The study aim is to examine point-of-care ultrasound findings, reliability, and ease of performance in association with fluid responsiveness for patients with severe sepsis and septic shock. The investigators propose a prospective observational research study of patients presenting to one of three Yale New Haven Hospital emergency departments, York Street Campus, St. Raphael's Campus, and Shoreline Medical Center who meet criteria for sepsis, severe sepsis or septic shock during their emergency department visit.

After each 1 Liter fluid challenge of IV fluid each outcome measure will be repeated to determine if there is a change in ultrasound measures as patients undergo volume resuscitation.

Inclusion Criteria:

• All patients age greater than 18 years who meet criteria of sepsis. Septic shock will be defined as those patients with severe sepsis and persistent hypotension (<90mmHg systolic blood pressure) despite a fluid challenge of at least 20cc/kg
• Patients will only be considered eligible for enrollment if the treating physician plans to give at least 1-liter of crystalloid after initial US is performed
• A number (approximately 50 patients) with no symptoms of sepsis will be enrolled to assess measurements in healthy patients. These patients will only have one ultrasound performed for each of the desired study measures.

Exclusion Criteria:

• Patients unable to provide consent such as non-English speaking patients or patient/health care proxy unable to give consent
• History of significant trauma
• Incarcerated patients
• Failure to complete fluid challenge
• Pericardial disease or heart transplant. Patients with left bundle branch block, pulmonary hypertension, known systolic dysfunction (Ejection Fraction <40%), receiving vasopressors, known moderate or severe valvular dysfunction, and irregular heart rhythms will be enrolled but analyzed separately

Patients presenting to one of three Yale New Haven Hospital emergency departments, York Street Campus, St. Raphael's Campus, and Shoreline Medical Center who meet criteria for severe sepsis or septic shock during their emergency department visit. A number of healthy patients will also be enrolled to act as controls for this study.