TNF and systemic inflammatory response syndrome: Besides, we also investigated the protective effect of therapeutic ketamine (2, 10, and 20 mg/kg 20 min after TNF-α injection), as well as prophylactic (1, 5, and 10 mg/kg 20 min before TNF-α injection) combined with therapeutic ketamine (1, 5, and 10 mg/kg 20 min after TNF-α injection) on survival rate in mice with SIRS.