The Chief Complaint
A nurse says:
“Doctor, you need to come to Bed 3. She was just talking to me and now she's not talking at all. I don't think I can feel a pulse.”
You enter the room. The patient is unresponsive.
What is the chief complaint?
Chief complaint: Undifferentiated cardiac arrest.
- No pulse is suspected, but the rhythm and cause are still unknown.
- Go directly to the cardiac arrest/resuscitation algorithm.
Initial Assessment
From the doorway, what do you do immediately? What should the rest of the team be doing at the same time?
ABCs
- Airway: Open? Protected?
- Breathing: Not breathing normally → oxygenate/ventilate.
- Circulation: Check a carotid or femoral pulse for no more than 10 seconds. If there is no definite pulse, start CPR immediately.
At the same time
- Call the code.
- Pads/monitor on.
- IV access → IO if delayed.
- Oxygen/BVM.
- Crash cart to bedside.
No Pulse
You turn on the monitor: regular sinus tachycardia at 120/min. You check a central pulse for no more than 10 seconds: no pulse.
There is no pulse. What happens immediately? What medication do you give, and when?
No pulse
- Start CPR immediately.
- Epinephrine 1 mg IV/IO ASAP.
- Repeat every 3–5 min.
While CPR continues
- Oxygenate/ventilate.
- IV/IO access.
- Rhythm check q2 min.
- Minimize pauses.
- Advanced airway → waveform ETCO₂.
Source
Name the Rhythm
The monitor shows organized electrical activity at 120/min. Repeat pulse check: no pulse.
What rhythm is this? Is it shockable? How is it different from tachycardia with a pulse?
PEA
- Organized electrical activity + no pulse = pulseless electrical activity.
- Not shockable.
Shockable rhythms
- VF.
- Pulseless VT.
Why not shock PEA?
- PEA has organized electrical activity but no effective mechanical circulation.
- Defibrillation treats shockable ventricular tachyarrhythmias—VF and pulseless VT. It does not correct the mechanical/circulatory failure causing PEA.
Source
PEA Physiology
CPR continues.
How can the monitor show organized electrical activity while the patient has no pulse? What is the difference between true PEA and pseudo-PEA?
PEA physiology
- The electrical system can continue to depolarize the myocardium even when the heart cannot generate an effective stroke volume.
- Causes include inadequate preload, mechanical obstruction, severe hypoxia, metabolic derangement, or toxicity. PEA is therefore a clinical state, not one specific arrhythmia.
True PEA
- Organized electrical activity with no meaningful cardiac motion.
Pseudo-PEA
- Cardiac motion is present, but output is too low to generate a palpable pulse.
Action
- Treat both initially as cardiac arrest.
- POCUS can distinguish motion from standstill and help identify the cause → do not delay CPR.
Source
Ongoing Resuscitation
CPR is ongoing and epinephrine has been given.
While you search for the cause, what keeps happening continuously? What findings make you leave the PEA pathway?
Ongoing Resuscitation
- High-quality CPR.
- Oxygenation/ventilation.
- Epinephrine 1 mg IV/IO q3–5 min.
- Rhythm check q2 min.
- Brief pulse check only if organized rhythm.
ETCO₂
- Use with advanced airway.
- Low ETCO₂ → reassess CPR quality/perfusion.
- Sudden rise → think ROSC.
- Goal in this algorithm: >10 mmHg; ideally ≥20 mmHg with effective CPR.
Exit PEA pathway
- VF/pulseless VT → defibrillation pathway.
- Pulse returns → post-arrest care.
Source
Interpreting ETCO₂
- Interpret the value with CPR quality, ventilation, and the cause of arrest; do not use ETCO₂ alone to stop resuscitation.
The Reversible-Cause Differential
During CPR, your attending asks:
“What reversible cause are we looking for?”
What are the six Hs and five Ts in this algorithm? Why is reciting the list not enough?
6 Hs
- H1 — Hypoxia
- H2 — Hypovolemia
- H3 — Hypothermia
- H4 — Hydrogen ion / acidosis
- H5 — Hypo-/hyperkalemia
- H6 — Hypoglycemia
5 Ts
- T1 — Toxins
- T2 — Tension pneumothorax
- T3 — Cardiac tamponade
- T4 — Thrombosis: PE / MI
- T5 — Trauma
Use the Differential
- The Hs and Ts are useful only if they change what you do. Ask: Which cause can I identify and reverse right now?
Algorithm order
- Rapidly reversible causes.
- Chemical resuscitation.
- Procedures / ultrasound.
- Thrombotic causes.
Which mnemonic?
- This is the expanded six-H/five-T framework used in The Chief Complaint PEA algorithm.
- The AHA adult arrest algorithm uses five Hs and five Ts, with pulmonary and coronary thrombosis listed separately.
Source
Box 1 — Rapidly Reversible Causes
Which three Hs does the algorithm put first? How do you recognize and treat each while CPR continues?
H1 — Hypoxia
- Airway/ventilation problem? → oxygen + BVM/advanced airway.
- Intubated? → confirm tube position.
H2 — Hypovolemia
- Hemorrhage/fluid loss? → volume resuscitation.
- Hemorrhage → blood + hemorrhage control.
H3 — Hypothermia
- Low core temperature? → active rewarming / hypothermic arrest pathway.
Why first?
- Hypoxia, hypovolemia, and hypothermia can often be recognized quickly, and treatment can start immediately while CPR continues.
Box 2 — Chemical Resuscitation
A chemistry panel from shortly before the arrest is available.
Which metabolic or toxic causes in the algorithm have specific bedside chemical treatments? When do bicarbonate, calcium, and dextrose belong here?
H4/H5/T1 — Sodium bicarbonate
- Severe hyperkalemia → consider HCO₃.
- Sodium-channel blocker toxicity/TCA → HCO₃.
H5/T1 — Calcium
- Suspected hyperkalemic arrest → consider IV calcium and potassium-shifting treatment while CPR continues.
- Selected calcium-channel blocker toxicity → IV calcium.
H6 — Hypoglycemia
- Check glucose.
- Low → dextrose.
Evidence During Cardiac Arrest
- The 2025 AHA guidelines state that the effectiveness of calcium, bicarbonate, and insulin/glucose in hyperkalemic cardiac arrest is not well established. Use cause-directed treatment without interrupting standard resuscitation.
Source
Box 3 — Procedures + Ultrasound
CPR continues while the team evaluates reversible causes.
Which reversible causes require an immediate procedure? How does POCUS help?
T2 — Tension pneumothorax
- Suspect tension PTX → immediate chest decompression.
- Do not wait for CXR.
- Lung US if immediately available and does not delay treatment.
- See Trauma: Cardiac Arrest Algorithm
T3 — Cardiac tamponade
- Cardiac US → look for pericardial effusion/tamponade.
- Medical arrest → pericardiocentesis.
- Traumatic arrest / penetrating chest trauma → consider resuscitative thoracotomy.
- See Trauma: Cardiac Arrest Algorithm
POCUS
- Look for tamponade, RV dilation/PE, severe hypovolemia, cardiac motion vs standstill.
- Have the probe ready before the pulse check.
- Image during the planned pause → resume CPR immediately.
Rule
- POCUS should answer a focused question without extending the CPR pause.
Source
Box 4 — Thrombotic Cause
During the next pulse check, cardiac ultrasound shows a markedly dilated RV, no pericardial effusion, and bilateral lung sliding.
The nurse says:
“She came in because she suddenly couldn't breathe. Her husband says they got back yesterday from a 12-hour flight. Her left calf looked swollen.”
What cause of PEA just moved way up the list? Which thrombotic diagnoses belong in this box? What treatment should you consider?
Massive PE
- Sudden dyspnea + DVT risk + dilated RV → massive PE high on the list.
- A large PE abruptly raises RV afterload. The RV dilates and fails, less blood reaches the LV, and cardiac output collapses → PEA.
- Strong suspicion during arrest → consider systemic thrombolysis.
- LE US: proximal DVT supports diagnosis if it does not interrupt CPR.
MI
- Coronary thrombosis → coronary reperfusion pathway when clinically appropriate.
Source
ROSC
After treatment for suspected massive PE, the next rhythm check shows an organized rhythm. You feel a carotid pulse. BP 82/48.
What just happened? What changes immediately after the pulse returns?
ROSC
- Return of spontaneous circulation.
After ROSC
- Oxygenate/ventilate.
- Support BP/perfusion.
- 12-lead ECG.
- Treat the arrest cause.
- ICU care.
- Continue definitive PE management.
Teaching
- ROSC is not the end of the resuscitation. The priorities now shift from CPR to supporting perfusion, preventing re-arrest, and treating the cause of the arrest.
Source
Disposition — The ICU Fellow Picks Up
Present the patient in 20 seconds.
“Fifty-eight-year-old woman with sudden dyspnea after recent long-haul travel who had a witnessed PEA arrest in the ED. She received immediate CPR and epinephrine. POCUS showed marked RV dilation without tamponade, and she has unilateral calf swelling, so massive PE is the leading cause. She has ROSC but remains hypotensive and needs ICU-level post-arrest care and definitive PE management.”
Thirty Minutes Later
Thirty minutes later, no ICU bed is available. She remains in the ED. The monitor shows an organized rhythm at 118/min, but you cannot feel a carotid pulse.
What do you do now? Does the fact that she already had ROSC change the immediate arrest treatment? What should you reassess?
Recurrent PEA
- No pulse → restart CPR immediately.
- Epinephrine → nonshockable pathway.
- Re-enter the PEA algorithm.
Reassess
- CPR quality.
- Oxygenation/ventilation.
- Rhythm.
- Hs and Ts.
- Persistent PE vs new reversible cause.
Rapid Fire
Organized electrical rhythm + no pulse?
PEA — pulseless electrical activity.
Shock PEA?
No. PEA is not a shockable rhythm.
Immediate treatment for PEA?
CPR + epinephrine + find the reversible cause.
Epinephrine dose?
Epinephrine 1 mg IV/IO.
Repeat epinephrine?
Repeat epinephrine every 3–5 minutes.
Rhythm checks?
Check the rhythm every 2 minutes. Keep interruptions in compressions brief.
Electrical activity = circulation?
No. Electrical activity does not guarantee effective mechanical circulation or a palpable pulse.
Six Hs in The Chief Complaint algorithm?
- Hypoxia
- Hypovolemia
- Hypothermia
- Hydrogen ion/acidosis
- Hypo-/hyperkalemia
- Hypoglycemia
Five Ts in The Chief Complaint algorithm?
- Toxins
- Tension pneumothorax
- Cardiac tamponade
- Thrombosis: pulmonary embolism or myocardial infarction
- Trauma
Tension PTX?
Immediate chest decompression. Treat suspected tension pneumothorax without waiting for a chest X-ray.
Tamponade?
Cardiac ultrasound and urgent treatment of tamponade. In medical arrest, perform pericardiocentesis; in appropriate traumatic arrest, consider resuscitative thoracotomy.
Hyperkalemia?
Consider IV calcium and potassium-shifting therapy, with bicarbonate when indicated, while CPR continues. Evidence for these treatments during hyperkalemic arrest is limited.
Hypoglycemia?
Give dextrose to correct hypoglycemia.
POCUS during arrest?
Yes, without delaying CPR. Assess cardiac motion, pericardial effusion, and lung sliding during the planned pulse check; do not prolong the pause in compressions.
Massive PE arrest rhythm?
Often PEA. A large pulmonary embolism can obstruct circulation even while electrical activity continues.
Why PEA in massive PE?
A massive pulmonary embolism sharply increases right ventricular afterload. The right ventricle dilates and fails, less blood reaches the left ventricle, and cardiac output collapses.
VF/pulseless VT appears?
Switch to the shockable-rhythm pathway and defibrillate. Continue CPR between rhythm checks and shocks.
Pulse returns?
Begin post–cardiac arrest care. Support oxygenation, ventilation, and blood pressure while treating the cause of the arrest.