffers excess hydrogen ions by converting to carbonic acid or carbon dioxide and water. Plasma bicarbonate is regulated by the kidney. In a healthy adult with normal renal function, less than 1% of bicarbonate is excreted in the urine; most of the filtered bicarbonate ion is reabsorbed.
Indications
Oral: Sodium bicarbonate is given as a gastric, systemic and urinary alkalinizer. It can be used in conditions (e.g., chronic renal failure) requiring prolonged therapy with an alkalinizing agent.
Parenteral: Sodium bicarbonate iv is indicated for the treatment of metabolic acidosis which may occur in severe renal disease, uncontrolled diabetes (see Precautions), shock or severe dehydration, extracorporeal circulation of blood, cardiac arrest and severe lactic acidosis. The underlying cause of the acidemia should also be addressed.
Urine alkalinization in the treatment of drug overdose, to diminish nephrotoxicity of heme pigments and reduce the frequency of contrast medium-induced nephrotoxicity.
Drug overdose with agents that produce cardiotoxic effects involving sodium channel blockade.
Sodium bicarbonate is used in severe diarrhea when loss of bicarbonate has been significant and as an adjunct in the treatment of hyperkalemia.
Precautions
Sodium bicarbonate is physically and/or chemically incompatible with many drugs. Specialized references should be consulted for specific compatibility information.
Alkalinization of the urine can decrease the clearance of amphetamines, quinidine, pseudoephedrine and possibly other sympathomimetics. Urinary alkalinization can increase the clearance of chlorpropamide, lithium, salicylates and tetracyclines.
It is not known to what extent sodium bicarbonate distributes into breast milk.
It is not known whether sodium bicarbonate can cause fetal harm when administered during pregnancy.
Contraindications
Patients with: metabolic or respiratory alkalosis, hypocalcemia (because of an increased risk of alkalosis-induced tetany), excessive chloride loss from vomiting or from continuous gastrointestinal suction, states of hypoventilation or a risk of developing diuretic-induced hypochloremic alkalosis. Sodium bicarbonate should not be used as an antidote in the treatment of acute ingestion of strong acids.
Adverse Effects
Oral sodium bicarbonate may cause gastric distention and flatulence.
Extravasation of hypertonic solutions of sodium bicarbonate has been reported to cause chemical cellulitis resulting in tissue necrosis, ulceration, and/or sloughing at the site of injection.
Excessive parenteral doses may cause hypokalemia, accompanied by dry mouth, increased thirst, irregular heart beat, mood or mental changes, muscle cramps or pain, or weak pulse.
Administration of large doses or administration to patients with renal impairment may cause metabolic alkalosis which may be accompanied by hyperirritability or tetany.
Rapid alkalinization with sodium bicarbonate, in patients with ketoacidosis, may result in cerebral dysfunction, obtundation, seizures, and peripheral tissue hypoxia and lactic acidosis.
Hypernatremia, hyperosmolality and peripheral or pulmonary edema may occur when sodium bicarbonate is administered in large doses or in patients with renal insufficiency, heart failure or those predisposed to sodium retention and edema.
Overdose
Bicarbonate should be stopped and the patient managed according to the degree of alkalemia present. Sodium chloride 0.9% injection may be given iv. Potassium chloride may also be indicated if hypokalemia is present. Severe alkalemia may be accompanied by hyperirritability or tetany and these symptoms may be controlled by calcium gluconate. An acidifying agent such as ammonium chloride may also be indicated in severe alkalemia, except in patients with hepatic disease.
Dosage
To aid in converting: 84 mg of sodium bicarbonate = 1 mmol (1 mEq) of sodium bicarbonate = 1 mmol (1 mEq) each of sodium and bicarbonate ions. An 8.4% sodium bicarbonate solution = 84 mg/mL of sodium bicarbonate = 1 mmol (1 mEq)/mL of sodium bicarbonate.
Oral: Acidosis Associated with Chronic Renal Failure: Adults: Initial dose is 1.7 to 3 g daily in divided doses, with subsequent adjustment according to plasma bicarbonate concentration; fluid and electrolyte balance must be carefully monitored in these patients because of the potentially large sodium load associated with bicarbonate therapy.
Antacid: Adults: 325 mg to 2 g given 1 to 4 times daily for short term use.
Urinary Alkalinizer: Adults: 4 g initially, then 1 to 2 g every 4 hours. Some patients may require up to 16 g daily. Dosage should be titrated to maintain desired urinary pH.
Parenteral: Acidosis: Adults and Children Over 2 Years: The dosage of sodium bicarbonate can be based on the severity of the condition, laboratory values and the patient's weight.
Frequent evaluations of the patient are required during therapy to monitor acid-base and fluid and electrolyte balance. Full correction of acid-base balance should not be attempted during the first 24 hours because of the risk of delayed compensation and alkalosis. The initial dose is usually 2 to 5 mmol/kg administered as an iv infusion over 4 to 8 hours. Repeated dosage will be dependent on response to the initial dose and the clinical condition of the patient with respect to the cause of acidosis. Generally, the magnitude and frequency of subsequent doses should decrease once symptoms of severe acidosis have ameliorated.
Children ≤2 Years: The initial dose for infants and children under 2 years is usually 1 mmol/kg administered slowly in a concentration of 0.5 mmol/mL (see Precautions). Subsequent dosage will depend on the clinical status of the patient. A maximum daily dose of 8 mmol/kg has been recommended.
Cardiac Arrest: Sodium bicarbonate is not recommended for routine use during CPR. It is only used when clearly indicated and where adequate ventilation can be ensured (see Precautions).
Adults: An initial dose of 1 mmol/kg (1 mL of sodium bicarbonate 8.4% solution per kg body weight) may be given by rapid iv injection with repeated doses of 0.5 mmol/kg (0.5 mL/kg sodium bicarbonate 8.4%) every 10 minutes during continued cardiac arrest.
Children: An initial dose of 1 mmol/kg may be given slowly iv in a concentration of 1 mmol/mL (8.4% solution) to children 2 years of age and older. Subsequent doses of 1 mmol/kg may be considered at 10 minute intervals during continued cardiac arrest. Infants and children under 2 years may receive the above dosage, but a lower solution concentration is recommended (e.g., 0.5 mmol/mL or 4.2%).
Cardiotoxic Effects of Drug Overdose: An iv bolus of 1 to 2 mmol/kg over 1 to 2 minutes. This can be repeated as needed to maintain a blood pH of 7.45 to 7.55. Bolus dosing can be followed by a continuous infusion of sodium bicarbonate if required.
Contrast Medium-Induced Nephrotoxicity: Sodium bicarbonate can be administered to patients at risk for contrast medium-induced nephrotoxicity to help avoid this complication. In one suggested regimen add 150 mmol of sodium bicarbonate to 850 mL D5W. Administer at 3 mL/kg/h for 1 hour before contrast administration then 1 mL/kg/h for 6 hours after.
Urinary Alkalinization: In the presence of adequate urine output, urine alkalinization can be achieved by infusing 100 to 150 mmol sodium bicarbonate in 1 litre D5W at 150-200 mL/h. The infusion rate should be adjusted to a target urinary pH of 7.0 to 8.0.
