Septic shock is a condition of acute circulatory failure and is defined as a process that requires the use of vasopressors to ensure adequate tissue perfusion when hypotension develops. It is mainly characterized by abnormal peripheral vascular resistance; Therefore, improving vascular function and organ damage is crucial in the management of septic shock. Blood flow measurement with Doppler-based renal resistive index (RRI), which can be performed at the bedside, especially in renal abnormalities, is currently accepted as a tool to assess renal perfusion. With this simple, rapid and reproducible technique, the investigators determine RRI by evaluating systolic and diastolic blood velocity from Doppler flow waveforms in the intrarenal arcuate or interlobar arteries. Our aim is to investigate the relationship between renal resistive index (RRI) and global tissue hypoperfusion parameters and clinical outcomes in septic shock patients admitted to the intensive care unit and receiving invasive mechanical ventilator support.

It is planned for patients who are admitted due to septic shock and need invasive mechanical ventilator support, who have a central venous catheter inserted for central venous pressure measurement and advanced monitoring, and who have undergone invasive arterial monitoring for close hemodynamic monitoring. After initial hemodynamic stabilization is achieved, RRI will be calculated by renal ultrasonography within 24 hours. Simultaneously with renal ultrasonography, blood samples will be taken from arterial and central venous catheters, partial arterial oxygen pressure (PaO2), partial arterial carbon dioxide pressure (PaCO2), partial central venous oxygen pressure (PcvO2) and partial central venous carbon dioxide pressure (PcvCO2), arterial Oxygen saturation (SaO2), central venous oxygen saturation (ScvO2), hemoglobin concentration and arterial lactate levels will be recorded. An attempt will be made to gain an idea about the course of the disease by comparing RRI with these global tissue hypoperfusion parameters.

Inclusion Criteria:

• Followed up due to sepsis
• In need of intensive care follow-up
• In need of invasive mechanical ventilation
• Sofa score >2

Exclusion Criteria:

• Hypothermic patients (<35C)
• with chronic renal failure
• Pregnant women
• Those with renal artery stenosis
• Structural kidney damage
• Patient with previous renal surgery
• Intra-abdominal postoperative surgery patients
• Patients with atrial fibrillation

It is planned for patients who are admitted due to septic shock and need invasive mechanical ventilator support, who have a central venous catheter inserted for central venous pressure measurement and advanced monitoring, and who have undergone invasive arterial monitoring for close hemodynamic monitoring.