Novel applications of bedside monitoring to plumb patient hemodynamic state and response to therapy.

Abstract

Hemodynamic monitoring is essential during the treatment of the critically ill in order to address the hemodynamic alterations and assess the response to treatment. Traditionally classified causes of shock and underlying pathophysiological mechanisms are often neglected by resuscitative strategies included in the guidelines. Most of hemodynamic management focuses on the ability to early recognize patients susceptible to increase cardiac output (CO) and mean arterial pressure (MAP) after a defined fluid challenge by eliciting Starling's law of the heart, and less is known of the ones presenting in shock and not volume responsive. All this influences the application of hemodynamic monitoring tools and their interpretation. Functional hemodynamic monitoring strategies, aiming to overcome limitations of traditional static pressures measurements, have been developed and recently acknowledged by guidelines for the treatment of septic shock. Nevertheless, those techniques share the same limitations of previous ones, being poorly reliable in various common situations such as in spontaneous breathing patients, right ventricular dysfunction of several causes or if arrhythmia occurs. Echocardiography has now become commonplace in the evaluation of the hemodynamic profile in the critically ill and mastering this technique is important in order to interpret pathophysiological patterns behind hemodynamic alteration while at the same time, screening for unexpected findings. More recently, pathophysiological and echocardiographic-based approaches have been introduced to investigate ventriculo-arterial coupling, the relationship between both left and right heart and the relative circulatory bed. Such techniques allowed establishing that in many critically ill scenarios, coupling between the heart and the circulation is inefficient and probably that is the reason why in this case hemodynamic restoration cannot be achieved by standard approaches. Combining echocardiography to better understand and treat in real-time pathophysiological determinants of altered hemodynamic states with functional approaches seems to be the key to plumb hemodynamic states although it remains to be demonstrated if this tailored approach will improve patient outcome.