Chapter 9

Hemodynamic instability (acute and chronic) is a common problem in critically ill patients. Prolonged hypotension may lead to organ ischemia, dysfunction, and poor outcome.1 Conversely, rapid diagnosis and intervention may prevent this deterioration and improve outcome. Intensivists routinely look for common, immediately treatable problems; however, clinical examination alone may be insufficient to make these immediate therapeutic decisions. Clinical suspicion is the key to building a differential diagnosis and to the intelligent application of technology to aid in therapeutic decision-making. Echocardiography is one such technology, which may make a critical difference in the rapid diagnosis of both common and uncommon, but important, causes of unstable hemodynamics. Used in this way, echocardiography has been found to lead to a change in therapy in at least in a quarter of critically ill patients.2 The assessment of hemodynamics is commonly approached in terms of preload, afterload, and contractility, all of which may be aided by echocardiologic exam.

When assessing the unstable critically ill patient using echocardiography, the major causes of hemodynamic instability such as pulmonary embolism or pericardial tamponade may be quickly and reliably ruled out. This may be performed by experienced echocardiographers, intensivists, or emergency medicine physicians trained in one of the abbreviated echocardiographic examination protocols, for example, the Focus Assessed Transthoracic Echocardiography (FATE) protocol.3

Once major causes are ruled out, the next step in the patient assessment is to assess left ventricular (LV) volume status and function. The most important and commonly used method of assessing LV global and focal wall motion is by a qualitative assessment over multiple views. This method is extremely effective, rapid, and in agreement with nuclear scanning studies when done by an experienced echocardiographer. The result is both an assessment of regional wall motion and an overall assessment of LV function usually expressed in terms of an estimated ejection fraction (EF). Quantitative techniques of ventricular assessment allow for a more measurable and arguably less biased assessment of the ventricle. These techniques have their advantages and their limitations. It is incumbent upon the intensivist echocardiographer to be familiar with these advantages and limitations.

Transesophageal echocardiography is often considered superior to TTE in the ICU. Transthoracic echocardiography frequently provides poor image quality in postoperative patients due to mechanical ventilation (positive end-expiratory pressure [PEEP] >15 cm of H2O), inability to position the patient, lack of patient cooperation, chest wall edema and obstructed views due to wound dressings, chest tubes, drains, and an open chest or abdomen. In the critical care setting, TTE leads to a successful exam in 50% of attempts,4,5 in contrast to 90% with TEE.6 There are, however, challenges to the routine performance of TEE in the ICU. The TEE examination requires additional time and expertise when compared with the TTE exam. Insertion of the probe into the esophagus carries with it a risk of loss of the airway. Additionally, TTE carries with it a small but ...

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