Critical Care: Imaging in Critical Illness |

Carotid Flow Measurement Variability in Shock Using Point of Care Ultrasound FREE TO VIEW

Venkata Ravi Kumar Angirekula; Ziad Shaman
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Case Western Reserve University/Metrohealth Medical Center, Cleveland, OH

Copyright 2016, American College of Chest Physicians. All Rights Reserved.

Chest. 2016;150(4_S):296A. doi:10.1016/j.chest.2016.08.309
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SESSION TITLE: Imaging in Critical Illness

SESSION TYPE: Original Investigation Slide

PRESENTED ON: Tuesday, October 25, 2016 at 11:00 AM - 12:15 PM

PURPOSE: Carotid blood flow ultrasonography has been increasingly used to assess the intravascular volume status in critically ill patients. Measurements of carotid blood flow with passive leg raise or after a fluid challenge is gaining importance in caring for patients in emergency rooms and intensive care units. A study of sonographers by Tanuguchi et al reported reasonable agreement in measuring carotid blood flow in healthy volunteers, but there are no studies looking at agreement in patients with shock. Also, there are no studies describing variability in physicians performing these carotid measurements. Considering the importance of carotid ultrasound in hemodynamic assessment, this study is conducted to examine the intra-observer and inter-observer variability in physicians measuring carotid blood flow in patients with shock.

METHODS: Aim: To describe the intra-observer variability in physicians measuring carotid blood flow by ultrasound in patients with shock. Consecutive adult patients with shock who were admitted to Medical Intensive Care Unit were included in the study as part of standard assessment of volume responsiveness by measuring carotid blood flow before and after passive leg raising test. Patients were excluded from the study if they were unable to lay flat or if their legs could not be raised. Carotid doppler blood flow measurements were performed by two critical care physicians trained in the use of point of care ultrasound. Carotid artery flow measurements were performed twice by each physician with patients laying on the bed with head end at 45 degree angle. Scanning sequence was randomized between the physicians. Physicians were blinded to each other and also blinded to the measurements made in each of their examinations.

RESULTS: Carotid blood flow measurements were performed twice by each physician on 42 different occasions that included 24 patients. Patient ages average was 64.2 (+/-21.1) years, their BMI was 31.3 (+/- 10.4) kg per meter square, most patients were in regular heart rhythm (95%), and spontaneously breathing (72%). When ventilated, the average tidal volume was 7 (+/- 0.8) cc per kg ideal body weight. Twenty percent or less variability in carotid blood flow was seen in 45% of the measurements. While 50% or less variability was seen in 80% of the measurements. When evaluating each of the individual physicians separately, similar numbers were seen (42.8% and 85.7% for physician 1, and 47.6% and 73.8% for physician 2, respectively). There was no significant difference in the mean of the measurements performed by the 2 physicians when compared using t-test (p 0.06).

CONCLUSIONS: Intra-observer variability in measuring carotid blood flow in patients with shock is high. There was no significant difference in the performance of point of care ultrasound when used by 2 physicians.

CLINICAL IMPLICATIONS: The variability in carotid blood flow measurement exceeds what has been recommended as a cutoff (20%) to determine volume responsiveness in patients with septic shock using passive leg raising. A cutoff of more than 50% may be more appropriate to distinguish volume responsive from nonresponsive patients with shock.

DISCLOSURE: The following authors have nothing to disclose: Venkata Ravi Kumar Angirekula, Ziad Shaman

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