Cardiac variation of inferior vena cava: new concept in the evaluation of intravascular blood volume

Abstract

Evaluation of the intravascular blood volume is an important assessment in emergency and critical care medicine. Measurement of the inferior vena cava (IVC) respiratory variation by ultrasound echography is useful, but it entails subjective problems. We have hypothesized that IVC cardiac variation is also correlated with intravascular blood volume and analyzed it automatically using computer software of two kinds, later comparing the results. Snakes, software to track boundaries by curve line continuity, and template matching software were incorporated into a computer with an ultrasound machine to track the short-axis view of IVC automatically and analyze it with approximation by ellipse. Eight healthy volunteers with temporary mild hypovolemia underwent echography before and after passive leg raising and while wearing medical anti-shock trousers. IVC cardiac variation was visually decreased by both leg raising and medical anti-shock trousers. The collapse index (maximum - minimum/maximum) of area during three cardiac beats was decreased showing a good relationship to fluid load simulations; 0.24 ± 0.03 at baseline versus 0.11 ± 0.01 with leg raising and 0.12 ± 0.01 with medical anti-shock trousers. In conclusion, IVC cardiac variation has the potential to provide an evaluation of water volume. It presents some advantages in mechanical analysis over respiratory variation. At the very least, we need to exercise some caution with cardiac variation when evaluating respiratory variation.

Semi-automated Tracking and Continuous Monitoring of Inferior Vena Cava Diameter in Simulated and Experimental Ultrasound Imaging

“…In addition, this could provide increased information of possible clinical relevance: the cardiac oscillation is expected to essentially reflect the compliance of the IVC, which, in turn, reflects the extent of filling of the vascular system; on the other hand, the respiratory oscillation depends on IVC compliance and the amplitude and type of respiration (thoracic or diaphragmatic) (Kimura et al 2011). A recent study investigating the cardiac component during short apnea seems to support this hypothesis (Nakamura et al 2013). New studies based on the present approach may elucidate the different functional significance of cardiac and respiratory rhythms in IVC diameter.…”

“…The two frames presented correspond to the moment at which the diameter estimation is either maximally positive or negative. 854 Ultrasound in Medicine and Biology Volume 41, Number 3, 2015 (Nakamura et al 2013). The asynchronous summation of the two components introduces variability into the maximum and minimum diameters measured at each respiratory cycle, which, in turn, produces uncertain estimates of the CI.…”

“…To avoid respiration-related movements, in a recent study the recordings were performed on patients maintaining a short apnea, thus limiting analysis of oscillations to the cardiac component (Nakamura et al 2013). Another possibility is to manually make single measurements at the same location using B-mode cine loops rather than Mmode (Lyon et al 2005;Wallace et al 2010).…”

Prospective analysis of cardiac collapsibility of inferior vena cava using ultrasonography

“…Furthermore, results of our pilot study of healthy volunteers suggest that IVC cardiac variation decreases by leg raising in a supine position, which means that it apparently correlates negatively with CVP or intravascular volume [8]. However, that study did not analyze the relation between respiratory and cardiac variation.…”

Vena Cava Responsiveness to Controlled Isovolumetric Respiratory Efforts

“…Several factors, mostly related to the variability of spontaneous breathing, may affect assessment of the CI and potentially undermine its reliability: (1) spontaneous breathing is intrinsically irregular in both amplitude and frequency and is affected by emotional status, pain, and pathology; (2) the respiratory pattern changes depending on gender and age, also in terms of its thoracic/diaphragmatic components, which affect in different ways the abdominal pressure and IVC diameter; (3) the IVC moves considerably during respiration, introducing errors in the assessment of CI, unless some advanced image analysis is implemented; (4) often, the cross section of the IVC is not circular, and may exhibit anisotropic changes in size as a result of modifications of filling pressure or breathing . Consequently, the arbitrary choice of a given section for the measurement of IVC diameter may not be adequate to assess changes in its size and pulsatility, and the evaluation of the whole cross‐sectional area (CSA) has instead been proposed …”