Comparison of Non-Invasive Methods of Assessing Fluid Responsiveness in ED and ICU Patients

This is a diagnostic accuracy study comparing selected ultrasound techniques to a well validated standard for predicting fluid responsiveness in septic patients (NICOM). The primary outcomes will be reported in sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratios, and receiver operating characteristic curves.

The timeframe for measurement is within 72 hours of the subjects' admission. Determination of the outcome (i.e., whether a subject is fluid responsive) is based upon the data generated by the NICOM device. The NICOM generates data within 5 minutes of assessment. The ultrasound modalities to be studied will generate data within 5 minutes of assessment as well. The US data will be compared to the NICOM data to generate the statistics listed in this protocol. There is no further planned follow-up for the subjects.

• The investigators will compare the ability of dynamic changes in inferior vena caval diameter (IVC-CI), dynamic changes in peripheral arterial waveform derived variables (PA Doppler), and dynamic changes in left ventricular outflow tract waveform derived variables (LVOT Doppler) to detect fluid responsiveness (FRes) relative to FRes as assessed by bioreactance cardiac output monitoring before and after passive leg raise (PLR).

Hypothesis: PA Doppler and LVOT Doppler will have superior sensitivity and specificity to predict FRes in comparison to IVC-CI.

• The investigators will evaluate data acquisition duration and data acquisition failure rate of IVC-CI, PA Doppler, and LVOT Doppler. Hypothesis: PA Doppler will have shorter data acquisition durations in comparison to LVOT velocity variation and IVC-CI.

Hypothesis: PA Doppler will have lower data acquisition failure rates in comparison to LVOT velocity variation and IVC-CI.

• The investigators will compare the ability of IVC-CI, PA Doppler, and LVOT Doppler to predict FRes in comparison to FRes as predicted by clinical judgment.

Hypothesis: PA Doppler and LVOT Doppler will have superior sensitivity and specificity to predict FRes in comparison to clinical judgment.

• The investigators will evaluate the ability of dynamic changes in PA corrected flow times (cFT) to detect FRes relative to FRes as assessed by bioreactance cardiac output monitoring before and after PLR. Hypothesis: cFT will have greatest sensitivity and specificity to predict FRes at a Δflow time threshold of ≥15% after PLR.

Hypothesis: At a Δflow time threshold of ≥15%, cFT will have superior sensitivity and specificity to detect FRes in comparison to IVC-CI.

Inclusion criteria

• Subjects presenting to the ED will be screened in accordance with the Olive View Medical Center Sepsis Waiver, and subjects meeting two of the following four criteria will be eligible for inclusion in the study: Temperature >38/100.4 or <36/96.8, heart rate >90, respiratory rate >20 or PaCO2<32, and WBC >12K or <4K or > 10% bands (neutrophils). The clinical team will be contacted regarding patients identified based on this initial screening, and if the patient is determined to have a suspected infection and a fluid bolus is planned, the patient will be enrolled in the study if they meet the following criteria:
• Adult between the age of 18 to 90 years old;
• Not pregnant;
• Not using non-invasive positive pressure ventilation (CPAP or BiPAP);
• No history of heart, lung, and/or liver transplant;
• Not determined by the clinical team to be acutely unstable requiring immediate intervention at the time of data collection, and;
• No contraindications to a passive leg raise test (known or suspected cranio-cerebral or C-spine injury, venous thrombosis, orthopedic injury requiring immobilization or traction, or other contraindications as per clinical team).

Exclusion criteria

• Pregnant;
• Using non-invasive positive pressure ventilation (CPAP or BiPAP);
• Presence of or suspected elevated intracranial pressure;
• Presence of central venous catheters or other medical devices that prevent the use of bedside ultrasound;
• History of heart, lung, and/or liver transplant;
• History of critical aortic stenosis or severe aortic insufficiency;
• Determined by the clinical team to be acutely unstable and requiring immediate intervention at the time of study enrollment or data collection or;
• Has a contraindication to passive leg raise maneuver, e.g. known cervical spinal injury, deep venous thrombosis, orthopedic injury requiring immobilization or traction.