What is new in critical care echocardiography?

Critical care echocardiography (CCE) is performed and interpreted by the intensivist at the bedside to help in the diagnostic work-up and to guide therapy for patients with acute circulatory and respiratory failure. Due to the statement of educational standards, the validation of echocardiography against alternative hemodynamic monitoring tools, and continuous technological improvement, CCE is increasingly being considered as an unparalleled technique to hemodynamically assess critically ill patients. Extremely active research in the field of CCE has resulted in recent improvements which warrant comment (Table 1). CCE provides unique morphological and functional information in real time to depict the hemodynamic profile of shock [1, 2]. The recent consensus on circulatory shock and hemodynamic monitoring of the European Society of Intensive Care Medicine suggests that CCE is the preferred modality to initially evaluate the type of shock as opposed to more invasive techniques. To provide adequate training of intensivists, international roundtables have recently detailed the theoretical knowledge and practical skills that should be mastered to achieve competence in both basic and advanced CCE. Basic CCE should be part of the initial training of all intensivists, whereas advanced CCE is an optional component of competency since it requires a more extensive and specific training [3]. Computerized simulation accelerates the learning curve of transesophageal echocardiography for the hemodynamic assessment of critically ill patients [4]. CCE helps to assess the fluid responsiveness and both the efficacy and tolerance of blood volume expansion in patients with shock, irrespective of their respiratory status [5]. A recent multicenter study prospectively assessed 540 ventilated patients with shock of any origin using transesophageal echocardiography and systematic passive leg raise to mimic a transient central blood volume expansion [6]. With the exception of the superior vena cava collapsibility index which was obtained in nearly all patients, dynamic indices proposed to predict fluid responsiveness were obtained in approximately 78% of patients. Respiratory variation of left ventricular outflow tract Doppler maximal velocity was the most sensitive index, whereas the superior vena cava collapsibility index was the most specific to predict fluid responsiveness. Due to a large range of uninformative values of dynamic indices, authors proposed using high yet specific threshold values to accurately predict fluid responsiveness in patients for whom inefficient fluid loading would be detrimental (e.g., acute respiratory distress syndrome), whereas a more liberal approach could be used in the remaining patients with repeated CCE assessment of both efficacy and tolerance of serial minifluid loadings [6]. Importantly, CCE solely can ascribe the respiratory variation of pulse pressure or stroke volume (pulse contour method) to a right ventricular failure (Fig. 1), and accordingly avoid a false-positive diagnosis of fluid responsiveness [7]. CCE plays a major role in the diagnostic work-up of patients presenting with acute respiratory failure [8]. In assessing left ventricular diastolic properties and filling pressure, CCE accurately identifies cardiogenic edema or weaning pulmonary edema, and potentially associated cardiopathy. According to the Berlin definition of the acute respiratory distress syndrome, echocardiography is recommended to exclude hydrostatic pulmonary edema. Since the prevalence of acute cor pulmonale in this clinical setting reaches 22%, a risk score has been proposed to select patients who should undergo CCE [9]. In addition, transesophageal echocardiography is the reference diagnostic modality to identify potentially associated patent foramen ovale [8]. Used as either a focused cardiac evaluation at the basic level or a comprehensive hemodynamic assessment modality at the advanced level, CCE yields valuable information which helps determine the mechanism of Correspondence: [email protected] Medical-surgical intensive care unit, Dupuytren Teaching hospital, Limoges, France INSERM Clinical Investigation Center 1435, Dupuytren Teaching hospital, Limoges, France Full list of author information is available at the end of the article