This study innovatively utilizes multi-modal hemodynamic monitoring (Norepinephrine equivalence, NEE+Pulse indicator Continuous Cariac output, PiCCO) to investigate the optimal timing of initiation of oXiris in abdominal infection-associated septic shock patients and to investigate prognosis on sepsis phenotypes undergoing oXiris therapy.

Sepsis is a life-threatening organ dysfunction syndrome caused by dysregulated host responses to infection, which is one of the leading causes of death for critically ill patients and also a challenge for clinicians.

Abdominal infection is a common cause of septic shock, and is often transferred to intensive care unit (ICU) from emergency surgery, including appendectomy, cholecystectomy, intestinal repair or resection, incision and drainage of abscesses, and local debridement.

The oXiris (Baxter) hemofiltration membrane is the only one on the market with the ability to adsorb both cytokines and endotoxin. This, together with the renal replacement function and its antithrombogenic properties, makes it unique in that it brings together four important functions in a single device. Endotoxin adsorption occurs thanks to a significant number of positively charged free amino groups in Polyethylene imine (PEI), which bind to the negatively charged endotoxin. This capacity is much more important, as oXiris has significantly more PEI compared to previous membranes. Therefore, from the perspective of structural principle, oXiris is currently an ideal adsorptive blood purification filter, which can not only perform conventional renal replacement therapy, but also perform adsorptive therapy to provide extra-renal support for sepsis. Therefore, in terms of the structural properties of the membrane, oXiris is currently an ideal adsorptive blood purification filter for both conventional renal replacement therapy for renal dysfunction treatment and extra-renal support for sepsis with endotoxin adsorption therapy.

The investigaters hypothesis the adsorptive filter oXiris using for continuous renal replacement therapy (CRRT) can improve hemodynamic instability in abdominal septic shock patients, which rely on multimodal hemodynamics monitoring by PiCCO and ultrasound for early goal directed therapy.

Inclusion Criteria:

1. Age ≥18 years;
2. Weight ≥30 kg;
3. Intra-abdominal infection (blood or abdominal drainage fluid culture positive for Gram-negative bacteria or suspected to be caused by a Gram-negative agent);
4. Diagnostic septic shock (Sepsis 3.0): Sepsis was defined as "life-threatening organ dysfunction caused by a dysregulated host response to infection" with organ dysfunction defined as an increase in qSOFA ⩾2 points. Septic shock was defined as sepsis requiring vasoactive therapy to maintain mean arterial pressure (MAP) ⩾ 65 mmHg and lactate elevation to >2 mmol/L despite adequate volume resuscitation;
5. The dose of norepinephrine⩾0.4ug/kg/min;
6. PCT⩾50ug/L, and/or IL-6⩾1000pg/ml;
7. AKI stage II/III (Kidney Disease Improving Global Outcomes, KDIGO grade);
8. Duration of septic shock ≤48 hours.

Exclusion Criteria:

1. Patients with highly contagious infectious diseases, such as tuberculosis;
2. Pregnant and lying-in woman or lactation period;
3. Infection of other sites (no abdominal infection like pneumonia, central nervous system infection and so on);
4. CRRT cannot be performed for various reasons;
5. Death is expected within 48 hours of admission to the ICU;
6. Previous renal replacement therapy;
7. Patients that underwent cardio-pulmonary resuscitation (CPR);
8. Patients who will not sign the informed consent form.