Sodium bicarbonate is used with CPR for cardiac arrest caused by overdose of which class of antidepressants?

• A. SSRI
• B. MAOI
• C. Tri-cyclic antidepressants
• D. SNRI

Answer: (C)

Sodium bicarbonate is used in CPR for cardiac arrest due to overdose of a class of antidepressants because these drugs cause dangerous sodium channel blockade in the heart. Tricyclic antidepressants block fast sodium channels in the myocardium, leading to slowed conduction, widened QRS, and potentially lethal arrhythmias. Giving bicarbonate helps in two ways: it provides a sodium load to overcome the blockage and it alkalinizes the serum. The higher pH reduces the amount of uncharged drug that penetrates cardiac tissue, decreasing its interaction with sodium channels, while the extra sodium helps the heart conduct more effectively despite the blockade. Clinically, this is started as an IV bolus of sodium bicarbonate and guided to maintain a target pH around 7.45–7.55, with careful monitoring of electrolytes and acid-base status. This approach is specifically advantageous for tricyclic antidepressant overdose, whereas overdoses of other antidepressants like SSRIs, MAOIs, or SNRIs do not produce the same pattern of sodium-channel–mediated cardiac toxicity that responds to bicarbonate therapy.