# Cardiac Emergency Response

> Cardiac emergency response for Cardiac Technology: CPR parameters, defibrillation energies, shockable versus non-shockable algorithms and peri-arrest drugs.

- Canonical URL: https://prepelephant.com/topics/allied/cardiac-technology/cardiac-emergency-response-ct
- Exam / course: Allied Health · Subject: Cardiac Technology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Cardiac Emergency Response", PrepElephant, https://prepelephant.com/topics/allied/cardiac-technology/cardiac-emergency-response-ct

## Direct answer

When a monitor alarms in the cath lab, the technologist becomes the first responder, and the response runs on a memorised algorithm: compressions at 100-120 per minute, 5-6 centimetres deep, 30:2 with ventilations, interruptions under ten seconds, while the defibrillator charges and the rhythm sorts into shockable (VF and pulseless VT — biphasic 120-200 joules, then CPR, adrenaline 1 mg every 3-5 minutes, amiodarone 300 mg if refractory) or non-shockable (asystole and PEA — adrenaline immediately and every 3-5 minutes, atropine no longer recommended, the 4 Hs and 4 Ts hunted). Peri-arrest care completes the skill set: atropine 0.5-1 mg for unstable bradycardia escalating to transcutaneous pacing, and synchronised cardioversion at graded energies for unstable tachycardias — never unsynchronised on an organised rhythm.

## What you must remember

- **Compression grammar:** 100-120 per minute, depth 5-6 cm, full recoil, 30:2 ratio, compressor switch every two minutes with rhythm checks, interruptions always under 10 seconds — compressions continue while the defibrillator charges.
- **Defibrillation numbers:** biphasic 120-200 J (follow manufacturer default; monophasic 360 J), pads anterolateral (or anteroposterior), chest dry and shaved where needed, oxygen sources detached, and compressions resumed the instant the shock is delivered.
- **Shockable pathway:** VF/pulseless VT — shock, two minutes CPR, adrenaline 1 mg IV/IO every 3-5 minutes from around the second cycle, amiodarone 300 mg bolus for refractory VF (a further 150 mg may follow), lidocaine 1-1.5 mg/kg the alternative.
- **Non-shockable pathway:** asystole/PEA — CPR and adrenaline 1 mg every 3-5 minutes immediately; atropine is no longer recommended; the rescuers run the reversible causes — hypoxia, hypovolaemia, hyper/hypokalaemia and other metabolic, hypothermia, thrombosis coronary, thrombosis pulmonary, tamponade, tension pneumothorax, toxins.
- **Unstable bradycardia ladder:** atropine 0.5-1 mg IV repeated to a maximum of 3 mg; if ineffective, transcutaneous pacing (rate 70-80, output raised until capture, analgesia and sedation) or infusion (dopamine, adrenaline) as a bridge.
- **Synchronised cardioversion energies (biphasic):** narrow regular (SVT, flutter) start 50-100 J; irregular narrow (AF) 120-200 J (defibrillator-level, unsync-capable dose); regular wide 100 J — always with sync confirmed on the R wave.
- **Post-ROSC checklist:** 12-lead ECG, oxygen titrated to 92-98 per cent saturations, mean arterial pressure at 65 mmHg or more, targeted temperature management — the technologist's data drive the first hour.

## A code blue, narrated for the technologist

A post-angiography patient in the recovery bay slumps; the monitor shows coarse ventricular fibrillation. The technologist calls the code and starts compressions at a metronome of 110 while a colleague applies pads anterolateral. The defibrillator is charged during compressions, the safety call made, the shock delivered, and compressions resumed within seconds. Two minutes later the rhythm check shows an organised rhythm — a pulse is found; post-ROSC care begins with a 12-lead ECG and blood-pressure support. Rewind with asystole: no shock — immediate CPR and adrenaline 1 mg while one member recites the 4 Hs and 4 Ts; that branch difference is the algorithm's entire intellectual content. The technologist also owns the environment: oxygen off before the shock, suction and intubation kit in reach, and the event timeline recorded for the audit that follows every code.

## Where students slip

The high-yield errors are procedural. Compressions stopping while the defibrillator charges is the classic error — charge during CPR and shock within seconds of the pause. Synchronised mode is left on for VF and the defibrillator refuses to fire (no R wave exists) — the inverse error, shocking unsynchronised through an organised tachycardia, risks current on the T wave inducing VF. The atropine question betrays outdated knowledge: it was removed from the cardiac arrest algorithm for asystole and PEA, though it remains first-line for symptomatic bradycardia — two facts candidates conflate. Amiodarone's place is misquoted as first-cycle; per classic teaching it enters after the third shock in refractory VF. The pulse is palpated only when an organised rhythm appears; otherwise compressions resume within ten seconds. Finally, pads over an implanted device are avoided by a hand's breadth, and documentation — times, interventions, rhythm strips — belongs to whoever watched the monitor: usually the technologist.

## Frequently asked questions

### What are the parameters of high-quality chest compressions?

Rate 100-120 per minute, depth 5-6 centimetres with full recoil, 30:2 with ventilations, compressor rotation every two minutes, and interruptions kept under ten seconds. Compressions continue while the defibrillator charges.

### What energy is used for defibrillation of ventricular fibrillation?

A biphasic shock of 120-200 joules (following the device's default; 360 J if monophasic), followed immediately by resumed compressions. Subsequent shocks may be equal or higher per protocol.

### Why is atropine no longer used in cardiac arrest?

Atropine showed no benefit in asystole or pulseless electrical activity and was removed from the arrest algorithm. It remains first-line for symptomatic bradycardia, up to 3 mg total, before pacing.

### Which reversible causes must be hunted during a non-shockable arrest?

The 4 Hs — hypoxia, hypovolaemia, hypo/hyperkalaemia and metabolic derangement, hypothermia — and the 4 Ts: thrombosis (coronary), thrombosis (pulmonary), tension pneumothorax and tamponade, plus toxins. PEA survives only when its cause is found.

### How does synchronised cardioversion differ from defibrillation?

Synchronisation times the shock to the R wave, avoiding delivery on the T wave, and is mandatory for organised tachycardias with a pulse; defibrillation is unsynchronised and reserved for VF or pulseless VT. Energies for sync cardioversion start lower and are graded by rhythm.