DCAS Cardiac Emergencies (ACLS) 3 — Questions and Answers
Question 1: Adenosine is used to treat which arrhythmia?
- Stable narrow-complex supraventricular tachycardia (SVT) with regular rhythm (Correct answer)
- Ventricular tachycardia with pulse
- Atrial fibrillation with rapid ventricular rate
- Ventricular fibrillation
Correct answer: Stable narrow-complex supraventricular tachycardia (SVT) with regular rhythm
Adenosine transiently blocks the AV node, terminating re-entry SVTs; its extremely short half-life (10 seconds) makes it safe even if the diagnosis is uncertain — it will terminate AV-nodal-dependent arrhythmias or cause diagnostic slowing.
Question 2: Cardioversion for unstable tachyarrhythmia is performed 'synchronised' meaning:
- The shock is delivered on the R wave to avoid inducing VF (Correct answer)
- The shock is delivered at random timing
- Energy is matched to the patient's body weight
- Two defibrillators are used simultaneously
Correct answer: The shock is delivered on the R wave to avoid inducing VF
Synchronised cardioversion delivers the shock on the QRS complex (R wave), avoiding delivery during the vulnerable T wave repolarisation period which could induce ventricular fibrillation.
Question 3: A patient presents with SVT at 200 bpm, BP 90/60, diaphoretic, and confused. The ACLS treatment is:
- Immediate synchronised cardioversion (Correct answer)
- Adenosine 6mg IV rapid push
- Diltiazem 20mg IV
- Vagal manoeuvres
Correct answer: Immediate synchronised cardioversion
Haemodynamic instability (hypotension, altered consciousness, diaphoresis) requires immediate synchronised cardioversion rather than pharmacological attempts, which take time and may fail.
Question 4: Which waveform on capnography indicates return of spontaneous circulation (ROSC) during CPR?
- Sudden sustained increase in ETCO2 to >35-40 mmHg (Correct answer)
- A flat waveform
- ETCO2 drops below 10 mmHg
- Waveform becomes irregular and irregular
Correct answer: Sudden sustained increase in ETCO2 to >35-40 mmHg
During CPR, ETCO2 reflects cardiac output; when ROSC occurs, the heart suddenly resumes pumping blood through the lungs, causing a sudden and sustained rise in ETCO2, providing a non-invasive indicator of ROSC.
Question 5: High-quality CPR requires that chest recoil between compressions is:
- Complete (full recoil between each compression) without leaning on the chest (Correct answer)
- Partial recoil to maintain constant pressure
- Irrelevant to outcomes
- Achieved only by changing rescuers frequently
Correct answer: Complete (full recoil between each compression) without leaning on the chest
Complete chest recoil between compressions allows ventricular filling (diastolic filling) during CPR; leaning on the chest prevents recoil, reduces venous return, and significantly reduces coronary and cerebral perfusion.
Question 6: The first medication to administer in the ACLS algorithm for asystole is:
- Epinephrine 1mg IV/IO every 3-5 minutes (Correct answer)
- Atropine 1mg IV
- Sodium bicarbonate
- Calcium chloride
Correct answer: Epinephrine 1mg IV/IO every 3-5 minutes
Asystole and PEA are both treated with CPR and epinephrine every 3-5 minutes; atropine is no longer recommended in ACLS for asystole as it has not been shown to improve outcomes.
DCAS Cardiac Emergencies (ACLS) 3
Adenosine is used to treat which arrhythmia?