Hemodynamic Collapse in the ICU: How to Use POCUS and Echo to Differentiate Shock

In the ICU, hemodynamic collapse requires rapid differentiation to avoid giving the wrong treatment (e.g., giving fluids to a patient in cardiogenic shock). Point-of-Care Ultrasound (POCUS) and echocardiography provide a non-invasive “window” into the patient’s physiology, allowing you to categorize shock into four main types: Hypovolemic, Cardiogenic, Obstructive, and Distributive.

The most common framework for this is the RUSH Protocol (Rapid Ultrasound for Shock and Hypotension), which systematically evaluates the Pump, the Tank, and the Pipes.

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1. The Pump: Cardiac Assessment

Using the Parasternal Long Axis (PLAX), Parasternal Short Axis (PSAX), and Apical 4-Chamber (A4C) views, you can assess the heart’s function and structure.

Shock Type	POCUS Findings (Heart)	Specific Signs
Hypovolemic	Hyperdynamic (vigorous contraction)	“Kissing papillary muscles” (LV walls touch in systole)
Cardiogenic	Hypodynamic (poor LV/RV contractility)	Dilated LV, poor mitral valve excursion (EPSS > 7mm)
Obstructive	RV Strain / Tamponade signs	D-sign (septal flattening), RV > LV size, Pericardial effusion
Distributive	Often hyperdynamic (early)	Can show late-stage sepsis-induced cardiomyopathy

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M-Mode echocardiogram showing EPSS or E point septal separation of the mitral valve echo. E point is the maximum opening motion of the anterior mitral leaflet. Normally it will reach almost up to the septum, with only minimal separation. Increased EPSS means mitral valve opening excursions are low due to low cardiac output state. This M-Mode also shows poor left ventricular contraction as evidenced by little movement of IVS towards LVPW. B hump in the AML motion indicates high left ventricular end diastolic pressure in heart failure. Pericardial effusion marked as PE appears as echo free space around the heart.

2. The Tank: Volume and Effusions

The “Tank” assessment looks at the Inferior Vena Cava (IVC) for volume status and “leaks” (free fluid).

• The IVC:
  • Flat IVC (<1.5 cm) + High Collapsibility: Suggests Hypovolemic or Distributive shock.
  • Distended IVC (>2.1 cm) + No Collapse: Suggests Cardiogenic or Obstructive (tamponade/pulmonary embolism) shock.
• The “Leaks” (E-FAST – Extended Focused Assessment with Sonography in Trauma):
  • Check Morrison’s Pouch, the Splenorenal space, and the Pelvis for free fluid (hemorrhage).
  • Lungs: Check for B-lines (pulmonary edema, typical of Cardiogenic shock) vs. Lung Sliding (absent in pneumothorax—a cause of Obstructive shock).

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3. The Pipes: Great Vessels

This step identifies catastrophic vascular failures.

• Aorta: Scan for Abdominal Aortic Aneurysm (AAA) or intimal flaps (Aortic Dissection).
• Veins: Perform a two-point compression scan (femoral and popliteal veins) to look for DVT, which increases the probability of Pulmonary Embolism (Obstructive shock). In the image, obstructed vein having thrombus, with no flow on Colour Doppler is seen.

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Summary of Findings by Shock Type

Feature	Hypovolemic	Cardiogenic	Obstructive (Pulmonary Embolism/ Tamponade)	Distributive (Sepsis)
LV Function	Hyperdynamic	Hypodynamic	Normal/Hyperdynamic	Hyperdynamic (early)
IVC Size	Small/Flat	Large/Fixed	Large/Fixed	Small/Flat
Lungs	Clear (A-lines)	B-lines (Edema)	Clear or Pneumothorax	Clear or Focal B-lines
Other	Free fluid in belly	Dilated LV	RV Strain / Effusion	Source of infection

Diagnostic “Red Flags” to Watch For:

• McConnell’s Sign: Akinesia of the RV mid-free wall with sparing of the apex (in acute pulmonary embolism).
• RA/RV Diastolic Collapse: The “shuddering” of the right chambers during diastole, indicating cardiac tamponade.
• EPSS (E-Point Septal Separation): Measure the distance between the mitral valve and the septum in PLAX. If >7mm, the LV function is likely severely reduced.