Recently I coauthored an article about the bedside evaluation of shock using ultrasonography.  It's a reasonable article, albeit conventional.  Below is a summary of the key points.

Many textbooks recommend line-box algorithms for approaching a patient with shock, for example the ACES algorithm below.  These algorithms allow the operator to reach a diagnosis based on 2-3 decision nodes, without taking other information into account.

Although line-box algorithms are efficient, they fail when approaching complicated patients with multifactorial shock.  Additionally, they may encourage clinicians to focus on only a few features of the examination.  A more thorough approach is to perform a complete examination and then compare it to patterns expected for various types of shock (table below).  This may facilitate identification of patients with multifactorial shock, who will often defy simple categorization.

Clinical context is useful as well.  For example, hypovolemic and distributive shock may appear nearly identical on ultrasound (table above).  Other clinical findings may help make this distinction:

Finally, archival information can also be critical.  It is increasingly common to see patients with acute disease superimposed on chronic problems.  Many people are walking around with dilated right ventricles or severely reduced ejection fraction every day.  Evaluation of prior echocardiograms, EKGs, and CT scans may help determine if such features are acute or chronic (noting that chest or abdominal CT scans often reveal useful information about cardiac anatomy).

In conclusion, shock evaluation is hard work.  It starts with a thorough examination of the heart, lungs, and other relevant organs (e.g. DVT study if PE is suspected).  This must then be integrated with the clinical context including history, traditional examination, and any available diagnostic tests.  Finally, reviewing archival material can be crucial to confirm that pertinent abnormalities are truly part of an acute disease process.  Although this is a not easy, it will often result in prompt and unexpected diagnoses, which can be life-saving. 
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For the Farkas JD and Anawati MK.  Bedside Ultrasonography Evaluation of Shock.   Hospital Medicine Clinics 2015; 4(2).   PDF here.  

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