LAUSR

Introduction/Hypothesis: Point of care ultrasound (POCUS) is increasingly being used to determine fluid responsiveness in critically ill patients. Due to increased familiarity with Inferior Vena Cava (IVC) diameter measurement, it is still being used as a marker for volume responsiveness, despite several known limitations. Here, we propose carotid doppler flow variation with passive leg raise (PLR) is easier to learn, and possibly a superior test to determine fluid responsiveness. Methods: Internal Medicine residents with no prior experience in POCUS were trained with a hands-on session. Twelve ICU patients who were in sinus rhythm and not receiving fluid resuscitation were selected, and informed consent was obtained. The resident and Critical Care Physician (CCP) measured respirophasic IVC variability and change in common carotid flow with PLR. An unbiased recorder noted the results. A positive test was defined as IVC collapsibility index of >40% in spontaneously breathing patients, IVC distensibility >18% in patients on controlled mechanical ventilation, and an increase in carotid blood flow by ≥ 20% with passive leg raise. Concordance of data between the newly trained resident and CCP was determined using Cohen’s kappa coefficient (κ). Results: Carotid measurements were obtained in all 12 patients by resident and CCP. There was moderate concordance between the resident and CCP as evidenced by κ of 0.59, P=0.009. Out of 12 patients, IVC measurements were obtained in 11 by the CCP, and in 9 by the residents. In the patients whose IVC measurements were obtained, there was moderate concordance between the resident and CCP; κ 0.67, P=0.01. Conclusions: Here, we demonstrate that training residents in carotid flow variability with PLR is easier to learn. The IVC being a deeper structure makes it harder to locate, and despite similar training sessions, only 9 out of 12 residents were able to perform IVC measurements, while all were able to perform carotid doppler. Carotid doppler accounts for preload, contractility and afterload, whereas respirophasic IVC diameter (IVCd) changes only accounts for preload, making it an inherently superior test to determine fluid responsiveness. We propose allocating time and resources to train residents in measuring carotid artery flow instead of IVCd to ascertain fluid responsiveness.