BICARBONATESODIUM

Abrar SalehMai Mahfouz

Pharmacology

•Sodium bicarbonate is a buffering agent that reacts with hydrogen ions to correct acidemia and produce alkalemia

• Urinary alkalinization from renally excreted bicarbonate ions enhances the renal elimination of certain acidic drugs (eg, salicylate, chlorpropamide, chlorophenoxy herbicides, fluoride, and phenobarbital) and helps prevent renal tubular damage from deposition of myoglobin in patients with rhabdomyolysis

• It prevents precipitation (by enhancing solubility) of methotrexate with high-dose therapy.

• prevent intracellular distribution of salicylate and formate (a toxic metabolite of methanol).

• The sodium ion load and alkalemia produced by hypertonic sodium bicarbonate reverse the sodium channel-dependent membrane-depressant effects of several drugs (eg,tricyclic antidepressants, type Ia and type Ic antiarrhythmic agents, propranolol, propoxyphene, cocaine, and diphenhydramine).

• Alkalinization causes an intracellular shift of potassium and is used for the acute treatment of hyperkalemia.

• Sodium bicarbonate given orally or by gastric lavage forms an insoluble salt with iron and theoretically may help prevent absorption of ingested iron tablets (unproved).

Indications• Severe metabolic acidosis resulting from intoxication (eg

methanol, ethylene glycol, or salicylates )or from excessive lactic acid production (status epilepticus or shock).

• To produce urinary alkalinization enhance elimination of certain acidic drugs

(salicylate,phenobarbital, chlorpropamide, chlorophenoxy herbicides-2,4-D)

prevent nephrotoxicity from the renal deposition of myoglobin or precipitation of methotrexate.

Also for internal contamination of uranium from radiation emergencies to prevent acute tubular necrosis

• Cardiotoxicity with impaired ventricular depolarization (as evidenced by a prolonged QRS interval) caused by tricyclic antidepressants, type Ia or type Ic antiarrhythmics

Contraindications

A. Significant metabolic or respiratory alkalemia or hypernatremia

B. Severe pulmonary edema associated with volume overload

C. Intolerance to sodium load (renal failure, CHF)

Adverse effects

A. Excessive alkalemia: impaired oxygen release from hemoglobin, hypocalcemic tetany, and paradoxic intracellular acidosis (from elevated pCO2 concentrations) and hypokalemia

B. Hypernatremia and hyperosmolality

C. Aggravation of CHF and pulmonary edema

D. Extravasation leading to tissue inflammation and necrosis (product is hypertonic)

E. May exacerbate QT prolongation and associated dysrhythmias (eg, torsade de pointes) as a result of electrolyte shifts (hypokalemia)

Adverse effects

Pregnancy

Category

C

Drug or laboratory interactions

Do not mix with other parenteral drugs because of the possibility of drug inactivation or precipitation

Dosage and method of administration (adults and children)

A. Metabolic acidemia• (0.5-1 mEq/kg) IV bolus → repeat to correct serum pH 7.2• Salicylates, methanol, or ethylene glycol pH 7.4-7.5

B. Urinary alkalinization• 44-100 mEq in 1 L of 5% dextrose in 0.25% normal saline or 88-150 mEq in 1 L of 5% dextrose at 2-3 mL/kg/h (adults 150-200 mL/h)• Maintain urine pH 7-8.5

C. Cardiotoxic drug intoxication• (1-2 mEq/kg) IV bolus over 1-2 minutes → repeat as needed to improve cardiotoxic manifestations (eg, prolonged QRS interval, wide-complex tachycardia, hypotension) and maintain serum pH 7.45-7.55

• There is no evidence that constant infusions are as effective as boluses given as needed

Dosage and method of administration (adults and children)

Formulations

Several products are available• 4.2% (0.5 mEq/mL preferred for neonates and young children)• 7.5% (0.89 mEq/mL) • 8.4% (1 mEq/mL)

Volumes of 10-500 mL

The most commonly used formulation available in most emergency is 8.4% ("hypertonic") sodium bicarbonate in 50-mL ampules or prefilled syringes

The suggested minimum stocking level to treat a

70-kg adult for the first 24 hours is 10 ampules

or syringes (approximately 500 mEq)