Fluid therapy is important in patients with sepsis and septic shock. There are many invasive and non-invasive methods to assess fluid responsiveness in patients. The specificities and sensitivities of these methods are highly variable. The reason for our study was to determine end-tidal co2 and fluid responsiveness in septic shock patients. The aim of the study was to evaluate the fluid response using the End-tidal CO2 difference in septic shock patients receiving intubated mechanical ventilation support.

End-tidal CO2 is a parameter that can be easily measured with our non-invasively available monitors. If results are positive, fluid response of patients can be measured with a non-invasive, easy-to-apply method.

The significance of end-tidal CO2 will be confirmed by the passive leg raise test. Assessment of fluid responsiveness with the passive leg raise test is currently seen as the non-invasive reference test used.

It has proven its accuracy and reliability in many studies. In the passive leg raise test, end-tidal CO2 will be compared between the group with and without fluid responsiveness.

Scope of the study: Patients hospitalized in the general and reanimation intensive care units of our hospital and diagnosed with septic shock for any reason.

Method(s) to be applied: All patients diagnosed with septic shock will be included in the study.

The passive leg raise test, will be applied to the patients, and cardiac output and end-tidal CO2 changes will be recorded with transthoracic echocardiography before and after.

Fluid responsiveness is considered to be present in patients whose stroke volume variation output change measured by echocardiography increases by 10% or more after the passive leg raise test.

Patients will be divided into 2 groups according to fluid responsiveness. Group-1 group with fluid responsiveness in passive leg raise test, Group-2 group with no fluid response in passive leg raise test. End-tidal CO2 will be compared between groups.

Passive leg raise test: After the patients are in a semi-sitting position (at least 2 minutes), two healthcare professionals will take the supine position and then lift their legs 45 degrees, wait for 2 minutes and return to the initial position.

With this maneuver, it is anticipated that approximately 150-300 ml of autotransfusion will be administered to the patient.

Statistical analyzes will be made with the SPSS 21 program. Normally distributed data will be expressed as mean ± standard deviation, non-normally distributed data will be expressed as median. Categorical data will be expressed as a percentage. The difference between the mean and median values will be evaluated according to the distribution of the data by Student's t or Mann-Whitney U test. Categorical data will be evaluated with the chi-square test. A p value <0.05 will be considered significant.

Inclusion Criteria:

• over 18 years old
• in circulatory shock
• Hemodynamically stable for 10 minutes (whether or not he takes vasoactive drugs)
• Followed in mechanical ventilation with invasive arterial monitoring

Exclusion Criteria:

• pregnant
• Heart cannot be visualized by echocardiography
• Patients for whom passive leg raise test cannot be performed
• Bilateral lower extremity amputation
• Patients who are hemodynamically unstable

Patients hospitalized in the general and reanimation intensive care units of our hospital and diagnosed with septic shock for any reason