Critical patients are a real challenge for intensive care doctors due to the complex pathophysiology associated to these cases. Thus, for the assessment and monitoring of the critical patient a number of diagnostic methods are required. After all, we can say that the clinical success of a critical patient is represented by an accurate and precise evaluation and monitoring. In this book we want to present the latest methods of assessment and monitoring of a critical patient. We believe that this book can be extremely helpful for all intensive care physicians. Also, this book can help students and researchers who wish to update their knowledge on new methods of monitoring and evaluation of critical patients.