Investigation of the Role of Brain Natriuretic Peptide and Lactate in Early Goal-directed Therapy for Patients With Severe Sepsis and Septic Shock

B-type natriuretic peptide (BNP) is a cardiac neurohormone which rapidly released by the ventricle in response to myocardial stretch. BNP has been used as a biomarker of sepsis related cardiac dysfunction and volume overload in critical ill patients. It is also a marker associated with prognosis in patients with severe sepsis and septic shock. However, the clinical utility of BNP level in management of early severe sepsis and septic shock over the first 48 hours is not clear. Besides, Lactate represents as a maker of tissue hypoperfusion, which has been used as a guide therapy for sepsis patients and high serum lactate level is independently associated with mortality in severe sepsis. Today, in management of early severe sepsis and septic shock, current guideline emphasize the early goal-directed therapy (EGDT) with achieving the central venous pressure (CVP) level 8-12 mmHg by fluid support first, then targeting the next goal to maintain mean airway pressure (MAP) at least 65 mmHg by vasopressor agent (ie, Norepinephrine) and finally keeping central venous oxyhemoglobin saturation (ScvO2) > 70% via optimal Hct > 30% and dobutamine usage within first 6 hours of emergency department admission. However, the role of BNP and lactate in patients with severe sepsis and septic shock with or without myocardial dysfunction under EGDT management are not clear.

The investigators will conduct a prospective observational study to investigate the change of BNP and Lactate within 48 hours in early severe sepsis and septic shock under EGDT management, their association of cardiac dysfunction and their role in predicting various clinical outcome. The investigators also want to see if BNP and lactate could be useful tools to guide the adjustment of optimal fluid supply and the timing of inotropic agent intervention.