The purpose of this study is to investigate whether cardiac output (CO) and global end diastolic volume (GEDV) determined from the same thermodilution curve by EV1000 are mathematically coupled during the infusion of fluid or inotropic agents in critically ill patients.

Some fundamental questions remain unanswered about the mathematical analysis of the thermodilution curve and the physiological significance of the Global End Diastolic Volume ( GEDV ) .

The mathematical derivation of the Global End Diastolic Volume (GEDV) is intimately linked with the Cardiac Output (CO), because EV1000, to calculate the GEDV, uses a formula in which the CO is the term "flow " for both the calculations of Volume Thermal Intra Thoracic (ITTV) and Lung Thermal volume (PTV) .

The clinical validation of GEDV as an index of preload has been substantially based on measuring changes in GEDV and CO in response to the Fluid Challenge only in patients "volume responsive".

In this scenario, GEDV and CO may show a close correlation only on the basis of their mathematical derivation.

Inclusion Criteria:

• patient admitted in the Intensive Care Department
• patient monitored by EV1000 trans pulmonary device
• Systolic blood pressure (SBP) less than 90 mm Hg or SBP Drop ≥ 40 mm Hg of normal
• decision by 1 expert intensivist physician to initiate fluid resuscitation hospital protocol or therapeutic infusion of vasopressor agent

Exclusion Criteria:

• pregnancy
• age less than 18

Critically ill patients