Cardiology

TCA Toxicity and Bicarbonate: Mechanism

Sodium bicarbonate has become the mainstay treatment for arrhythmias caused by TCA toxicity.

The cardiotoxic effects of TCA work via blockade of the rapid sodium channels (see below- stage 0).

There will be a characteristic prolongation of the QRS. Potentiating hemodynamic instability.

HOW DOES BICARBONATE HELP?

The benefit of sodium bicarbonate (NaHCO3) is primarily related the sodium component. Increasing the extracellular sodium concentration results in an increase of the electrochemical gradient across cardiac cell membranes. This in effect works to attenuate the TCA-induced blockade of rapid sodium channels.

Also the alkalization of the blood from bicarbonate shifts TCA towards its non-ionized form, reducing its ability to bind sodium channels.

REFERENCES

  1. Sasyniuk BI, Jhamandas V. Mechanism of reversal of toxic effects of amitriptyline on cardiac Purkinje fibers by sodium bicarbonate. J Pharmacol Exp Ther. 1984;231(2):387.
  2. Bruccoleri RE, Burns MM. A Literature Review of the Use of Sodium Bicarbonate for the Treatment of QRS Widening. J Med Toxicol. 2016 Mar;12(1):121-9.
Get Medical Pearls directly to your inbox every week!
Weekly posts with high yield medical knowledge, directly to your mailbox!
Dr. C Humphreys

Internal Medicine

Recent Posts

Older Age and Obstructive Sleep Apnea (OSA): Mechanism

Older age is recognized as a risk factor for obstructive sleep apnea.[1] But why? Suspected…

2 months ago

How does Weight Affect Obstructive Sleep Apnea (OSA): Mechanism

Being overweight (BMI ≥ 25 kg/m2)/Obese (BMI ≥ 30 kg/m2) is one of the most…

2 months ago

Nocturia and OSA: Mechanism

Nocturia is a common symptom associated with obstructive sleep apnea. [1] Img Cred: Am J…

1 year ago

ASD vs. VSD Murmur Difference

ASD (Atrial Septal Defect) Wide, Fixed split S2 (in contrast to the normal variation in…

1 year ago

Mechanism of a Mixed Apnea

Mixed apneas are characterized by absent respiratory effort and airflow in the first section of…

2 years ago

How Does Hypothyroidism Cause Hypoventilation?

Although rare, the differential diagnosis of hypoventilation and hypercapnia respiratory failure includes hypothyroidism. It is…

2 years ago

This website uses cookies.