Is there a relationship between the diameter of the inferior vena cava and hemodynamic parameters in critically ill patients?

Influence of the Respiratory Cycle on Caudal Vena Cava Diameter Measured by Sonography in Healthy Foals: A Pilot Study

Background

Intravascular volume assessment in foals is challenging. In humans, intravascular volume status is estimated by the caudal vena cava (CVC) collapsibility index (CVC‐CI) defined as (CVC diameter at maximum expiration [CVC_max] – CVC diameter at minimal inspiration [CVC_min])/CVC_max × 100%.

Hypothesis/Objectives

To determine whether the CVC could be sonographically measured in healthy foals, determine differences in CVC_max and CVC_min, and calculate inter‐ and intrarater variability between 2 examiners. We hypothesized that the CVC could be measured sonographically at the subxiphoid view and that there would be a difference between CVC_max and CVC_min values.

Animals

Sixty privately owned foals <1‐month‐old.

Methods

Prospective study. A longitudinal subxiphoid sonographic window in standing foals was used. The CVC_max and CVC_min were analyzed by a linear mixed effect model. Inter‐rater agreement and intrarater variability were expressed by Bland‐Altman and intraclass correlation coefficients, respectively.

Results

Measurements were attained from 58 of 60 foals with mean age of 15 ± 7.9 days and mean weight of 75.7 ± 17.7 kg. The CVC_max was significantly different from CVC_min (D = 0.515, SE = 0.031, P < 0.001). Inter‐rater agreement of the CVC‐CI differed by an average of −0.9% (95% limits of agreement, −12.5 to +10.7%). Intrarater variability of CVC_max was 0.540 and 0.545, of CVC_min was 0.550 and 0.594, and of CVC‐CI was 0.894 and 0.853 for observers 1 and 2, respectively.

Conclusions and Clinical Importance

These results indicate it is possible to reliably measure the CVC sonographically in healthy foals, and the CVC‐CI may prove useful in assessing the intravascular volume status in hypovolemic foals.