Assessment of loading conditions with cardiac ultrasound. A comprehensive review

Optimization of the preloading conditions and concomitant determination of endpoints of fluid administration are the most frequent therapeutic actions in critically ill patients. Besides a clinical appraisal, reproducible data should be acquired at the bedside to estimate the adequacy of fluid resuscitation. The dynamic assessment and determination of fluid responsiveness plays a major role in this respect. Right-sided cardiac variables, such as inferior and superior caval vein diameter variation during mechanical ventilation, are easily obtained with cardiac ultrasound. Moreover, left sided variables, including aortic flow variation, with intermittent swings of intrathoracic pressure during mechanical ventilation, may be achieved non-invasively with Doppler-echocardiography. Both in terms of resuscitation, as well as correct interpretation of various two-dimensional and Doppler variables, it is essential to acquire a clear understanding of the filling status of a patient. Doppler-echocardiography plays herein a pivotal role.