By Abdolghader Pakniyat (Reviewed by Dr. Sabrina Berdouk )
Educational content for adult resuscitation. Follow your local AHA/ERC guidelines and institutional protocols. POCUS is operator-dependent.
By Part 3, the question is no longer whether ultrasound has a role in cardiac arrest.
The real question is simpler and harder:
What should POCUS actually change?
Not every finding deserves an action.
Not every image deserves a pause.
And not every abnormality deserves treatment.
AHA 2025 states that intra-arrest POCUS diagnosis and prognostication are not well established; selected use by experienced clinicians may be considered if it does not interrupt resuscitation. ERC 2025 likewise restricts scanning to skilled operators without additional/prolonged pauses, warns against diagnosing PE from isolated RV dilation, and rejects myocardial contractility as the sole reason to terminate CPR. AHA; ERC.
This post is the action piece of the series:
what to do next when POCUS shows something meaningful during CPR.
The non-negotiable rules
Before any pathway, keep the same discipline from Parts 1 and 2:
- CPR is the treatment.
- ECG leads shock decisions.
- One pause = one primary question.
- Acquire during the pause. Interpret during compressions.
- If scanning prolongs the pause, stop scanning.
Plan the scan before the pause. Lost compression time reduces coronary perfusion, so a better image can come at a physiological cost. Prepare the probe and question during compressions, record briefly within the existing check, then review after compressions restart. Structured workflows can shorten interruptions, but are not proof of improved survival. AHA BLS; CASA workflow study.
Step 1: Decide whether this should be a scan cycle
Do not scan reflexively.
Scan only if three conditions are true:
- A trained sonographer is available
- A timekeeper is controlling the pause
- The answer could change management now
If not, do not scan. High-quality CPR wins.
Step 2: Use one fixed loop every cycle
During compressions
Choose the one question for the next pause.
Pre-position the probe and identify the window before compressions stop.
Use ongoing compressions for parallel tasks that do not steal pause time, such as DVT scanning, airway confirmation, or abdominal free-fluid assessment when clinically relevant.
During the planned pulse/rhythm check
Record one brief clip within the existing planned check. Keep the total pulse check to no more than 10 seconds; ultrasound gets no extra time. If the image or pulse is unclear, restart compressions immediately. AHA BLS.
Immediately after
Back on the chest.
During compressions again
Interpret the clip.
Announce the decision, not the image.
The decision pathways
1) Obstructive pathway
The obstructive pathway can identify urgently treatable causes when the clinical context and reliable imaging agree.
These are adult decision aids. In traumatic arrest, follow the dedicated pathway: correct hemorrhage, hypoxia, tension pneumothorax and tamponade urgently. Continue compressions unless they delay those interventions. RCUK traumatic-arrest guidance.
Tamponade
When to suspect it: PEA or profound shock in the right trauma or medical context.
What POCUS may show: pericardial fluid with supportive tamponade physiology, such as right-sided chamber collapse. Effusion alone is not tamponade; conversely, absent RV collapse in one example is not a universal exclusion rule. Interpret the findings with hemodynamics and the arrest context. ESC pericardial guidance.
What to do next:
For likely medical tamponade causing arrest, mobilize expert ultrasound-guided drainage immediately while continuing resuscitation. Traumatic or postoperative tamponade requires its dedicated surgical pathway, including resuscitative thoracotomy or emergency resternotomy when indicated. Needle drainage must not delay definitive treatment. POCUS must not delay treatment when the clinical diagnosis is compelling. RCUK traumatic-arrest algorithm; AHA special-circumstances guidance.
What not to do:
Do not spend extra pauses trying to make the picture prettier.
If the physiology and context fit, move to action.
Tension pneumothorax
When to suspect it: obstructive physiology, ventilation difficulty, trauma, severe asthma, or a clinical context that fits.
What POCUS may show: absent sliding with other compatible findings can support pneumothorax, but absent sliding alone is nonspecific. Genuine lung sliding, B-lines or lung pulse exclude pleural air at the examined point, not throughout the entire chest. Do not delay treatment of strongly suspected tension pneumothorax to complete a scan.
What to do next: treat strongly suspected tension pneumothorax immediately with decompression by a trained clinician using the appropriate local medical or trauma pathway. Do not wait for ultrasound confirmation or create a lung-scanning pause. RCUK special circumstances.
What not to do:
Do not turn the pause into a long bilateral lung survey.
Presumed pulmonary embolism
This is where clinicians get into trouble.
When to suspect it: a compatible collapse, thromboembolic risk and supporting findings. PE often presents with PEA; suspicion should not wait for prolonged refractory arrest. AHA.
What POCUS may show: RV enlargement, septal flattening and an underfilled LV can support the clinical suspicion, but RV enlargement may also develop as a consequence of arrest. Proximal DVT supports venous thromboembolism; it does not prove the cause of arrest. No isolated RV:LV ratio establishes PE during CPR. ILCOR; RCUK.
What to do next: continue CPR and activate the local PE-arrest team. For suspected PE, AHA 2025 allows consideration of fibrinolysis; ERC/RCUK recommends it when PE is the suspected cause. Weigh bleeding risk and competing diagnoses. For confirmed PE, AHA lists fibrinolysis, surgical or percutaneous embolectomy as reasonable options, with ECPR for selected patients. Selection needs expertise and resources. The 2026 PE guideline adds a qualification: in category E2 (refractory shock or prolonged arrest) without mechanical circulatory support, surgery is not recommended over other advanced therapies to prevent short-term mortality. This is not a blanket prohibition of surgery. AHA 2025; RCUK; AHA/ACC 2026.
After fibrinolysis, ERC/RCUK advises considering 60–90 minutes of CPR in selected patients; AHA states that the optimal duration is uncertain. Follow the local PE-arrest pathway. RCUK ALS; AHA.
What not to do:
Do not diagnose PE from RV dilation alone.
Do not let isolated RV dilation alone drive thrombolysis.
That is exactly the overcall ERC warns against. (ERC)
2) Hypovolemia / hemorrhage pathway
This is the “empty heart / low volume” branch.
When to suspect it: trauma, ruptured ectopic, GI bleed, massive volume loss, or an “empty” cardiac pattern.
What POCUS may show: small, underfilled chambers and, when organized myocardial contraction is present, a hyperdynamic LV. These findings can suggest low filling but do not prove hemorrhage or fluid responsiveness. IVC appearance during CPR should not be used alone.
What to do next: continue resuscitation and treat the likely cause. If hemorrhage is suspected, mobilize blood and definitive bleeding control through the local pathway; other causes of low filling require cause-specific treatment. FAST or abdominal scanning may provide supporting evidence during compressions without delaying care.
A negative FAST does not exclude major bleeding. Do not let it delay hemorrhage control when the clinical evidence is compelling; further imaging depends on whether the patient can be stabilized. European trauma guidance.
What not to do:
Do not over-trust the IVC during CPR.
The review states that CPR physiology, ventilation, and venous congestion can distort IVC interpretation.
3) Airway / ventilation pathway
Sometimes the fastest life-saving decision is not cardiac—it is airway or lung.
When to suspect it: oxygenation failure, difficult ventilation, uncertain tube position, unilateral lung findings, asthma/COPD physiology, or possible mainstem intubation.
What POCUS may show: transtracheal imaging and lung findings can assist with airway troubleshooting. Use sustained waveform capnography alongside clinical assessment to confirm and continuously monitor tracheal tube placement; ultrasound is an adjunct and must not delay correction of an obvious airway problem. AHA ALS.
What to do next: troubleshoot oxygenation and ventilation while CPR continues. Check the capnography trace, tube position and patency, and breathing circuit. Sustained exhaled CO₂ does not exclude mainstem intubation. An absent trace requires urgent exclusion of esophageal placement; do not explain it away as cardiac arrest or wait for ultrasound. PUMA airway guidance.
What not to do:
Do not let a lung image delay correction of an obvious airway problem.
4) Cardiac activity pathway
This pathway does not tell you whether to shock.
It tells you how to focus the resuscitation when ECG is organized or unclear.
Pseudo-PEA
When to suspect it: organized electrical activity on the monitor, no palpable pulse, but visible cardiac contraction on ultrasound.
Why it matters: visible contraction may coexist with inadequate forward flow. Better outcomes reported in observational studies do not make cardiac activity a reliable individual prognosis; definitions, scan timing and treatment decisions introduce bias. ILCOR evidence review.
What to do next: resume CPR unless spontaneous perfusion is confirmed. Cardiac motion alone is not ROSC. Treat the likely reversible cause and reassess the clinical and physiological response. AHA ALS.
What not to do:
Do not mistake valve flicker, blood swirl, or transmitted motion for meaningful contraction.
Fine VF / occult shockable rhythm
This deserves a separate sentence because it changes treatment immediately.
Unexpected fibrillatory myocardial movement on POCUS should prompt rapid correlation with the ECG and the applicable ALS defibrillation algorithm, without extending the pause. Defibrillate VF/pVT promptly, including fine VF. ERC 2025 also advises a shock when an ALS provider is uncertain whether the monitor displays fine VF or asystole; do not wait for ultrasound certainty or another expert before an indicated shock. Observational occult-VF evidence does not establish a universal ultrasound-only shock rule for every ECG-nonshockable arrest. Prospective multicenter study; ERC 2025, page 18; AHA ALS.
What to do next:
Shock if the rhythm is truly shockable.
Then resume CPR immediately.
What not to do:
Do not turn ultrasound into a long rhythm debate.
Defibrillation should not be delayed to collect a better clip.
Cardiac standstill
What it means: standstill is associated with poor outcomes, but cannot establish futility. Intra-arrest ultrasound prognostication remains unreliable. ILCOR.
Cardiac activity is associated with better resuscitation outcomes in observational studies, but definitions and interpretation vary. One physician-sonographer clip study found only moderate agreement on standstill. These findings do not establish a stand-alone prognostic or termination rule. Interpretation study; AHA guidance.
What to do next: resume CPR and address reversible causes. Any termination decision must follow the appropriate local pathway and full clinical assessment, not an ultrasound-only prediction. ILCOR.
What not to do:
Do not use myocardial contractility on POCUS as the sole reason to terminate CPR. Both AHA and ERC caution against that. (cpr.heart.org)
Optional add-on: Ultrasound-assisted pulse checks
Selected studies suggest ultrasound may improve pulse detection, but results depend on technique and setting. One prospective study of 54 patients with femoral arterial lines found Doppler more accurate than palpation over 213 pulse checks. This does not make every B-mode/color method a validated replacement for multimodal ROSC assessment or justify extra pause time. Primary study.
But the rule from Part 2 still applies:
- Set up during compressions
- Interpret only during the planned pulse check
- Time-box it
- If unclear → hands back on chest
ROSC requires evidence of spontaneous circulation. Integrate rhythm, perfusion signs, ETCO₂ trends and a spontaneous arterial pressure waveform if available. Compression-generated pulsatility, cardiac motion or an ETCO₂ rise alone does not establish ROSC. If uncertain at the planned check, resume CPR. AHA intra-arrest monitoring.
The bedside summary
When POCUS shows a meaningful finding during CPR, the practical response is simple:
- Tamponade pattern + context → urgent cause-appropriate drainage: medical tamponade may need pericardiocentesis; traumatic/postoperative tamponade requires the dedicated surgical pathway
- Tension PTX likely → decompress
- RV dilation alone → not enough for PE
- Hyperdynamic underfilled LV → think hypovolemia / hemorrhage
- Contraction present → pseudo-PEA physiology
- Suspected occult VF on ultrasound → rapidly correlate with the ECG and apply the relevant ALS defibrillation guidance; do not delay an indicated shock to obtain or interpret a scan.
- Standstill → not a validated futility test; never an ultrasound-only stop decision
CPR is still the treatment. POCUS earns its place only when it changes the next step without delaying it.
Sources: 2024 clinical review; 2025 Resuscitative Ultrasound chapter; AHA 2025 adult ALS; ERC 2025 adult ALS. The review and textbook are educational sources; current guideline recommendations and local competence govern bedside use.
Clinical caution: Isolated RV dilation does not establish PE, and ultrasound appearance alone is not a universal shock-decision rule. Use the qualified pathways above.
