 1. Control group. The patient will receive treatment according to septic shock guideline 2013, which start with intravenous fluid replacement until achieve target central venous pressure CVP or pulmonary capillary wedge pressure PCWP or other fluid responsive test goal. If the patients mean arterial blood pressure still lower than 65 mmHg, then norepinephrine or dopamine will initiate to rise blood pressure. The patient will receive 5 dextrose water as the placebo of norepinephrine. 