Table 1. Use of critical care echocardiography in the setting of potential weaning failure of cardiac origin.
| Steps | Aims | Parameters |
|---|---|---|
| 1. Identify the high-risk population in a stabilized ventilated patient* | Screen patients to determine the high risk of weaning failure of cardiac origin | Any cardiomyopathy or relevant valvulopathy |
| LV systolic function: ejection fraction | ||
| Left atrial size | ||
| LV diastolic properties and filling pressure: E/A, E/E’, E deceleration time Systolic pulmonary artery pressure: maximal velocity of tricuspid regurgitation | ||
| 2. Characterize baseline central hemodynamics and LV diastolic properties | Determine baseline hemodynamic profile as a reference | LV ejection fraction |
| LV outflow tract velocity time integral | ||
| Regional LV systolic function assessment (wall thickening) | ||
| E/A and E/E’ (lateral and septal) | ||
| Semi-quantitative assessment of mitral regurgitation | ||
| Maximal tricuspid regurgitation velocity | ||
| 3. Assess SBT-induced hemodynamic changes | Depict a potential increase of LV filling pressure and other consequences of changes in cardiac loading conditions (use baseline values as reference) | Same as 2. |
| Significant increase of LV filling pressure requires adequate Doppler signal and variations of velocity greater than reproducibility of measurement which is less than 5% (47) | ||
| 4. Identify weaning pulmonary edema and its mechanism | Depict elevated (increased as compared to baseline) LV filling pressure | New-onset or worsened LV systolic dysfunction |
| Disclose the precise underlying mechanism | New-onset or extension of LV regional wall motion abnormalities | |
| Absence of increase or even decreased LV stroke volume | ||
| Increased E/A and E/E’ | ||
| Worsened mitral regurgitation (central if functional, eccentric if ischemic, systolic anterior motion)** | ||
| Worsened pulmonary hypertension | ||
| 5. Guide tailored therapy to best prepare patient for the next SBT | Document therapeutic efficacy (correction of the mechanism of initial weaning pulmonary edema) | Abnormality found at step 4. corrected or improved before scheduling the new SBT |
| 6. Monitor closely the next SBT after optimization of etiologic treatment | Rule out any significant hemodynamic change during SBT | Same as 2. and 3. |
*, see text for details; **, transesophageal echocardiography may be superior to the transthoracic approach for a precise diagnosis in a sedated patient under ventilation after SBT failure. LV, left ventricle; SBT, spontaneous breathing trial.