Inclusion Criteria:  1. Must be suspected by the treating physician to have sepsis as the primary cause of their acute illness as exhibited by 2 or more of the following Systemic Inflammatory Response Syndrome (SIRS) criteria:  Temperature of > 38 C or < 36 C Heart rate of > 90/min Respiratory rate of > 20/min or PaCO2 < 32 mm Hg White blood cell count > 12000/mm3 or < 4000/mm3 or >10% immature bands. 2. Known or suspected infection at the time of screening 3. Admission to the ICU for <24 hours  Since approximately 12% of patients ultimately diagnosed with sepsis do not meet SIRS criteria, SIRS negative patients will be eligible for the study if the treating physician makes a clinical diagnosis of severe sepsis or septic shock.  Exclusion Criteria:  Patients with conditions that may interfere with portal Doppler assessments such as cirrhosis or portal thrombosis Patients with severe chronic kidney disease (estimated glomerular filtration rate<15 mL/min per 1.73 m2 calculated using the Modified Diet in Renal Disease formula). Age < 18 years Active atrial fibrillation or atrial flutter Hemodynamic instability due to active hemorrhage Acute cerebral vascular event Acute coronary syndrome (excluding elevated troponin thought to be from demand ischemia) Acute pulmonary edema Status asthmaticus Drug overdose Injury from burn or trauma Status epilepticus Indication for immediate surgery Received CPR within 24 hours of enrollment Pregnancy Incarceration.