Home › Guides › ACLS & rhythms
NREMT — Paramedic
Paramedic ACLS & Rhythm Interpretation Review
The paramedic exam tests ACLS as decision architecture, not flashcard rhythms: given a patient and a strip, do you know which branch you're on (arrest vs pulse; shockable vs not; stable vs unstable) and what that branch's signature action is? Most missed questions are branch errors — cardioverting a pulseless patient, pacing a stable bradycardia — rather than strip-reading errors.
This review drills the branch points and the reversible-cause hunt (Hs and Ts) that the exam embeds inside arrest scenarios. Energy settings and drug doses follow your current guidelines and local protocols; the test cares that you choose defibrillation versus synchronized cardioversion versus pacing correctly, and that CPR quality never degrades while you think.
The four branch points
Branch 1 — pulse or no pulse: everything downstream changes. No pulse → CPR now, rhythm analysis, and the shockable/non-shockable split: VF and pulseless VT get defibrillation (unsynchronized) with immediate resumption of compressions; asystole and PEA get high-quality CPR, vasopressor per guidelines, and an aggressive search for reversible causes. Branch 2 — the Hs and Ts: hypovolemia, hypoxia, hydrogen ion (acidosis), hypo-/hyperkalemia, hypothermia; tension pneumothorax, tamponade, toxins, thrombosis (pulmonary and coronary). PEA especially is a 'find the cause' rhythm — narrow-complex/fast suggests mechanical problems (tamponade, tension, hypovolemia); wide/slow suggests metabolic poisoning (hyperkalemia, sodium-channel toxins).
Branch 3 — tachycardia with a pulse: unstable (hypotension, altered mentation, ischemic chest pain, acute heart failure — caused by the rhythm) → synchronized cardioversion; stable → vagal maneuvers/medications per guidelines based on QRS width and regularity. Branch 4 — bradycardia: symptomatic/unstable → atropine first-line per guidelines, then pacing or chronotropic infusion; the tested nuance: high-degree blocks (second-degree type II, third-degree) often respond poorly to atropine — move toward pacing early. Throughout: treat the patient, not the monitor — a 'scary' strip on an asymptomatic patient is a monitor-and-transport answer.
CPR quality and post-ROSC: where exams hide points
Inside every arrest scenario the exam audits the basics: compression rate 100–120, depth, full recoil, interruptions under 10 seconds, compressor rotation every 2 minutes, no hyperventilation (with an advanced airway: continuous compressions and roughly one breath every 6 seconds), waveform capnography to confirm/monitor the airway and CPR quality (persistently very low EtCO2 → improve compressions; sudden sustained rise → suspect ROSC).
Post-ROSC bundle — the most under-studied tested block: support oxygenation to a normal saturation target (avoiding both hypoxia and prolonged hyperoxia), ventilate to normocapnia (do not hyperventilate), treat hypotension per protocol (fluids/vasopressors toward the guideline MAP/SBP floor), obtain a 12-lead (STEMI → PCI destination), check glucose, and keep the patient flat-to-comfortable with temperature management per local protocol. The recurring theme: the post-arrest brain and heart are injured — protect them from the secondary insults (hypoxia, hypotension, hyperventilation) that providers themselves can cause.
Practice questions with answers & rationales
Q1. Your monitor shows a wide-complex tachycardia at 190. The patient is gray, confused, with a barely palpable radial pulse. Drug or electricity?
Answer: Electricity — synchronized cardioversion now (with procedural sedation per protocol if it doesn't delay therapy). Hypotension and altered mentation caused by the rhythm define instability, and unstable tachycardia gets cardioverted rather than medicated. The double-check the exam expects: he has a pulse, so it's synchronized cardioversion; if that pulse vanishes, it becomes defibrillation and CPR.
Q2. Why must the cardioverter be synchronized for unstable tachycardia with a pulse, and what happens if you shock unsynchronized?
Answer: Synchronization times the shock onto the R wave, avoiding the relative refractory period (the T wave's vulnerable phase). An unsynchronized shock landing on the T wave can induce ventricular fibrillation — converting a bad-but-perfusing rhythm into arrest (the R-on-T phenomenon). That's also why VF gets unsynchronized shocks: there's no organized R wave to sync against, and the machine would wait forever.
Q3. Mid-arrest, the rhythm is organized on the monitor but there's no pulse. Your partner suggests pausing for a long pulse check. Better plan?
Answer: That's PEA — continue CPR with minimal interruption and hunt causes: the Hs and Ts. Narrow and fast PEA pushes toward mechanical causes (hypovolemia → fluids; tension pneumothorax → decompress; tamponade → recognize and transport toward definitive care); wide and slow suggests metabolic/toxic (hyperkalemia — dialysis patient? — or sodium-channel blocker overdose) treated per protocol. The exam rewards cause-hunting language over rhythm-watching, and pulse checks stay under 10 seconds at scheduled rhythm checks.
Q4. A dialysis patient arrests; pre-arrest ECG showed flattened P waves and huge peaked T waves with a widening QRS. Which H/T leads, and why does it matter?
Answer: Hyperkalemia — the missed-dialysis history plus peaked T waves and progressive QRS widening is the classic signature. It matters because this arrest has specific protocol-driven antidotal therapy (calcium for membrane stabilization, plus shifting agents per local protocol) without which standard ACLS will likely fail. The exam pattern: histories that point at a reversible cause expect you to name the cause-specific treatment, not just sequence shocks and compressions.
Q5. Symptomatic bradycardia at 32 with hypotension fails to respond to atropine. The strip shows third-degree block. Next move and rationale?
Answer: Transcutaneous pacing (with sedation/analgesia per protocol), or a chronotropic infusion per guidelines where pacing isn't available/effective. Rationale: atropine works on the AV node via vagal withdrawal — in third-degree and type II blocks the disease is below the node, so atropine often does nothing, and guidelines say move to pacing without delay. Verify both electrical and mechanical capture (a pulse matching the paced rate) — pacing without mechanical capture is a tested trap.
Q6. Ten minutes into a resuscitation, EtCO2 jumps from 14 to 42 mmHg. What just happened and what should you not do?
Answer: Suspect ROSC — returning circulation suddenly delivers CO2 to the lungs. Check for a pulse at the next appropriate moment, then pivot to the post-ROSC bundle. What not to do: celebrate by hyperventilating (drops cerebral perfusion), yank the resuscitation apart, or skip the 12-lead and pressure support. The capnography-as-circulation-monitor concept is among the highest-yield ideas on the modern exam.
Q7. Post-ROSC, your patient's BP is 78/40 with SpO2 99% on high-flow oxygen. Name the two corrections the guidelines want.
Answer: Treat the hypotension — fluid bolus and/or vasopressor per protocol toward the guideline floor (commonly cited as SBP ≥ 90 or MAP ≥ 65) — because post-arrest hypotension multiplies brain injury and re-arrest risk; and titrate the oxygen down toward a normal saturation target rather than leaving maximal O2 flowing, since sustained hyperoxia is associated with worse outcomes. Add normocapnic ventilation and a 12-lead, and you've named the bundle the exam is fishing for.
Common mistakes to avoid
- Branch errors: cardioverting pulseless rhythms, defibrillating stable patients, pacing numbers instead of symptoms.
- Letting CPR quality decay while running the algorithm — interruptions, slow rates, leaning on the chest.
- Treating PEA as 'shock-proof asystole' instead of a reversible-cause scavenger hunt.
- Forgetting atropine's poor performance in infranodal blocks — and skipping mechanical-capture verification when pacing.
- Hyperventilating during and after arrest. One breath every 6 seconds with an advanced airway; normocapnia after ROSC.
- Ignoring the post-ROSC bundle (pressure floor, oxygen titration, 12-lead, glucose, temperature) — it's heavily tested and rarely studied.