The assessment of circulating volume using inferior vena cava collapse index and carotid Doppler velocity time integral in healthy volunteers: a pilot study.

Tom Peachey,Elinor C Baker,Andrew Tang,Tim Harris,Yonathan Freund,Jason Pott

doi:10.1186/s13049-016-0298-0

Abstract

BackgroundAssessment of circulating volume and the requirement for fluid replacement are fundamental to resuscitation but remain largely empirical. Passive leg raise (PLR) may determine fluid responders while avoiding potential fluid overload. We hypothesised that inferior vena cava collapse index (IVCCI) and carotid artery blood flow would change predictably in response to PLR, potentially providing a non-invasive tool to assess circulating volume and identifying fluid responsive patients.MethodsWe conducted a prospective proof of concept pilot study on fasted healthy volunteers. One operator measured IVC diameter during quiet respiration and sniff, and carotid artery flow. Stroke volume (SV) was also measured using suprasternal Doppler. Our primary endpoint was change in IVCCI after PLR. We also studied changes in IVCCI after “sniff”, and correlation between carotid artery flow and SV.ResultsPassive leg raise was associated with significant reduction in the mean inferior vena cava collapsibility index from 0.24 to 0.17 (p < 0.01). Mean stroke volume increased from 56.0 to 69.2 mL (p < 0.01). There was no significant change in common carotid artery blood flow. Changes in physiology consequent upon passive leg raise normalised rapidly.DiscussionPassive leg raise is associated with a decrease of IVCCI and increase in stroke volume. However, the wide range of values observed suggests that factors other than circulating volume predominate in determining the proportion of collapse with respiration.ConclusionIn contrast to other studies, we did not find that carotid blood flow increased with passive leg raise. Rapid normalisation of post-PLR physiology may account for this.

Highlights

Assessment of circulating volume and the requirement for fluid replacement are fundamental to resuscitation but remain largely empirical
This demonstrates that stroke volume increases with passive leg raise as a consequence of increased central volume loading
The data shows that inferior vena cava collapse index (IVCCI) reduces and stroke volume increases with passive leg raise, there is poor correlation between IVCCI and stroke volume changes – inferior vena cava (IVC) collapsibility does not predict the subjects in which fluid redistribution improves stroke volume

Summary

Introduction

Assessment of circulating volume and the requirement for fluid replacement are fundamental to resuscitation but remain largely empirical. We hypothesised that inferior vena cava collapse index (IVCCI) and carotid artery blood flow would change predictably in response to PLR, potentially providing a non-invasive tool to assess circulating volume and identifying fluid responsive patients. Accurate assessment of circulating volume is challenging in the acute setting. Healthy adults may lose up to 30 % of their circulating volume with little change in their vital signs [2]. Clinical parameters may be abnormal for reasons other than changes in circulating blood volume, such as tachycardia secondary to pain, or altered physiology due to medication [3]. Defining the volume and rate of fluid administration remains largely empirical, despite its fundamental importance in patient care

Objectives

Methods

Results

Discussion

Conclusion