The goal of this observational study is to learn about the roles of critical closing pressure and tissue perfusion pressure in monitoring hemodynamic status, evaluating organ damage, and predicting mortality risk in patients with sepsis. The main question it aims to answer is:

• Whether increases in critical closing pressure or tissue perfusion pressure are associated with a reduced risk of poor prognosis?

Within the 24 hours following the diagnosis of sepsis, patients will be categorized into four groups based on their 24-hour mean critical closing pressure (Pcc) and tissue perfusion pressure (TPP) estimated from the hourly hemodynamic data within 24 hours. Outcomes will then be compared across these different groups.

The study has been approved by the Medical Ethics Committee of Peking Union Medical College Hospital (K24C1937 and K25C0792).

To validate the reliability of mean Pcc estimated in the primary analysis, we prospectively collected hemodynamic data over a 24-h period from adult ICU patients with invasive arterial monitoring. Two methods were employed to estimate the mean Pcc for reliability validation. Based on the results of preliminary experiment, the sample size calculation showed that at least 12 individuals were needed for reliability validation.

Inclusion Criteria:

• Age ≥18 years;
• Sepsis was diagnosed according to Sepsis 3.0 criteria;
• ICU stay exceeding 24 hours after enrollment;
• Undergoing continuous monitoring of vital signs.

Exclusion Criteria:

• Significant absence of blood pressure and heart rate data within 24 hours of enrollment;
• Pregnancy or breastfeeding;
• brain death.

Adult septic patients who were admitted to ICUs and received continuous monitoring of vital signs.

IPD will be shared upon proper requirement.

After publication of the study.

Upon proper requirement sent to the primary investigator.