From the Guidelines
Sodium bicarbonate is recommended for treating tricyclic antidepressant (TCA) overdose when there are signs of cardiac toxicity, particularly QRS prolongation, ventricular dysrhythmias, or hypotension. The initial dose is 1-2 mEq/kg IV bolus, as supported by the 2023 American Heart Association guidelines 1. This treatment directly addresses the pathophysiology of TCA toxicity, which primarily affects cardiac sodium channels, leading to delayed cardiac conduction and potential arrhythmias.
Mechanism of Action
Bicarb therapy works through two mechanisms: it increases extracellular pH, which reduces the active form of the drug and decreases binding to sodium channels; and it provides sodium load, which overcomes the sodium channel blockade caused by TCAs. The combination of sodium loading and increasing the serum pH has an additive effect, as stated in the 2023 American Heart Association focused update 1.
Administration and Monitoring
The goal is to achieve and maintain a serum pH of 7.50-7.55, while avoiding extremes of hypernatremia (serum sodium not to exceed 150–155 mEq/L) and alkalemia (serum pH not to exceed 7.50–7.55) to avoid iatrogenic harm 1. Bicarb therapy should be continued until QRS duration normalizes and cardiac stability is achieved, with close monitoring of serum pH, electrolytes, and cardiac rhythm throughout treatment.
Key Considerations
- Experts recommend avoiding extremes of hypernatremia and alkalemia to avoid iatrogenic harm 1.
- If necessary, serum sodium can be increased separately by administration of hypertonic saline, and pH can be controlled by adjusting minute ventilation in intubated patients 1.
- Because hypertonic sodium bicarbonate therapy can cause hypokalemia, patients should be monitored and treated for hypokalemia during alkalemia therapy 1.
The 2023 American Heart Association guidelines provide the most recent and highest quality evidence for the use of sodium bicarbonate in TCA overdose, and therefore, its recommendations should be followed 1.
From the FDA Drug Label
Sodium bicarbonate is further indicated in the treatment of certain drug intoxications, including barbiturates (where dissociation of the barbiturate-protein complex is desired), in poisoning by salicylates or methyl alcohol and in hemolytic reactions requiring alkalinization of the urine to diminish nephrotoxicity of hemoglobin and its breakdown products The FDA drug label does not answer the question.
From the Research
Bicarb in TCA Overdose
- The use of sodium bicarbonate in tricyclic antidepressant (TCA) overdose is supported by several studies 2, 3, 4, 5
- Sodium bicarbonate is used to alkalinize the blood to a pH of 7.5, which can help reduce cardiotoxicity and improve cardiac arrhythmias 2, 4
- The administration of sodium bicarbonate can resolve arrhythmias even in the absence of acidosis, and it is recommended to use it before conventional antiarrhythmic drugs 4
- In cases of severe TCA toxicity, sodium bicarbonate may be beneficial in reducing QRS prolongation, reversing hypotension, and improving mental status 3, 4
- The dosage of sodium bicarbonate varies, but a common recommendation is to administer 1-2 mEq/kg 3, although some cases may require higher doses, such as 2650 mEq 3
- Sodium bicarbonate should be administered in conjunction with other treatments, such as fluid replacement, cardiac monitoring, and supportive therapy 2, 4, 6
- The use of sodium bicarbonate in TCA overdose is generally recommended, but the specific indications and dosing recommendations may vary depending on the individual case and the presence of other symptoms or conditions 4, 6