Abstract
Urgent cardiac ultrasound examination in the critical care setting is clinically useful. Application of goal-directed echocardiography in this setting is quite distinct from typical exploratory diagnostic comprehensive echocardiography, because the urgent critical care setting mandates a goal-directed approach. Goal-directed echocardiography most frequently aims to rapidly identify and differentiate the cause(s) of hemodynamic instability and/or the cause(s) of acute respiratory failure. Accordingly, this paper highlights 1) indications, 2) an easily memorized differential diagnostic framework for goal-directed echocardiography, 3) clinical questions that must be asked and answered, 4) practical issues to allow optimal image capture, 5) primary echocardiographic views, 6) key issues addressed in each view, and 7) interpretation of findings within the differential diagnostic framework. The most frequent indications for goal-directed echocardiography include 1) the spectrum of hemodynamic instability, shock, and pulseless electrical activity arrest and 2) acute respiratory failure. The differential diagnostic categories for hemodynamic instability can be remembered using the mnemonic ‘SHOCK’ (for Septic, Hypovolemic, Obstructive, Cardiogenic, and (K) combinations/other kinds of shock). RESP-F (for exacerbation of chronic Respiratory disease, pulmonary Embolism, ST changes associated with cardiac or pericardial disease, Pneumonia, and heart Failure) can be used for acute respiratory failure. The goals of goal-directed echocardiography in the unstable patient are: assessing global ventricular systolic function, identifying marked right ventricular and left ventricular enlargement, assessing intravascular volume, and the presence of a pericardial effusion. In an urgent or emergent setting, it is recommended to go directly to the best view, which is frequently the subcostal or apical view. The five views are the subcostal four-chamber view, subcostal inferior vena cava view, parasternal long axis view, parasternal short axis view, and the apical four chamber view. Always interpret goal-directed echocardiographic findings in the context of clinically available hemodynamic information. When goal-directed echocardiography is insufficient or when additional abnormalities are appreciated, order a comprehensive echocardiogram. Goal-directed echocardiography and comprehensive echocardiography are not to be used in conflict with each other.
Highlights
Important guidelines have recently been published for the use of echocardiography in the critical care setting [1,2,3,4,5,6] and a large number of publications have investigated important aspects of echocardiography in critically ill patients, in particular the goal-directed approach [1,2,3,4,5,6]
We address a narrow aspect of these guidelines in detail, the use of goal-directed echocardiography to distinguish between differential diagnostic categories contributing to 1) hemodynamic instability, shock, and Pulseless electrical activity (PEA) arrest requiring immediate therapeutic decisions and interventions - the central indication for goal-directed echocardiography in the critical care setting - and 2) evaluation of acute respiratory failure
We provide a practical ‘primer’ approach while full discussion of all aspects of hemodynamic instability, shock, and PEA arrest is beyond the scope of this review [51]
Summary
Important guidelines have recently been published for the use of echocardiography in the critical care setting [1,2,3,4,5,6] and a large number of publications have investigated important aspects of echocardiography in critically ill patients, in particular the goal-directed approach [1,2,3,4,5,6]. Obstructive shock due to tamponade (evidence of hemodynamic compromise) may be observed in the A-4 view (Figure 3A) and the subcostal view (Figure 3B) These views will demonstrate a significant pericardial effusion (usually encompassing the heart) with right atrial wall or RV diastolic collapse. A patient presenting with a pulmonary embolism may demonstrate an enlarged RV, a hypokinetic lateral wall, and a hyperdynamic apex (McConnell’s sign) [61,62] The sensitivity of these findings to diagnose pulmonary embolism is 29% with goal-directed echocardiography and 51% with a comprehensive echocardiographic examination [2]. Features on goal-directed echocardiography that support the diagnosis of chronic COPD include evidence of RV hypertrophy and failure Acute respiratory causes, such as asthma and pneumonia, may have few specific findings on echocardiographic examination. Ventricular dysfunction leading to heart failure is important in the differential diagnosis of acute respiratory failure and may be manifested in a goal-directed echocardiographic examination by the same findings that characterize cardiogenic shock
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