Point of care protocol for diagnostic use of ultrasound in differentiating different types of shock in the ED.

Patients in shock have high mortality, and therefore, rapid diagnosis and intervention are crucial in making a difference in their lives. The RUSH Exam helps to differentiate different types of shock at bedside effectively, thereby facilitating timely intervention and treatment appropriate for each type of shock.

There are three parts to the RUSH exam using the standard US equipments available in the ED.

The first part is a focused echocardiography evaluating the heart in three different aspects:
1. The sac
2. The squeeze
3. The strain

Pericardial effusion: looking for significant pericardial effusions causing cardiac tamponade.

General rule of thumb, pericardial effusion in the setting of shock = cardiac tamponade. Requires immediate US guided pericardiocentesis!

LV contractility and dilatation, with visual estimation of EF: looking for wall hypomobility due to MI, structural lesions, and longstanding cardiomyopathies that may be the cause of cardiogenic shock.

It also gives us an idea about how much fluid the patient can handle!

*best looked at with parasternal long-/short-axis view.

RV:LV ratio greater than normal (0.6) or deflection of interventricular septum from right to left indicates right heart strain.

Possible (and most lethal) cause: large central PE.

Action plan: immediate anticoagulation+fibrinolytics in the setting of PE with hypotension +/-SOB or AMS (AHA 2011 guidelines)

I'd like to think of the second part of the RUSH exam in two smaller parts:

The Tank 1.0: vascular volume status,
The Tank 2.0: the lungs

IVC size and degree of collapse with inspiration.

The "Tank" is 'empty' with:
-IVC ->50% collapse
CVP
The "Tank" is 'full' with:
-IVC >2cm
-CVP >10cmH20; indicative of cardiogenic or obstructive shock

*Not applicable to patients on vasodilators, diuretics and ventilators with positive pressure.

**Try the M-Mode Doppler

FAST Scan +/- extended FAST:
looking for internal hemorrhage or fluid accumulation in the abdominal cavity as well as in the thoracic cavity.

If positive, this also requires immediate action!

Tension pneumothorax is thought to cause obstructive shock. Although CXR is a good diagnostic tool for tension pneumothorax when clinical presentation is questionable, the M-Mode Doppler on US is also easily available and therefore part of the RUSH exam to pick up on any air space between the two pleura.

Left: normal positive motion lung; "waves on the beach"
Right: pneumothorax with no "beach"

*Use the high-freq linear array probe at the highest point on the chest (where air will likely to show)

Pulmonary edema is often present in the setting of cardiogenic shock.

On US, it shows up as "Ultrasound-B lines" or "lung rockets".

*Use the phased-array transducer in anterolateral chest between 2nd and 5th rib spaces.

Finally the last part of the RUSH exam. This section of the exam involves carefully following the big vessels on both the arterial and venous sides, looking for any catastrophic vessel damage that may cause shock.

*Trace the aorta with a phased-array transducer or a curvilinear transducer. High-freq linear probe for the veins.

Looking for things like AAA and aortic dissection.

Looking for DVTs

All information and ultrasound pictures are from:
Perera P, Mailhot T, Riley D, Mandavia D. The RUSH exam: Rapid Ultrasound in SHock in the evaluation of the critically lll. Emerg Med Clin North Am. 2010;28(1):29-56, vii.

With supporting information from:
http://emcrit.org/rush-exam/original-rush-article/