This chapter reviews an important component of critical care ultrasonography (CCUS), which is basic critical care echocardiography (CCE). For purpose of the discussion, the term goal-directed echocardiography (GDE) and basic CCE are used interchangeably. They refer to a limited cardiac ultrasonography examination performed by the intensivist at bedside of the patient with hemodynamic failure in order to establish diagnosis and guide management of the shock state. The examination differs from cardiology-type echocardiography in the intensivist all aspects of the examination. Image acquisition, image interpretation, and application of the results are performed by the bedside clinician who is charge of the case. There is no delay in performance or interpretation of the study, nor is there any problem with clinical disassociation that occurs when the ultrasonographer is not directly involved with management of the case. GDE may be repeated as often as required by the clinical situation in order to track the evolution of disease and response to therapy.
The GDE Examination
The ACCP/SRLF Statement of competence in CCUS defines GDE with transthoracic echocardiography (TTE) as constituting five views:1 the parasternal long- and short-axis views, the apical four-chamber view, the subcostal long-axis four-chamber view, and the inferior vena cava (IVC) longitudinal view (Case 6-1). Color Doppler may be utilized in order to screen for significant valve dysfunction. The technique of obtaining these key views is reviewed in the chapter on TTE (ch006 ). It may be difficult to obtain all five views in the critically ill patient, and so it is important to attempt all five in every patient. For example, patients on ventilatory support who are hyperinflated due to PEEP effect or obstructive airway disease may have inadequate parasternal and apical four-chamber views, and yet have a good quality subcostal view. If the IVC is not visible through an anterior sagittal approach, the examiner may need to scan from a lateral approach. A key aspect of GDE is its simplicity. The examination takes a only few minutes to perform, so that the intensivist may perform a rapid evaluation of shock state and immediately integrate the results into other key elements clinical evaluation: the history, the physical examination, and the laboratory analysis. There is no alternative method of assessing cardiac anatomy and function in the intensive care unit (ICU), given clinical reality of the ICU. For the frontline intensivist, mastery of GDE is an essential skill for the evaluation of the patient in shock.
Case 6-1 Hypotension and Urosepsis
Goal-directed echocardiography (GDE) was performed on a patient who presented with hypotension and urosepsis. By definition, GDE must include the parasternal long-axis view, the parasternal short-axis view, the apical four-chamber view, subcostal long-axis view, and the inferior vena cava view. Videos 6-1A through E show a normal GDE. Based on these results, the critical care team categorized the shock state as distributive without evidence of obstructive, cardiogenic, or hypovolemic shock. Phenylephrine was the primary pressor agent given for vasoplegia of sepsis. As the IVC was greater than 2.5 cm in diameter without much respiratory variation, no further volume resuscitation was indicated. A follow-up GDE was performed which is shown in Case 6-7. The heart is not completely visualized on the subcostal view due to shadowing from bowel gas. There is a possible echogenic structure adjacent to the right atrial free wall on the apical four-chamber view that is not visible in other views. This would warrant referral for an advanced echocardiography examination.
The GDE examination may also be performed with transesophageal echocardiography (TEE). A typical set of images may be obtained from the midesophageal four-chamber view at 0°, the midesophageal three-chamber view at 120°, and the transgastric short-axis view at 0°. The superior vena cava view is preferred over the IVC view with TEE due to ease of use and its value at determination of preload sensitivity. The technique of obtaining these key views is reviewed in the chapter on TTE (Chapter 7). Though it is counter intuitive, skill at GDE using TEE may be easier to achieve compared to TTE; as the transducer movement is restricted to the esophagus, and the image planes are stereotypical. The image set that defines GDE with TEE not as fully established as that for TTE and several variations have been described, the latest of which can be performed with a miniaturized TEE probe that can be left in place for up to 72 h, allowing for repeated limited examinations. With this device, the GDE examination includes the SVC short-axis view, the midesophageal four-chamber view, and the transgastric view.
The use of TEE for GDE is not a mandatory component of competence in of CCE for the reason that the technology is not yet widely available in many ICUs;2 so that in North America and in many European countries, it is not common for intensivists to have access to TEE capability. Just as TTE is now much more widely available than a few years ago, it is likely that TEE will gradually become a standard ICU tool both for GDE and advanced CCE examinations.
Training in GDE
One question to ask is whether noncardiologists can be trained to perform GDE. The answer is unequivocally affirmative. Numerous studies have shown that noncardiologists at various levels of training can achieve mastery of GDE.3–12 The American Society of Echocardiography has issued a position paper supporting GDE for use by emergency medicine physicians the principle of which applies equally well to intensivists.13 Proficiency in GDE may be achieved by any interested intensivist providing the training program is well designed. Some recommendations regarding training in GDE are summarized in the chapter on training in CCUS of this textbook (Chapter 3). As with other aspects of CCUS, training in GDE requires the integration of training in image acquisition and image interpretation, with the cognitive elements of the field. Required cognitive elements that allow the clinician to make clinical decisions are summarized in Tables 6-1 and 6-2.
|Echocardiography: Required Cognitive Skills in Image Interpretation|
|Global LV size and systolic function|
|Homogeneous/heterogeneous LV contraction pattern|
|Global RV size and systolic function|
|Assessment for pericardial fluid/tamponade|
|IVC size and respiratory variation|
|Basic color Doppler assessment for severe valvular regurgitation|
|Cognitive Skills in Recognition of Clinical Syndromes|
|Clinical Syndromes||Echocardiographic Findings|
|Severe hypovolemia||Small, hyperdynamic ventricles|
|Small IVC with wide respiratory variations|
|LV failure||Global LV systolic dysfunction|
|Heterogeneous contractility pattern suggestive of myocardial ischemia|
|LV cavity dilatation suggestive of chronic cardiac disease|
|RV failure||Acute cor pulmonale: RV dilatation and paradoxical septal motiona|
|Isolated RV dilatation suggestive of RV infarct|
|Associated findings: dilated, noncollapsible IVC|
|Tamponade||Pericardial effusion (regardless of size)b|
|Right atrial/RV diastolic collapse|
|Associated findings: dilated, noncollapsible IVC|
|Acute massive left sided valvular regurgitation||Normal LV cavity size (acute valvulopathy)|
|Normal/hyperdynamic LV systolic function (LV volume overload)|
|Massive color Doppler regurgitant flowc|
|During resuscitation||Tamponade or acute cor pulmonale (from massive pulmonary embolism)|
|LV systolic function (cardiac standstill vs. severely depressed vs. hyperdynamic)|
|Global LV systolic dysfunction|
|After successful resuscitation||Heterogeneous contractility pattern suggestive of myocardial ischemia|
In terms of training program design for TTE, Manasia et al. reported that with 10 h of training, intensivists were able to perform GDE with results that were clinically relevant and that had strong correlation with cardiology performed studies.14 Vignon et al. have described a program for training in GDE and concluded that 12-h training program that combined didactics, interactive clinical cases, and supervised hands-on training sessions for noncardiology residents was effective for reaching competence in basic CCE.15,16 Regarding TEE, Benjamin et al. found that intensivists could perform GDE with results similar to cardiology performed TEE following an average of 10 supervised training studies.17
While is clear that intensivists can become skilled at GDE, it is important that the training program be well designed. The intensivist makes major clinical decisions that are predicated on the results of the GDE that may spell the difference between the life and death of the patient. The number of studies and duration of study may have uncertain relationship to the skill of the clinician in GDE. One means of assuring competence following training is to utilize rigorous competency based testing as a routine part of training program design.18
Clinical Applications of GDE
GDE should be a standard part of the assessment of the patient with hemodynamic failure. It is always combined with the history, the physical examination, and the laboratory assessment. It allows the intensivist for an immediate qualitative assessment of cardiac anatomy and function and so has effect on bedside management of the case in a variety of ways:
Identification of an imminently life-threatening disease process: The use of GDE allows the intensivist to identify an imminently life-threatening process where delay in diagnosis may result in the death of the patient and where urgent intervention may be lifesaving. Such situations include severe pericardial tamponade, major valve failure, massive pulmonary embolism, and the patient who is in severe shock while on inappropriate inotropic support with end systolic effacement pattern. Though uncommon, each of these has a specific therapeutic response that may be lifesaving (Cases 6-2 through 6-5).
Categorization of shock state and selection of initial management strategy: The use of GDE allows the intensivist to rapidly categorize the hemodynamic failure. With the five standard views, the frontline intensivist to classifies the shock as cardiogenic, obstructive, hypovolemic, or distributive in pattern (Case 6-6). This categorization leads to logical selection of management strategy as well as search for etiology of abnormality. For example, the finding of normal cardiac function without evidence of preload sensitivity by analysis of IVC dynamics suggests that the patient has a distributive shock state. Further volume resuscitation and inotropic support are not indicated; vasopressors are the preferred agent to maintain blood pressure. The presence of severe left ventricular dysfunction with a large IVC suggests that inotropes are the indicated medication for the shock state. The presence of acute cor pulmonale pattern with shock results in immediate search for the cause of the right ventricular failure.
Evolution of disease and response to therapy: The use of repeated serial GDE allows the intensivist to follow the evolution of critical illness and response to therapy. The nature of critical illness is that it is a dynamic process, as is response to therapy (Case 6-7). The standard cardiology echocardiography approach does not typically include serial studies in close succession. This approach is routine with GDE. Early in the course of illness, GDE can easily be performed several times per day. As the patient becomes more stable, the frequency is reduced according to clinical requirements.
Identification of coexisting diagnosis: The use of GDE allows the intensivist to identify the presence of coexisting diagnosis that complicate the management of the primary process. This situation commonly occurs in the older patient or the patient with complex medical presentation. A typical example is the elderly patient with sepsis presentation who on GDE has evidence of severe aortic stenosis and severe left ventricular failure (Case 6-8). Though sepsis may be predominant cause of the shock state, early identification of the coexisting processes allows the intensivist to modify management strategy.