(Part 2 of the POCUS in CPR & Critical Care series)

By Abdolghader Pakniyat (Reviewed by Dr. Sabrina Berdouk)

Educational content only. Follow your local AHA/ERC guidelines and institutional protocols. POCUS is operator-dependent.

POCUS can clarify uncertainty during cardiac arrest.
It can also mislead teams into false confidence.

Ultrasound can cause harm through poor acquisition, misinterpretation, over-trust or delayed action.

This post focuses on the common pitfalls of sonography during cardiac arrest and how to avoid turning a decision tool into a distraction.

The Core Problem

Most ultrasound findings during arrest are supportive and must be interpreted in context.

POCUS does not give answers.
It gives clues.

When clues are treated as conclusions, patients are harmed.

Pitfall #1: Treating POCUS as a Diagnosis Instead of Context

Common examples:

• RV dilation → “This must be PE”
• Any Effusion → “This is tamponade”
• Any motion → “There is a pulse”
• No motion → “We should stop”

Reality:

• Most findings during arrest are supportive, not definitive.
• Interpretation must include timing, physiology, and the clinical story.
• POCUS should narrow uncertainty, not replace thinking.

An effusion is fluid; tamponade is impaired cardiac filling from pericardial pressure. Confirm that the collection is pericardial: pleural fluid and epicardial fat can mimic an effusion. Effusion size alone does not establish tamponade: rapid accumulation may cause collapse with relatively little fluid. Integrate the effusion, chamber compression and clinical context. If tamponade is the likely cause of arrest, arrange urgent drainage through the appropriate local pathway without delaying resuscitation. ESC pericardial guidance; ACC imaging guidance.

Pitfall #2: False Cardiac “Activity”

Not all motion is contraction.

Common mimics:

• Valve flutter
• Blood swirl
• Ventilator-transmitted motion
• CPR-transmitted movement

Rule that protects you:

• True contraction requires myocardial thickening and shortening.
• If the image is uncertain, describe it as indeterminate rather than definite standstill; continue CPR unless the clinical assessment establishes ROSC.
• Motion ≠ perfusion.

Pitfall #3: Cardiac Standstill Misused as a Stop Rule

Cardiac standstill is associated with poor outcomes, but the evidence is limited by scan timing, inconsistent definitions and unblinded decisions to stop resuscitation. This can create a self-fulfilling prediction. Intra-arrest ultrasound is not a validated futility test. ILCOR evidence review.

A small number of patients with sonographic standstill still achieve ROSC.

Key rule:

• Do not use standstill to make a stand-alone prognosis.
• Never use “no motion” as the sole reason to terminate resuscitation.
• Follow your local termination-of-resuscitation pathway and the full clinical picture.

Pitfall #4: RV Dilation ≠ Pulmonary Embolism

RV dilation during arrest is common, especially:

• Late in arrest
• With severe hypoxia or acidosis
• After prolonged low-flow states

RV enlargement may develop after arrest as blood redistributes to the right heart. It does not establish what caused the arrest. ERC guidance warns against diagnosing PE from RV dilation alone. ILCOR physiology and evidence review; RCUK 2025.

Build suspicion from concordant findings. The following is a clinical reasoning aid, not a validated PE score:

• Compatible story and risk factors
• Early RV strain, while recognizing that this remains nonspecific
• Supporting evidence obtained without interrupting compressions, such as proximal DVT; this supports venous thromboembolism but does not by itself prove the cause of arrest.

Isolated RV dilation, especially late, should not drive thrombolysis. Treat PE as “presumed” only when the overall scenario supports it.

Pitfall #5: Lung Ultrasound Overconfidence

Absent lung sliding is not specific.
It can be caused by:

• Mainstem intubation
• Atelectasis
• Pleurodesis
• Apnea

High-yield arrest pitfall:

• Absent sliding with lung pulse often suggests airway/atelectasis (including mainstem) rather than pneumothorax.

Safer rule:

• Interpret specific signs at the scanned location: genuine lung sliding, B-lines or lung pulse exclude pneumothorax at that point, whereas absent sliding alone is nonspecific. A negative or limited scan does not exclude pneumothorax elsewhere or justify delaying treatment of a strongly suspected tension pneumothorax. Lung-ultrasound consensus update; Resuscitation guidance.

Pitfall #6: “Pulse” Ultrasound Can Quietly Extend No-Flow Time

Doppler and color flow can look convincing during CPR. Compressions and movement can generate flow signals and motion artifact that mimic a real pulse. The usual failure is subtle:

“Let’s check one more time…”

That single sentence is how a clean 10-second pulse check becomes a 20-second pause.

The rule:

• Prepare the probe, view and focused question during compressions; appoint a timekeeper.
• For a pulse-check assessment, acquire only within the existing planned pause. Keep the total check to no more than 10 seconds; ultrasound gets no extra time.
• Save a brief clip, resume compressions promptly and review the recording while CPR continues. If the image or pulse is unclear, resume immediately.
• Time-box the ultrasound component tightly; this article’s 2–3-second cue is a conservative proposed workflow, not a validated guideline threshold or a separate pause allowance. AHA pause safeguards; CASA workflow study.

ROSC is a clinical picture, not a Doppler screenshot:

• ECG rhythm interpreted with evidence of perfusion
• An abrupt ETCO₂ rise, considered alongside ventilation, drugs and CPR quality
• Clinical signs of perfusion
• A spontaneous arterial pressure waveform, if an arterial line is present; compression-generated waves alone do not establish ROSC. AHA intra-arrest monitoring guidance.

Ultrasound may support a treatment decision, but should not alone establish ROSC or determine termination of resuscitation.

Advanced imaging does not remove these limits. TEE can show the heart during compressions, but requires trained operators and appropriate procedural safeguards. The 2026 EXECT-CPR trial did not establish a clinical-outcome benefit from TEE-guided compression-site adjustment; it was underpowered. Doppler research during compressions is also promising, but diagnostic accuracy against arterial-line pulsatility is not evidence of better survival or a reason to stop CPR on a flow signal alone. EXECT-CPR; Doppler study.

Pitfall #7: Delaying Proven Therapies

Ultrasound fails the patient when it delays:

• Defibrillation
• Chest compressions
• Epinephrine
• Airway correction
• Chest decompression

Hard rule:
If ultrasound delays a proven therapy, it has failed its purpose.

Pitfall #8: Scanning When You Should Not

Do not scan when:

• The team is chaotic
• There is no timekeeper
• The operator is inexperienced
• Findings will not change management

Sometimes the best ultrasound decision is not scanning.

How to Stay Safe

Before interpreting any arrest ultrasound, ask:

• Did imaging prolong the pause? If yes, stop scanning and resume compressions immediately.
• Is the image reliable and consistent with the clinical context? If no, defer interpretation or seek clarification while CPR continues.
• Does the finding identify an actionable reversible cause? A reliable image may appropriately change management, but it must not interrupt resuscitation or be used alone to terminate it.

Interpret ultrasound alongside the clinical assessment, without prolonging compression pauses. AHA 2025; RCUK 2025.

Closing Line

POCUS does not make decisions for you.
It amplifies the quality of the decisions you were already making.

What Comes Next (Part 3)

Ultrasound-guided decision pathways in cardiac arrest:

Continue with Part 3: ultrasound-guided decision pathways.

• PE
• Tamponade
• Hypovolemia/hemorrhage
• Airway and ventilation problems