(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.
Most harm from ultrasound in CPR does not come from poor image acquisition.
It comes from misinterpretation, over-trust, and 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.
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 you are unsure, treat it as no meaningful contraction and continue CPR.
- Motion ≠ perfusion.
Pitfall #3: Cardiac Standstill Misused as a Stop Rule
Cardiac standstill is strongly associated with mortality.
It is not absolute.
A small number of patients with sonographic standstill still achieve ROSC.
Key rule:
- Standstill informs prognosis, not permission.
- 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
ERC warns against diagnosing PE based on RV dilation alone.
A safer approach: the PE confidence ladder
PE becomes more likely when you have:
- Compatible story and risk factors
- Early RV strain pattern
- Support during compressions (e.g., positive proximal DVT)
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:
- Lung ultrasound rules out pneumothorax better than it rules it in.
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:
- Set up during compressions (probe on femoral or carotid; optimize view/Doppler).
- Interpret only during the planned pulse check.
- Time-box it (2–3 seconds).
- If unclear → hands back on chest immediately.
ROSC is a clinical picture, not a Doppler screenshot:
- Rhythm on ECG
- ETCO₂ trend
- Signs of perfusion
- Arterial line waveform (if available)
Ultrasound can support that assessment—but it should never be the deciding vote.
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 this prolong the pause?
- Does this fit the clinical story?
- Would I make the same decision without this image?
If the answer is “no,” pause the interpretation—not CPR.
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:
- PE
- Tamponade
- Hypovolemia/hemorrhage
- Airway and ventilation problems
