3.2 Core Workflows and Decision Points

The Adult Cardiac Arrest Algorithm

The adult cardiac arrest algorithm is the single most tested workflow in this domain. Everything is built on a foundation of high-quality CPR: a rate of 100-120 compressions per minute, a depth of 2-2.4 inches (5-6 cm), full chest recoil between compressions, and minimizing interruptions so the chest-compression fraction stays above 60%. Without an advanced airway use a 30:2 compression-to-ventilation ratio; once a supraglottic airway or endotracheal tube is in place, deliver continuous compressions with one breath every 6 seconds (10/min) asynchronously.

The first branch point is rhythm. Attach the monitor/defibrillator and decide: shockable (VF/pVT) or non-shockable (asystole/PEA).

Shockable branch (VF / pVT)

1. Defibrillate with a single biphasic shock at the manufacturer-recommended energy (commonly 120-200 J; use 360 J if monophasic), then immediately resume compressions for a 2-minute cycle.
2. Establish IV/IO access. Give epinephrine 1 mg IV/IO after the first shock fails, then every 3-5 minutes.
3. For VF/pVT that persists after shocks, give an antiarrhythmic: amiodarone 300 mg IV/IO, with a repeat dose of 150 mg if needed (cumulative ceiling 2.2 g/24 h), or lidocaine 1-1.5 mg/kg then 0.5-0.75 mg/kg.
4. Reassess rhythm and pulse every 2 minutes, swapping compressors to limit fatigue.

Non-shockable branch (asystole / PEA)

Do not shock. Give epinephrine 1 mg as soon as feasible and repeat every 3-5 minutes, continue CPR, and aggressively treat reversible causes. PEA in particular is a cause-driven rhythm - the rhythm on the screen will not improve until the underlying problem is fixed.

ACLS Arrest Drugs and the H's and T's

Note that vasopressin and routine sodium bicarbonate/calcium are not part of the standard algorithm; bicarbonate and calcium are reserved for specific causes such as hyperkalemia or known acidosis/toxicity.

Reversible causes - the H's and T's

Every arrest, especially PEA and asystole, demands a search for treatable causes:

• H's: Hypovolemia, Hypoxia, Hydrogen ion (acidosis), Hypo-/Hyperkalemia, Hypothermia.
• T's: Tension pneumothorax, Tamponade (cardiac), Toxins, Thrombosis (pulmonary embolism), Thrombosis (coronary/MI).

Match the clue to the fix: hypovolemia gets fluids, tension pneumothorax gets needle decompression, hyperkalemia gets calcium plus bicarbonate, and a suspected massive PE may warrant thrombolytics per protocol.

Recognizing ROSC

Watch waveform capnography. A sudden, sustained rise in ETCO2 (often jumping toward or above 35-40 mmHg) during compressions is an early, hands-on-chest sign of return of spontaneous circulation - confirm with a pulse check. Conversely, a persistent ETCO2 under 10 mmHg after 20 minutes of high-quality CPR is a strong predictor of failure to achieve ROSC and informs termination decisions per local protocol.

Running the Code as Team Leader

Paramedic exam items increasingly test resuscitation leadership, not just drug doses. The team leader keeps the metronome of the algorithm: assign a compressor, an airway provider, an IV/IO and medication provider, and a recorder; rotate compressors every 2 minutes at the rhythm check to prevent fatigue-related shallow compressions. Call out the time of each epinephrine dose so the every-3-to-5-minute interval is honored, and announce the rhythm decision aloud at each check so the team shocks or does not shock without hesitation.

The quality of CPR is the intervention that most influences survival, so the leader continuously monitors chest-compression fraction (aim above 60%), depth, rate, and recoil, using the capnography number and any feedback device as objective data. Pre-charge the defibrillator before the rhythm check so that, if VF/pVT is present, the shock is delivered within seconds and compressions resume immediately - the goal is a peri-shock pause under 10 seconds.

Sequencing in the shockable branch

A clean mental sequence prevents missed steps: shock, then 2 minutes of CPR, then rhythm check; if still VF/pVT, shock again, give epinephrine, then 2 minutes of CPR; next cycle, shock, give amiodarone 300 mg, CPR. Interleaving drugs between shocks (rather than stopping CPR to push them) keeps the chest-compression fraction high. Throughout, the H's and T's are revisited every cycle - a code that is not responding usually has an uncorrected reversible cause hiding in that list.

Access, Airway Timing, and Drug Routes

Vascular access in arrest is IV or IO - intraosseous access is fast, reliable, and fully acceptable for every arrest medication when a peripheral IV is not immediately available. All standard arrest drugs (epinephrine, amiodarone, lidocaine) are given by the same dose IV or IO. Endotracheal drug administration is a last resort, uses higher doses, and is not preferred. The exam expects you to know that establishing access never takes priority over compressions and defibrillation; assign it to a team member while CPR continues.

Airway management in arrest has shifted toward not interrupting compressions to intubate. A bag-mask with a good seal or a supraglottic airway placed without pausing compressions is appropriate early; definitive intubation can wait until it does not cost compression time. Once any advanced airway is in place, switch to continuous compressions with asynchronous ventilation at one breath every 6 seconds, and use waveform capnography both to confirm tube placement (a persistent square-wave capnogram) and to monitor CPR quality and detect ROSC.

A sudden loss of the capnography waveform after a confirmed tube means a dislodged or obstructed tube, not necessarily a worsening patient - check the airway first.