GCIV as an Adjuvant Therapy for Community-Acquired Severe Sepsis or Septic Shock

Inclusion Criteria: * Patients with severe sepsis or septic shock, if all of the following criteria is satisfied. 1. Age ≥ 18 years 2. Proved or suspected infection in at least one site * pneumonia * urinary tract infection * intra-abdominal infection * primary bloodstream infection * skin and soft tissue infection 3. Three or more of the following * a core temperature ≥ 38° C or ≤ 36° C * a heart rate ≥ 90 beats/min * a respiratory rate ≥ 20 breaths/min or PaCO2 ≤ 32 mmHg or use of mechanical ventilation for an acute process * a white blood cell count ≥ 12000/mm3 or ≤ 4000/ mm3 or immature neutrophils \> 10% 4. Acute organ failure in one or more of the following * kidney * respiratory system * blood system * metabolic system * circulatory system 5. APACHE score ≥ 20 and ≤ 29 6. Patient can treatment with GCIV in ICU within at least 48 hours 7. Informed consent Exclusion Criteria: 1. Pregnant or breast-feeding women 2. a weight \> 100kg 3. discharged from the hospital at least 14 days prior to new admission 4. Transferred from another hospital staying more than 48 hours 5. allergy or shock of IVIG 6. Treated with IVIG within the 12 weeks immediately preceding enrolment in this study 7. IgA deficiency 8. Hypernatremia or hyperhydration 9. Proved or suspected HIV or AIDS patients(CD4+ \<200mL) 10. Current participation in any study within the last 4 weeks 11. Do not resuscitate (DNR) status 12. Patient's death is considered imminent due to coexisting disease 13. physicians decision to exclude patients from this protocol 14. Immunocompromised patients