The time cost of physiologically ineffective intravenous fluids in the emergency department: an observational pilot study employing wearable Doppler ultrasound

Abstract

Background: Little data exist on the time spent by emergency department (ED) personnel providing intravenous (IV) fluid to 'responsive' versus 'unresponsive' patients.

Methods: A prospective, convenience sample of adult ED patients was studied; patients were enrolled if preload expansion was indicated for any reason. Using a novel, wireless, wearable ultrasound, carotid artery Doppler was obtained before and throughout a preload challenge (PC) prior to each bag of ordered IV fluid. The treating clinician was blinded to the results of the ultrasound. IV fluid was deemed 'effective' or 'ineffective' based on the greatest change in carotid artery corrected flow time (ccFT_∆) during the PC. The duration, in minutes, of each bag of IV fluid administered was recorded.

Results: 53 patients were recruited and 2 excluded for Doppler artifact. There were 86 total PCs included in the investigation comprising 81.7 L of administered IV fluid. 19,667 carotid Doppler cardiac cycles were analyzed. Using ccFT_∆ ≥ + 7 ms to discriminate 'physiologically effective' from 'ineffective' IV fluid, we observed that 54 PCs (63%) were 'effective', comprising 51.7 L of IV fluid, whereas, 32 (37%) were 'ineffective' comprising 30 L of IV fluid. 29.75 total hours across all 51 patients were spent in the ED providing IV fluids categorized as 'ineffective.'

Conclusions: We report the largest-known carotid artery Doppler analysis (i.e., roughly 20,000 cardiac cycles) in ED patients requiring IV fluid expansion. A clinically significant amount of time was spent providing physiologically ineffective IV fluid. This may represent an avenue to improve ED care efficiency.

Keywords: Carotid artery; Doppler ultrasound; Fluid refractory; Fluid responsiveness; Personalized medicine; Quality improvement; Wearable technology.

Fig. 1

The wearable Doppler ultrasound and its interface. A The device on a healthy volunteer. B Carotid Doppler spectra showing calculation of carotid corrected flow time (ccFT) by the equation of Wodey. Velocity is on y-axis in centimeters per second (cm/s) and time on x-axis in seconds (s); heart rate (HR) is calculated from cycle length. C Example of a preload challenge shown on the graphical user interface of the wearable Doppler. Each green bar represents the ccFT of a single cardiac cycle; the y-axis is ccFT in milliseconds and the x-axis is time in seconds

Fig. 2

Distribution of effective and ineffective preload challenges based on ccFT_∆ thresholds determined by Barjaktarevic and colleagues