In this prospective, single-center,randomized,controlled,single-blind clinical trial,Patients will be randomly assigned to receive granisetron or placebo for 4 days or until leaving the ICU(death or transfer from ICU to general ward or discharge). The primary outcome is all-cause death rate at 28 days.

Investigational drug：Granisetron hydrochloride for injection

Study title：Adjunctive Granisetron Therapy in Patients with Sepsis or Septic Shock:A Single-center,Randomized,Controlled,Single-blind Clinical trial.

Principal Investigator：Professor Ping Chang ,Professor Zhanguo Liu, professor Peng Chen,Department of Critical Care Unit, Zhujiang Hospital, Southern Medical University

Study subjects：Adult septic/septic shock patients with procalcitonin(PCT≥2ng/ml when entering the ICU.

Study phase： Investigator Initiated Trial(IIT)

Study objectives：The objective of the study is to determine whether granisetron, compared to placebo, improve the prognosis of sepsis or septic shock,including the reduction in mortality, the protection of organ function and reduction of inflammatory response,and to determine the safety of granisetron in patients with sepsis.

Study design：A Single-center,Randomized,Controlled,Single-blind Clinical trial.

Medication method： Granisetron treatment group： Follow the guidelines for sepsis in 2016 and recommend routine treatment + 3mg granisetron in 22 ml normal saline every 8 h for 4 days or until leaving the ICU(death or transfer from ICU to general ward or discharge), whichever come first.

Placebo control group：Follow the guidelines for sepsis in 2016 and recommend routine treatment + 25ml normal saline every 8 h for 4 days or until leaving the ICU(death or transfer from ICU to general ward or discharge), whichever come first.

Course：4days

Sample size：154.

Sites：1

Primary endpoint：all-cause death at 28 days

Secondary endpoints:

1. The state of liver function: the serum level of transaminase(AST、ALT)、total bilirubin、direct bilirubin at 1,2,3,4,5 days after randomization
2. The state of lung function:oxygenation index(PaO2/FiO2) at 1,2,3,4,5 days after randomization (the patients treated with extracorporeal membrane oxygenation will not collect this indicator).
3. The state of kidney function:serum level of Creatinine (Cr)、blood urea nitrogen(BUN)、Cystatin(Cys) at 1,2,3,4,5 days after randomization
4. The state of inflammatory response:the serum level of interleukin-6(IL-6) 、C-reactive protein 、Superoxide dismutase(SOD) and erythrocyte sedimentation rate(ESR) at 1,3,5 days after randomization.
5. The state of circulation system: the serum level of lactic acid at 1,2,3,4,5 days after randomization
6. The state of immune function:the serum level of white blood cell(WBC)、lymphocyte at 1, 3, 5 days after randomization,the serum level of cluster of differentiation 4 Tcell(CD4+ Tcell) and cluster of differentiation 8 Tcell(CD8+ Tcell) at 1,5days after randomization.
7. The level of plasma 5-hydroxytryptamine(5-HT) at 1,5 days after randomization.
8. Organ dysfunction assessed by Sequential Organ Failure Assessment (SOFA) score at 1, 3, 5 after randomization
9. Incidence and duration of supportive care for organ dysfunction including vasoactive agents, mechanical ventilation, continuous renal replacement therapy(CRRT)、daily condition of fuid balance
10. The length of stay in ICU

Safety endpoints：

1. adverse events
2. Serious adverse events

Inclusion Criteria(Only patients who fully meet the following criteria are eligible to participate in the trial):

• Meets the diagnostic criteria for sepsis-3 developed by the American Society of Critical Care Medicine (SCCM)/European Critical Care Medicine Association (ESICM)
• Age ≥18 years old and age ≤80years old.
• Procalcitonin ≥2ng/ml

Exclusion Criteria:

• Age<18 years, or age>80 years.
• Pregnancy or lactating
• A solid-organ or bone marrow transplant patients.
• Patients with myocardial infarction within the past 3 months.
• Advanced pulmonary fibrosis .
• Patients with cardiopulmonary resuscitation before enrollment.
• HIV-positive patients.
• granulocyte-deficient patients.
• blood/lymphatic system tumors are not remission.
• patients with limited care (lack of commitment to full，aggressive life support).
• patients with long-term use of immunosuppressive drugs or with immunodeficiency.
• patients with advanced tumors.
• patients combined with non-infectious factors leading to the death(uncontrollable major bleeding, brain hernia, etc.).
• surgically unresolved infection sources(such as some intraperitoneal infection etc.)
• patients allergic to granisetron.
• patients with intestinal obstruction.

since some data may involve patients privacy ，we have no plans to share data so far，and some data may be shared later depending on the patient's wishes.