Transoesophageal echocardiography in critically ill patients. A comprehensive approach:

A, B, C, D, echo: limited transthoracic echocardiogram is a useful tool to guide therapy for hypotension in the trauma bay--a pilot study

BACKGROUND

Limited transthoracic echocardiogram (LTTE) has been introduced as a technique to direct resuscitation in intensive care unit (ICU) patients. Our hypothesis is that LTTE can provide meaningful information to guide therapy for hypotension in the trauma bay.

METHODS

LTTE was performed on hypotensive patients in the trauma bay. Views obtained included parasternal long and short, apical, and subxyphoid. Results were reported regarding contractility (good vs. poor), fluid status (flat inferior vena cava [hypovolemia] vs. fat inferior vena cava [euvolemia]), and pericardial effusion (present vs. absent). Need for surgery, ICU admission, Focused Assessment with Sonography for Trauma examination results, and change in therapy as a consequence of LTTE findings were examined. Data were collected prospectively to evaluate the utility of this test.

RESULTS

A total of 148 LTTEs were performed in consecutive patients from January to December 2011. Mean age was 46 years. Admission diagnosis was 80% blunt trauma, 16% penetrating trauma, and 4% burn. Subxyphoid window was obtained in all patients. Parasternal and apical windows were obtained in 96.5% and 11%, respectively. Flat inferior vena cava was associated with an increased incidence of ICU admission (p < 0.0076) and therapeutic operation (p < 0.0001). Of the 148 patients, 27 (18%) had LTTE results indicating euvolemia. The diagnosis in these cases was head injury (n = 14), heart dysfunction (n = 5), spinal shock (n = 4), pulmonary embolism (n = 3), and stroke (n = 1). Of the patients, 121 had LTTE results indicating hypovolemia. Twenty-eight hypovolemic patients had a negative or inconclusive Focused Assessment with Sonography for Trauma examination finding (n = 18 penetrating, n = 10 blunt), with 60% having blood in the abdomen confirmed by surgical exploration or computed tomographic scan. Therapy was modified as a result of LTTE in 41% of cases. Strikingly, in patients older than 65 years, LTTE changed therapy in 96% of cases.

CONCLUSION

LTTE is a useful tool to guide therapy in hypotensive patients in the trauma bay.

LEVEL OF EVIDENCE

Diagnostic study, level III.

Influence of acute preload changes on mitral annulus velocity measured by tissue Doppler echocardiography in critically ill patients

AIM

The assessment of diastolic function remains difficult in critical care patients because of unstable preload conditions. Described as fairly insensitive to preload changes, tissue Doppler velocity measurement at the lateral mitral annulus (e' (lat) ) may help evaluate diastolic function. Our aim was to prospectively evaluate e' (lat) changes in relation to fluid expansion in critically ill patients.

METHODS

This prospective observational study was conducted in critically ill, mechanically ventilated, patients in sinus rhythm without previously known cardiac disease. Echocardiography was performed before and 1 hour after a fluid challenge (infusion of Gelofusine 500 ml in 30 minutes). Conventional pulsed wave Doppler indices of left ventricular diastolic function and tissue Doppler velocity lateral (e' (lat) ) and septal (e' (sept) ) mitral annulus velocity were measured, whereas hemodynamic data were simultaneously collected.

RESULTS

Twenty patients (age, 55 ± 15 years; Simplified Acute Physiology Score II, 45 ± 10) were enrolled. Systolic function was preserved in all patients. Cardiac index increased (p < 0.05), as did early diastolic mitral velocity (E wave) (p = 0.001), and e' (lat) and e' (sept) (p = 0.02) after fluid challenge.

CONCLUSIONS

This study confirms the preload dependence and limited clinical usefulness of most Doppler variables, such as e' (lat) , to evaluate diastolic function in intensive care unit patients. Indices, such as E/e', may be of interest in these cases.

[Echocardiography in the Intensive Care Unit]

The echocardiography can provide important and relevant information and the critically ill patient presents a challenge for the echocardiographer: from limitations in image acquisition to interpretation in the context of rapid physiological and intervention changes. The most frequent reason for requesting an echocardiogram in the ICU is probably to assess left ventricular function. In any case, information of direct relevance for clinical management can in relationship to abnormalities of structure and function can be obtained and used to estimate pulmonary arterial and venous pressures. It can help to investigate the consequences of myocardial ischemia, valvular dysfunction and pericardial disease and detect changes characteristic of specific conditions (e.g. sepsis, pulmonary thromboembolism), although this must be interpreted in the context of each individual patient. The echocardiography also can be used to monitor the therapeutic interventions. The applications of echocardiography in the critical care setting are reviewed, with special emphasis on the assessment of cardiac physiology.

A comparison of transoesophageal echocardiographic Doppler across the aortic valve and the thermodilution technique for estimating cardiac output

This study was undertaken in order to elucidate the differences between various planes of measurement and Doppler techniques (pulsed- vs. continuous-wave Doppler) across the aortic valve to estimate cardiac output. In 45 coronary artery bypass patients, cardiac output was measured each time using four different Doppler techniques (transverse and longitudinal plane, pulsed- and continuous-wave Doppler) and compared with the thermodilution technique. Measurements were performed after induction of anaesthesia and shortly after arrival in the intensive care unit. Optimal imaging was obtained in 91% of the patients, in whom a total of 82 measurements of cardiac output were performed. The respective mean (SD) areas of the aortic valve were 3.77 (0.71) cm2 in the transverse plane and 3.86 (0.89) cm2 in the longitudinal plane. A correlation of 0.87 was found between pulsed-wave Doppler cardiac output and the thermodilution technique in either transverse or longitudinal plane. Correlation coefficients of 0.82 and 0.84 were found between thermodilution cardiac output and transverse and longitudinal continuous-wave Doppler cardiac output, respectively. Although thermodilution cardiac output is a widely accepted clinical standard, transoesophageal Doppler echocardiography across the aortic valve offers adequate estimations of cardiac output. In particular, pulsed-wave Doppler cardiac output in both the transverse and longitudinal plane provides useful data.