The critically ill patient is one of the most complex cases with regard to the optimization of the anesthesia, as well as postoperative management. One of the most important steps in the complex management of such patients is the modulation of anesthesia for every patient needs. We start with the assumptions that the optimization of anesthesia should depend on each patient, being conducted in an individual manner. We also believe that by individualizing the anesthesia by monitoring the entropy it is possible to obtain an appropriate management regarding hemodynamic complications during anesthesia including tachycardia, bradycardia, hypotension and hypertension.