What is the role of ultrasound in diagnosing and managing cardiac arrest in an adult or pediatric patient with potential reversible causes?

Role of Ultrasound in Cardiac Arrest

Ultrasound may be used during cardiac arrest as an additional diagnostic tool to identify reversible causes, but only if performed by trained personnel without interrupting chest compressions for more than 10 seconds. 1

Primary Recommendation

The 2020 International Consensus guidelines suggest AGAINST using point-of-care echocardiography for prognostication during CPR (weak recommendation, very low-certainty evidence), but support its use for identifying reversible causes when it does not interfere with high-quality CPR. 1

The critical distinction here is between two uses: prognostication (predicting outcomes based on cardiac motion) versus diagnosis (identifying treatable causes). The evidence strongly discourages the former while cautiously supporting the latter. 1

When to Use Ultrasound During Cardiac Arrest

Diagnostic Applications (Supported)

Ultrasound should be considered specifically to identify the "4 H's and 4 T's" reversible causes: 1, 2

• Cardiac tamponade - Point-of-care ultrasound demonstrates 100% sensitivity and specificity when performed by experienced personnel 2
• Massive pulmonary embolism - 100% sensitivity, 97% specificity 2
• Severe hypovolemia - Assess IVC collapsibility and cardiac chamber size 3
• Tension pneumothorax - Lung ultrasound can rapidly exclude this diagnosis 4
• Myocardial infarction - 86% sensitivity, 94% specificity 2

Critical Implementation Requirements

To minimize harm from interrupting chest compressions, ultrasound must be: 1

• Performed by an experienced operator trained in resuscitation ultrasound 1
• Completed during pulse checks only (≤10 second pauses) 1, 5
• Used when there is clinical suspicion for a specific reversible cause 2
• Integrated into the resuscitation protocol without delaying standard ACLS 1

What NOT to Use Ultrasound For

Prognostication (Not Recommended)

The presence or absence of cardiac motion on ultrasound should NOT be used to predict outcomes or guide termination of resuscitation efforts. 1

The 2020 guidelines explicitly recommend against this practice because: 1

• Very low certainty of evidence across all outcomes
• High risk of bias in observational studies
• Substantial variability in how "cardiac motion" is defined and measured
• No randomized trials demonstrating benefit

While absence of cardiac motion was highly predictive of death in older studies (only 2 of 218 patients with cardiac standstill achieved ROSC), this does not justify using it to terminate resuscitation, particularly in pediatric patients where myocardial stunning may be reversible. 1

Pediatric Considerations

In children, bedside cardiac ultrasound may identify reversible causes (pericardial effusion, tamponade, severe hypovolemia, chamber enlargement) but is INSUFFICIENT alone to diagnose irreversible cardiac arrest. 1

The pediatric heart has unique recovery potential: 1

• Severe myocardial stunning can persist for days after ECMO cannulation yet fully recover
• Cardiac arrest in children is primarily respiratory in origin, making rapid oxygen restoration potentially more effective
• An initially akinetic pediatric heart may ultimately be recoverable

Practical Protocol Approach

The CAUSE protocol (Cardiac Arrest Ultra-Sound Exam) provides a structured approach: 3

1. Cardiac view - Assess for tamponade, wall motion, chamber size
2. Aorta - Evaluate for abdominal aortic aneurysm rupture
3. Ultrasound lung - Rule out pneumothorax
4. Severe hypovolemia - IVC assessment, free fluid
5. Embolism - Right heart strain, DVT

Each examination should take less than 10 seconds and be performed during rhythm checks. 5

Equipment Requirements

Use a narrow, portable machine with: 4

• Fast start-on time
• Simple keyboard with essential buttons only
• Universal microconvex probe capable of multiple applications
• Basic gray-scale imaging without unnecessary filtering or harmonics

Common Pitfalls to Avoid

Critical errors that worsen outcomes: 1, 2

• Prolonged interruptions in chest compressions - This is the primary harm and negates any diagnostic benefit 1
• Using ultrasound to terminate resuscitation - Absence of cardiac motion alone is insufficient justification 1
• Attempting ultrasound without adequate training - Inexperienced operators cause longer pauses and misinterpretation 1
• Delaying definitive treatments - Ultrasound should never delay defibrillation, epinephrine, or other ACLS interventions 1
• Misinterpreting findings in pediatric patients - Apparent cardiac standstill may be reversible in children 1

Evidence Quality and Limitations

The evidence base remains problematic: 1, 6

• No randomized controlled trials demonstrate improved survival with ultrasound use during CPR
• All studies have high risk of bias from selection bias, lack of blinding, and confounding
• Substantial heterogeneity prevents meta-analysis
• Very low certainty of evidence across all outcomes (GRADE methodology)

The 2015 RCT of 100 patients showed no difference in ROSC (34% ultrasound group vs 28% control, p=0.52), though it was underpowered to detect clinically meaningful differences. 1

Post-ROSC Applications

After return of spontaneous circulation, ultrasound has clearer utility: 2, 7

• Assess cardiac function and guide hemodynamic support
• Evaluate volume status and response to interventions
• Identify ongoing reversible causes requiring treatment
• Monitor for complications in post-cardiac arrest syndrome

In this setting, the risk-benefit calculation shifts favorably since chest compressions are no longer needed. 7