POCUS in Cardiac Arrest: Emergency Physician's Guide

Overview

• Rosen's Emergency Medicine, p. 3622
• Miller's Anesthesia 10e, p. 5033

The Golden Rule: CPR Integration

Preferred Views During Arrest

1. Subcostal (Subxiphoid) Four-Chamber View - PRIMARY VIEW

• Does not interfere with chest compressions
• Allows assessment of pericardial fluid, RV/LV size and function
• Is identical to the FAST cardiac window

Parasternal long-axis view - used as fallback if subcostal window is inadequate

Apical 4-chamber view showing enlarged RV - suspect PE or RV failure

2. Parasternal Long-Axis (PLAX) - FALLBACK

3. Supplemental Views (after compressions resume)

• Lung views (bilateral): absent lung sliding = tension pneumothorax
• IVC view: collapsibility index for volume status (filling assessment)
• Abdominal (in trauma): free fluid

The SHoC Protocol: The Four "Fs"

Diagnostic Applications: Identifying Reversible Causes (The Hs and Ts)

Cardiac Tamponade

• Findings: Anechoic fluid in pericardial space, diastolic RV collapse, plethoric (non-collapsible) IVC
• Pericardial effusions as small as 50 mL can cause tamponade in the acute setting
• If found, proceed to pericardiocentesis under ultrasound guidance
• Rosen's Emergency Medicine, p. 3623

Pulmonary Embolism (Massive)

• Findings: Dilated RV (RV:LV ratio >0.9 in A4C), McConnell's sign (RV free wall akinesis with preserved apex), "D" sign on parasternal short axis (septal flattening from elevated RV pressure), thrombus in right heart
• McConnell's sign is highly suggestive of PE but also seen in RV infarction

"D" sign on parasternal short axis - septal flattening from RV pressure overload, as seen in PE

Tension Pneumothorax

• Findings: Absent lung sliding (M-mode: "barcode" / "stratosphere" sign instead of "seashore" sign); lung point pathognomonic if found
• More sensitive than supine CXR, approaching CT sensitivity
• Rosen's Emergency Medicine, p. 3623

Hypovolemia

• Findings: Small, hyperdynamic LV ("kissing walls"), flat/collapsible IVC (<1 cm diameter)
• Guides empiric fluid resuscitation

Aortic Dissection / AAA Rupture

• Aortic dissection: linear echogenic intimal flap in the aorta or pericardial effusion + dilated aortic root (>4 cm)
• AAA: aortic diameter >3 cm (risk of rupture higher >4.5 cm), free peritoneal fluid in rupture
• Sensitivity 80-90%, specificity ~100% for dissection but should not be used to exclude it

Prognostic / Functional Assessment

True PEA vs Pseudo-PEA

• True PEA (cardiac standstill): No wall motion visible - universally poor prognosis
• Pseudo-PEA: Organized cardiac motion present despite no palpable pulse - patient may respond to aggressive resuscitation, treat as profound shock

Cardiac Standstill and ROSC Prediction

• Sensitivity of cardiac standstill for predicting absence of ROSC: 85.6% (95% CI 0.789-0.904)
• Specificity: 79.0% (95% CI 0.671-0.874)
• Diagnostic odds ratio: 22.6 (95% CI 12.45-41.0)
• AUC: 0.871 - indicating good diagnostic accuracy
• Breglia et al., J Emerg Med 2026 [PMID: 41610792]

PEA with Cardiac Activity - Prognosis

• ROSC prediction: sensitivity 0.86, specificity 0.64
• Survival to admission: sensitivity 0.89, specificity 0.73 (best AUC: 0.89)
• POCUS cardiac activity is useful as part of a multimodal approach to termination of resuscitation decisions
• Jian et al., Scand J Trauma Resusc Emerg Med 2025 [PMID: 39930527]

Important Caveat

Pulse Check: POCUS vs Manual Palpation

• POCUS had higher accuracy in all three studies reporting accuracy
• POCUS was faster in all five studies reporting speed
• Manual pulse palpation is known to be unreliable even by experienced providers
• Ko et al., J Emerg Med 2026 [PMID: 41274023]

CPR Quality Monitoring

• Adequate depth and rate of compressions (real-time LV compression)
• Mitral valve opening during release = adequate decompression
• Coronary perfusion pressure correlates (aortic relaxation pressure)
• TEE is increasingly preferred in periarrest settings as it avoids interrupting chest compressions entirely
• Miller's Anesthesia 10e, p. 5033

Transesophageal Echocardiography (TEE) in Arrest

• Continuous real-time imaging without interrupting CPR
• Superior image quality vs TTE in arrest (no chest wall obstruction)
• Direct LV compression assessment
• Identification of all reversible causes
• Especially useful when TTE windows are poor

Practical Algorithm Summary

CARDIAC ARREST
     |
     ▼
Rhythm/Pulse Check Pause (≤10 sec)
     |
     ├── Subcostal 4-chamber (preferred) or PLAX
     |       ├── Pericardial fluid? → Tamponade → Pericardiocentesis
     |       ├── RV dilation + McConnell's → PE → Lytics / ECPR
     |       ├── Cardiac standstill? → Poor prognosis (multimodal)
     |       └── Organized activity? → Pseudo-PEA → Aggressive Rx
     |
     ▼
Resume compressions → interpret + plan supplemental views
     |
     ├── Lung US: absent sliding → Tension PTX → Needle decompression
     ├── IVC: collapsed → Hypovolemia → Fluids
     └── Aorta: aneurysm/dissection, free fluid (trauma)

Key Points Summary

1. Timing is non-negotiable: POCUS during CPR must fit within the ≤10-second pulse check pause; all four major resuscitation guidelines require this
2. Subcostal view first - does not interfere with compressions; fallback to PLAX if inadequate
3. The SHoC Four Fs: Fluid (tamponade), Form (PE/RV strain), Function (standstill vs activity), Filling (IVC/volume)
4. Cardiac standstill predicts failure to achieve ROSC with sensitivity ~86%, specificity ~79% (2026 meta-analysis, n=3684); do not use in isolation to terminate resuscitation
5. Pseudo-PEA (organized activity despite no pulse) is actionable - treat as shock, not arrest
6. POCUS pulse check is faster and more accurate than manual palpation (2026 systematic review)
7. TEE avoids compression interruptions entirely and should be considered when available
8. Do not use POCUS to exclude aortic dissection or PE - sensitivity insufficient for rule-out
9. Reversible causes directly visualized: tamponade, massive PE, tension PTX, hypovolemia, aortic catastrophe