Which intravenous fluid is used for tricyclic antidepressant toxicity?

• A. Sodium bicarbonate
• B. Lactated Ringer's solution
• C. Normal saline
• D. 5% dextrose in water

Answer: (A)

Sodium bicarbonate is the intravenous fluid of choice for tricyclic antidepressant (TCA) toxicity primarily because it helps to reverse the toxic effects of the drugs by alkalizing the serum and the urine. TCAs can cause cardiovascular issues such as cardiac arrhythmias and hypotension, often due to sodium channel blockade. Administering sodium bicarbonate increases the blood pH and helps to stabilize cardiac membranes, reducing the risk of arrhythmias. Additionally, alkalinizing urine can enhance the elimination of TCAs from the body, facilitating their excretion and lowering the overall toxic burden.

In contrast, other intravenous fluids such as Lactated Ringer's solution, normal saline, and 5% dextrose in water do not provide the same therapeutic effects that sodium bicarbonate does in the context of TCA toxicity. While they may be used for fluid resuscitation or maintenance, they do not address the metabolic acidosis or the sodium channel blockade that are critical aspects of TCA poisoning treatment.