The purpose of this study is to explore and assess possible outcome benefits of lactate clearance>30% vs ScvO2 ≥70% in 6 hours as the protocol goal that evaluated adequacy of during early resuscitation of septic shock through a single-center randomized controlled study. The investigators anticipate to collect 300-400 qualified patients with septic shock who were selected from critically ill patients admitted to the Department of Critical Care Medicine. The participants can be randomized divided into lactate clearance group and SCVO2 group. The investigators compared the treatment and the relevant parameters changed after different target. 28-day mortality, ICU and hospital lengths of stay, ventilator-free days, and new emerged organ failure were collected and compared. 28-day survival curves were drew between these two group. And the adverse events of the treatment have also been compared. Through this study, the investigators want to answer that whether lactate clearance-oriented therapy can reduce the mortality in patients with septic shock, compared with ScvO2-oriented protocolised therapy.

Inclusion Criteria:

• Patients with septic shock were assessed for inclusion, which required that patients be older than 18 years with confirmed or presumed infection, met two or more criteria for systemic inflammatory response syndrome [16], and evidence of refractory hypotension or a serum lactate level above 4 mmol per liter.
• Refractory hypotension was defined as a systolic blood pressure lower than 90 mm Hg, or a mean arterial pressure of less than 65 mm Hg , after an intravenous fluid challenge of 20 ml or more per kilogram of body weight.
• Patients had to be enrolled in the study within 2 hours after the earliest detection of septic shock and within 12 hours after arrival ICU.

Exclusion Criteria:

• The patients were excluded if they meet any one of follows: an age of less than 18 years, pregnancy, an acute cerebral vascular event (Glasgow coma score < 5), acute myocardial infarction or acute coronary syndrome, massive pulmonary embolism, status asthmaticus, a primary diagnosed cardiac dysrhythmias, contraindication to central venous catheterization, active gastrointestinal hemorrhage, massive intra abdominal infective focus without drainage, severe bronchopleural fistula, seizure, during chemotherapy or immunosuppressive therapy, or end stage of the diseases.