There is debate regarding the use of non invasive (ultrasound assessed) parameters of fluid volume status in patients with sepsis.

To establish the role of inferior vena cava ultrasound in guiding fluid resuscitation we first need to define the inferior vena cava collapsibility index in this population of patients.

The research question is: In adult patients with sepsis, severe sepsis and septic shock what is the mean baseline inferior vena cava collapsibility index (IVCCI) prior to fluid resuscitation.

The study is an interventional cohort study using a convenience sample of adult patients in a university teaching hospital Emergency Department.

Eligible participants who consent to partake in the trial will have an ultrasound assessment of their inferior vena cava performed and the IVCCI will be calculated at enrolment.

Care will be provided in line with the published guidelines on sepsis management from the Surviving Sepsis Campaign and the College of Emergency Medicine.

A sample size calculation has been performed which indicates that 112 patient with severe sepsis or septic shock will need to be enrolled.

Inclusion Criteria:

• Adult patients
• signs and symptoms of infection with 2 or more SIRS criteria (pulse rate >90/min, Temp > 38 Celsius < 36 Celsius, Respiratory rate > 20 breaths per minute, or white cell count >12 or <4 x 10^9/L)

Exclusion Criteria:

• in relation to this episode of care: Prior cardio pulmonary resuscitation, acute myocardial infarction, trauma, pregnancy or patient requiring immediate surgery.
• Patients who have received more than 20ml/Kg of IV fluid in the pre hospital environment
• Patients with known tricuspid regurgitation, congestive heart failure or pulmonary hypertension
• Patients receiving palliative terminal supportive care