There is no CPR action in the single-player game of Casualties: Unknown: you play alone, so nobody can do chest compressions on you. When the experiment’s heart stops, you restart it with a defibrillator (an AED or a manual one) used on the upper torso, or with epinephrine, while a worn auto-pump keeps your blood pressure up long enough to try. CPR only appears in a fan-made multiplayer mod, covered at the end.
Casualties: Unknown runs a full cardiovascular simulation, and the heart rarely stops without warning. This guide covers the warning signs, what to do at each stage, every tool that restarts or supports the heart, and how to avoid getting there.
How Cardiac Arrest Happens
The heart usually goes through fibrillation first, an irregular rhythm that worsens in stages. The moodles tell you where you are, and the in-game text is blunt about each one:
| Moodle | What the game says |
|---|---|
| Arrhythmia | “Abnormal heart rhythm… May progress further if the cause isn’t addressed. Can be defibrillated.” |
| Ventricular tachycardia | “Will progress into lethal V-fib if not treated. Can be defibrillated.” |
| Ventricular fibrillation | “Life threatening, chaotic heart rhythm. Asystole is soon to follow.” |
| Cardiac arrest | “Asystole. If you’re somehow conscious, this has a low chance of being treated via defibrillation.” |
The ECG at the bottom of the health panel shows the rhythm, and it flatlines in cardiac arrest. The lesson from that table: shock the heart while it is still fibrillating. A defibrillator fixes fibrillation reliably; once the heart has stopped, each shock only has a small chance of working.
Step-by-Step: What to Do When Your Heart Stops
- Put on an auto-pump if you have one. Its description says it “pumps blood in place of your heart using a simple mechanism and an internal battery, keeping your blood pressure at livable levels. Might buy you more time.” Wear it on your chest; it needs a charged battery.
- Open the health panel with the heart button in the bottom-left corner, and act fast: without blood flow you lose consciousness quickly, and an unconscious experiment cannot use items.
- Drag a defibrillator onto the upper torso. Shock, check the ECG and shock again if it is still flat. The 6.1 patch notes confirm that defibrillators no longer always fix asystole, so expect to need more than one try.
- Use epinephrine if you have no defibrillator, or alongside one. Its description says it “has a low chance to restart the heart if it stops,” and warns that “going over 40ml will cause fibrillation.” Do not empty a whole syringe into yourself.
- Once the heart restarts, fix the cause (blood loss, low oxygen, cold, an overdose) or it will stop again.
AED vs Manual Defibrillator
Both are used on the upper torso and both run on batteries.
- AED (automated external defibrillator). It analyzes your rhythm for you. Its description says it “does not require training, but takes longer to work and uses more power.” It is the easier choice for most runs.
- Manual defibrillator. You set the power yourself. It is “faster and uses less power, but isn’t guaranteed to work,” and “higher INT makes operation easier,” because your Intelligence decides how good the estimate of the right power level is. The manual one also shows your heart rate, blood pressure and oxygen, which is handy when you play without the health chip.
Keep spare batteries charged: a flat defibrillator is dead weight at the worst moment.
Other Items That Help the Heart
- Combat pen. A 100 mL injector that “instantly injects its contents into the body.” The one in the official screenshots holds medical-grade stimulant, epinephrine and oxyline in one shot.
- Oxyline. It “quickly reoxygenates the bloodstream when injected, also stabilizing fibrillation.” Its description also warns of “explosive tendencies when mixed with stomach acid,” so inject it, never drink it.
- Amiodarone. A heart rhythm drug that brings fibrillation down; the 6.1 patch made it work faster.
How to Avoid Cardiac Arrest
Fibrillation starts when your body is under extreme strain. The usual triggers are blood loss that crashes your blood pressure, a racing heart, too much epinephrine, low oxygen and severe cold. That makes bleeding control the best heart medicine in the game. Stop external bleeding with dressings, and treat a hidden bleed with the items in our guide on how to treat internal bleeding. A blast that stops your heart often leaves fragments too, so see how to remove shrapnel once you are stable.
Where CPR Actually Appears
Casualties: Unknown is sold on Steam as a single-player game, and Orsoniks’ 1.0 release does not include co-op. CPR shows up in Casualties: Together (also called KrokMP), a fan-made multiplayer mod on Nexus Mods, where a CPR button sits in the wound view so another player can work on a downed experiment. It is not made or supported by Orsoniks, it needs every player on the same mod version, and how its CPR works can change with any mod update, so its own Nexus page is the place to check before relying on it.
Frequently Asked Questions
Can you do CPR on yourself in Casualties: Unknown? No. There is no self-CPR. Use a defibrillator on the upper torso or epinephrine, and wear an auto-pump to keep blood moving while you try.
Is there CPR in Casualties: Unknown at all? Not in the base game. It appears in the fan-made multiplayer mod Casualties: Together (KrokMP), which is a separate download.
Why does the defibrillator not restart my heart? Shocks fix fibrillation reliably but only have a low chance of fixing a fully stopped heart. Keep trying while you are conscious, and shock earlier next time, while the moodle still says the rhythm “can be defibrillated.”
Does the auto-pump restart the heart? No. It pumps blood in place of your heart to keep your blood pressure livable, which buys time for a defibrillator or epinephrine to restart it.
How much epinephrine is safe? The in-game description warns that going over 40 mL causes fibrillation, so use small amounts rather than a whole syringe.
Which defibrillator should I use? The AED is easier and needs no skill, but uses more battery. The manual defibrillator is faster and cheaper on power, and gets more reliable as your Intelligence rises.