Extension of the Rapid Ultrasound for Shock and Hypotension to Evaluate Volume Responsiveness

Background & Motivation: Non-traumatic shock accounts for millions of emergency department visits every year and is a significant burden on the health care system making rapid identification and treatment essential. For decades the Rapid Ultrasound in Shock and Hypotension (RUSH) exam has been employed to help determine the etiology of non-traumatic shock in the ED setting. The RUSH exam does not answer other critical questions such as the need for additional fluid resuscitation. The current study hypothesizes that by include a step-wise cardiopulmonary algorithm the RUSH exam can be extended (E-RUSH) to accurately determine the need for additional fluid therapy.

Study Design: Prospective Observational Study in two urban Emergency Departments with a combined annual census of >111,000.

Population: ED patients exhibiting signs of shock definied by a systolic blood pressure < 100 mmhg, MAP < 65, persistent tachycardia, mottled skin, or lactate >2mmol either at presentation or during ED stay will be included. Exclusion criteria will be inability to consent, external factors preventing ultrasound examination, age less than 18, pregnancy, incarceration, arrhythmia, cardiac arrest, or treating physician gestalt that the patient is not in shock.

Protocol: The E-RUSH protocol will include ultrasound exams of the IVC, heart and lungs as described in the RUSH protocol but will also evaluate cardiac output, IVC collapsibility, and presense of B-lines on lung ultrasound. At the time of ultrasound measuresments a bioreactance device will be applied. Bioreactance measurements and ultrasound measurement of cardiac output will be recorded pre and post a passive straight leg raise test. All charts will be reviewed by two experts who are blinded to ultrasound and bioractance measurements. When possible the protocol will be repeated 1-2 hours later or after initial interventions in order to provide trend data.

Data Analysis: Volume responsivness as assessed by the E-RUSH will be defined a priori using a step-wise flow diagram that combines IVC, lung and cardiac ejection fraction and output measurements (see research plan for details). Determination of volume responsiveness by the bioreactance device will be defined by manufacturer protocal. Determination of volume responsiveness by expert review will be by a standard abstraction form with agreement of both expert reviewers. Descriptive statistics will be performed to determine the test characteristics of the ultrasound protocol to predict volume responsiveness. Given the lack of a universally agreed upon gold standard for volume responsiveness, we will determine test characteristics for E-RUSH using the bioreactance device as a reference standard and using expert review as a second reference standard separately.