The nurse is caring for an adult patient who has gone into ventricular fibrillation.
When assisting with defibrillating the patient, what must the nurse do?

Choice A rationale

Sarin gas is an extremely potent organophosphate nerve agent that inhibits acetylcholinesterase at the neuromuscular junction and within the central nervous system. This inhibition leads to a cholinergic crisis characterized by excessive bronchial secretions, bradycardia, and muscle paralysis. Treatment requires atropine to block muscarinic receptors and pralidoxime to reactivate the enzyme. Ciprofloxacin, being a fluoroquinolone antibiotic targeting bacterial DNA gyrase, has no biochemical mechanism to counteract nerve gas toxicity or its physiological effects.

Choice B rationale

Ebola virus causes a severe hemorrhagic fever by inducing widespread endothelial damage and a massive cytokine storm. As a viral pathogen, it replicates using host cell machinery which is unaffected by the mechanism of ciprofloxacin. Ciprofloxacin specifically targets the A subunit of bacterial DNA gyrase and topoisomerase IV, enzymes absent in viruses. While secondary bacterial infections may occur in Ebola patients, ciprofloxacin is not part of the primary treatment regimen for the viral disaster itself.

Choice C rationale

Anthrax is caused by the Gram-positive, spore-forming bacterium Bacillus anthracis. Ciprofloxacin is the gold standard for post-exposure prophylaxis and treatment because it inhibits the bacterial enzymes necessary for DNA replication and transcription. In a bioterrorism event involving aerosolized spores, rapid administration of fluoroquinolones prevents the bacteria from multiplying and releasing lethal toxins. It is highly effective against most strains, making it a critical component of the Strategic National Stockpile for such specific bacterial threats.

Choice D rationale

Smallpox is caused by the variola virus, a large DNA orthopoxvirus. Historically, it was eradicated through vaccination, but it remains a bioterrorism concern. Being a viral entity, variola does not possess the DNA gyrase targets that ciprofloxacin acts upon. Treatment for smallpox focuses on antiviral medications like tecovirimat, which interferes with the viral envelope protein. Ciprofloxacin provides no clinical benefit against the variola virus and is not indicated for smallpox prophylaxis in disaster management protocols.

Choice A rationale

In a third-degree AV block, the atria and ventricles operate independently, but their individual rhythms are typically regular. The SA node continues to fire, leading to a regular PP interval, while a secondary pacemaker in the AV junction or ventricles triggers the QRS complexes, leading to a regular RR interval. The lack of conduction between them does not inherently make the intervals irregular; it simply means there is no physiological relationship or synchrony between the two.

Choice B rationale

Third-degree heart block, or complete heart block, is characterized by a total failure of conduction between the atria and ventricles. The atrial rate, governed by the SA node, is normally 60 to 100 beats per minute. The ventricular escape rhythm is much slower, typically 20 to 40 beats per minute if originating in the ventricles. Because the atrial rate is faster than the independent ventricular rate, the ECG will show more P waves than QRS complexes.

Choice C rationale

The PP interval represents the atrial rate, and the RR interval represents the ventricular rate. In complete heart block, the atria usually beat at a normal physiological rate, whereas the ventricles beat at a much slower escape rate. Therefore, the PP interval will be significantly shorter than the RR interval. If these intervals were equal and a relationship existed, it would suggest a coordinated rhythm rather than the complete dissociation seen in a third-degree atrioventricular block.

Choice D rationale

A constant PR interval requires a consistent relationship where each QRS complex is triggered by a preceding P wave after a specific delay. In third-degree AV block, there is no relationship between P waves and QRS complexes. The P waves appear to march through the QRS complexes and T waves at their own pace. Because the atrial and ventricular activities are dissociated, the distance between any given P wave and the following QRS complex varies randomly.