In addition to CPR, sodium bicarbonate is the treatment for cardiac arrest caused by which disorder?

• A. Hyperkalemia
• B. Cocaine overdose
• C. Tricyclic antidepressant overdose
• D. Hypoxia

Answer: (C)

When cardiac arrest is due to overdose of drugs that block cardiac fast sodium channels, sodium bicarbonate is used alongside CPR to reverse the blockade. Tricyclic antidepressants are classic examples of such agents. The overdose causes wide QRS complexes and poor conduction because the drug narrows the heart’s sodium channels. Administering sodium bicarbonate provides two helpful effects: a sodium load that helps overcome the channel blockade, and alkalinization of the blood that changes the drug’s ionization state, reducing its ability to bind to and block those channels in the myocardium. This combination improves intraventricular conduction and stabilizes the rhythm during resuscitation. Clinically, the goal is to raise the pH to about 7.45–7.55 and use a sodium bicarbonate bolus (and infusion as needed) to sustain that level. This approach isn’t the standard remedy for cardiac arrest caused by other issues like hyperkalemia, hypoxia, or stimulant overdoses, where different targeted treatments are used.