Appréciation non invasive de la pression veineuse centrale par la mesure échographique du calibre de la veine cave inférieure en réanimation

Can non-invasive ventilation modify central venous pressure? Comparison between invasive measurement and ultrasonographic evaluation

Central venous pressure (CVP) is primarily measured to assess intravascular volume status and heart preload. In clinical practice, the measuring device most commonly used in emergency departments and intensive care units, is an electronic transducer that interconnects a central venous catheter (CVC) with a monitoring system. Non-invasive ventilation (NIV) consists in a breathing support that supplies a positive pressure in airways through a mask or a cask though not using an endotracheal prosthesis. In emergency settings, non-invasive ultrasonography evaluation of CVP, and hence of intravascular volume status entail the measurement by a subxiphoid approach of inferior vena cava diameter and its variations in relation to respiratory activity. In the literature, there are many studies analyzing the ability to estimate CVP through ultrasonography, rating inspiratory and expiratory vena cava diameters and their ratio, defined as inferior vena cava collapsibility index (IVC-CI). At the same time, the effects of invasive mechanical ventilation on blood volume and the correlation during ventilation between hemodynamic invasive measurement of CVP and inferior vena cava diameters have already been demonstrated. Nevertheless, there are no available data regarding the hemodynamic effects of NIV and the potential correlations during this kind of ventilation between invasive and non-invasive CVP measurements. Therefore, this study aims to understand whether there exists or not an interrelationship between the values of CVP assessed invasively through a CVC and non-invasively through the IVC-CI in patients with severe respiratory distress, and above all to evaluate if these means of assessment can be influenced using NIV.

Echocardiography in the sepsis syndromes

Purpose of the review

Non-invasiveness and instantaneous diagnostic capability are prominent features of the use of echocardiography in critical care. Sepsis and septic shock represent complex situations where early hemodynamic assessment and support are among the keys to therapeutic success. In this review, we discuss the range of applications of echocardiography in the management of the septic patient, and propose an echocardiography-based goal-oriented hemodynamic approach to septic shock.

Recent findings

Echocardiography can play a key role in the critical septic patient management, by excluding cardiac causes for sepsis, and mostly by guiding hemodynamic management of those patients in whom sepsis reaches such a severity to jeopardize cardiovascular function. In recent years, there have been both increasing evidence and diffusion of the use of echocardiography as monitoring tool in the patients with hemodynamic compromise. Also thanks to echocardiography, the features of the well-known sepsis-related myocardial dysfunction have been better characterized. Furthermore, many of the recent echocardiographic indices of volume responsiveness have been validated in populations of septic shock patients.

Conclusion

Although not proven yet in terms of patient outcome, echocardiography can be regarded as an ideal monitoring tool in the septic patient, as it allows (a) first line differential diagnosis of shock and early recognition of sepsis-related myocardial dysfunction; (b) detection of pre-existing cardiac pathology, that yields precious information in septic shock management; (c) comprehensive hemodynamic monitoring through a systematic approach based on repeated bedside assessment; (d) integration with other monitoring devices; and (e) screening for cardiac source of sepsis.

Relation of tricuspid annular displacement and tissue Doppler imaging velocities with duration of weaning in mechanically ventilated patients with acute pulmonary edema

BACKGROUND

Liberation from the ventilator is a difficult task, whereas early echocardiographic indices of weaning readiness are still lacking. The aim of this study was to test whether tricuspid annular plane systolic excursion (TAPSE) and right ventricular (RV) systolic (Sm) and diastolic (Em & Am) tissue Doppler imaging (TDI) velocities are related with duration of weaning in mechanically ventilated patients with acute respiratory failure due to acute pulmonary edema (APE).

METHODS

Detailed quantification of left and right ventricular systolic and diastolic function was performed at admission to the Intensive Care Unit by Doppler echocardiography, in a cohort of 32 mechanically ventilated patients with APE. TAPSE and RV TDI velocities were compared between patients with and without prolonged weaning (> or = or < 7 days from the first weaning trial respectively), whereas their association with duration of ventilation and left ventricular (LV) echo-derived indices was tested with multivariate linear and logistic regression analysis.

RESULTS

Patients with prolonged weaning (n = 12) had decreased TAPSE (14.59 +/- 1.56 vs 19.13 +/- 2.59 mm), Sm (8.68 +/- 0.94 vs 11.62 +/- 1.77 cm/sec) and Em/Am ratio (0.98 +/- 0.80 vs 2.62 +/- 0.67, p <0.001 for all comparisons) and increased Epsilon/e' (11.31 +/- 1.02 vs 8.98 +/- 1.70, p <0.001) compared with subjects without prolonged weaning (n = 20). Logistic regression analysis revealed that TAPSE (R2 = 0.53, beta slope = 0.76, p < 0.001), Sm (R2 = 0.52, beta = 0.75, p < 0.001) and Em/Am (R2 = 0.57, beta = 0.32, p < 0.001) can predict length of weaning > or = 7 days. The above measures were also proven to correlate significantly with Epsilon/e' (r = -0.83 for TAPSE, r = -0.87 for Sm and r = -0.79 for Em/Am, p < 0.001 for all comparisons).

CONCLUSIONS

We suggest that in mechanically ventilated patients with APE, low TAPSE and RV TDI velocities upon admission are associated with delayed liberation from mechanical ventilation, probably due to more severe LV heart failure.

Focused Echocardiography in Life Support: The Subcostal Window : What the Surgeon Should Know for Critical Care Applications

CONTEXT

Focused echocardiography evaluation in life support (FEEL) for emergency and critical caremedicine is an innovative approach to introducing limited-in-scope echocardiography in a timely fashion into periresuscitation care. FEEL is an advanced life support-conformed concept and a simple procedure that can be readily used in shock roomor pre-hospital scenarios as an extension of focused abdominal sonography for trauma (FAST). The subcostal window plays a pivotal role in this context, because it can easilybe applied inthesupine position, and is usually better than other windows in patients with mechanical ventilation or during resuscitation maneuvers. Most information can be obtained at a glance.

AIM

As the FAST exam was not developed for implementation in resuscitation or cardiac arrest procedures, herewedescribe an accurate and easymethod that allows non-cardiologists to add FEEL to the FAST exam. As a result, it conforms to actual resuscitation guidelines. To perform the FEEL procedure and the subcostal window, a specific training seems to bemandatory. The aim of this paper is to set special emphasis on the use of the subcostal window.

Echocardiography practice, training and accreditation in the intensive care: document for the World Interactive Network Focused on Critical Ultrasound (WINFOCUS)

Echocardiography is increasingly used in the management of the critically ill patient as a non-invasive diagnostic and monitoring tool. Whilst in few countries specialized national training schemes for intensive care unit (ICU) echocardiography have been developed, specific guidelines for ICU physicians wishing to incorporate echocardiography into their clinical practice are lacking. Further, existing echocardiography accreditation does not reflect the requirements of the ICU practitioner. The WINFOCUS (World Interactive Network Focused On Critical UltraSound) ECHO-ICU Group drew up a document aimed at providing guidance to individual physicians, trainers and the relevant societies of the requirements for the development of skills in echocardiography in the ICU setting. The document is based on recommendations published by the Royal College of Radiologists, British Society of Echocardiography, European Association of Echocardiography and American Society of Echocardiography, together with international input from established practitioners of ICU echocardiography. The recommendations contained in this document are concerned with theoretical basis of ultrasonography, the practical aspects of building an ICU-based echocardiography service as well as the key components of standard adult TTE and TEE studies to be performed on the ICU. Specific issues regarding echocardiography in different ICU clinical scenarios are then described. Obtaining competence in ICU echocardiography may be achieved in different ways - either through completion of an appropriate fellowship/training scheme, or, where not available, via a staged approach designed to train the practitioner to a level at which they can achieve accreditation. Here, peri-resuscitation focused echocardiography represents the entry level--obtainable through established courses followed by mentored practice. Next, a competence-based modular training programme is proposed: theoretical elements delivered through blended-learning and practical elements acquired in parallel through proctored practice. These all linked with existing national/international echocardiography courses. When completed, it is anticipated that the practitioner will have performed the prerequisite number of studies, and achieved the competency to undertake accreditation (leading to Level 2 competence) via a recognized National or European examination and provide the appropriate required evidence of competency (logbook). Thus, even where appropriate fellowships are not available, with support from the relevant echocardiography bodies, training and subsequently accreditation in ICU echocardiography becomes achievable within the existing framework of current critical care and cardiological practice, and is adaptable to each countrie's needs.

Correlation between measured inferior vena cava diameter and right atrial pressure depends on the echocardiographic method used in patients who are mechanically ventilated

In patients who are mechanically ventilated, the correlation between inferior vena cava diameter (IVCD) measurements and mean right atrial pressure (RAP) varies in the literature. The purpose of this study was to test if the correlation between IVCD and RAP measurement in patients who are critically ill depends on the transthoracic echocardiography (TTE) methodology used. Twenty patients who were critically ill, sedated, and required respiratory support were prospectively studied by TTE during mechanical ventilation in a controlled mode. The TTE measures of IVCD were made, using methods previously cited. First, IVCD was measured at end-expiration and end-diastole, with ECG synchronization, using the M-mode, on short-axis view 2 cm below the right atrium. Second, IVCD was assessed at end-expiration, without ECG synchronization, using the 2-dimensional long-axis view at the same location. RAP was measured simultaneously by using a central venous catheter positioned in the superior vena cava. All measurements were taken in the supine position. IVCD at end-expiration and end-diastole, with ECG synchronization, using the M-mode, and IVCD at end-expiration, without ECG synchronization, using the 2-dimensional long-axis view, correlate linearly with RAP (0.81, P <.0001 and 0.71, P =.0004). Mean bias between the 2 TTE methods (Bland-Altman analysis) was 1.6 mm (SD +/- 2.03 mm). In conclusion, this study confirms that variation of correlation between TTE IVCD measurement and RAP depends on the ultrasonographic methodology used and the timing of measurement during the cardiac cycle. IVCD at end-expiration and end-diastole, with ECG synchronization, using the M-mode (IVCD-MM) correlates more satisfactory with RAP than with IVCD at end-expiration, without ECG synchronization, using the 2-dimensional long-axis view, in patients during mechanical ventilation.