Ultrasonographically derived caudal vena cava parameters acquired in a standing position and lateral recumbency in healthy, lightly sedated cats: a pilot study

Abstract

Objectives The aim of this study was to determine the feasibility of ultrasonographically measuring the caudal vena cava (CVC) at the subxiphoid view of healthy, lightly sedated cats in a standing position and lateral recumbency. Methods This was a prospective, observational, experimental single-centre study. Twenty healthy research-purposed cats were enrolled. Two trained operators scanned each cat in two positions – standing and lateral recumbency – in a randomised order. CVC diameter was measured at the narrowest diameter during inspiration and at the widest diameter during expiration, at two anatomical locations along the CVC – where the CVC crosses the diaphragm (base) and 2 mm caudal to the diaphragm. The CVC collapsibility index (CVC-CI) was calculated for each site. Normalcy was assessed with a Shapiro–Wilk test. A one-way ANOVA with post-hoc Tukey’s test was used to compare inspiratory with expiratory values within and between groups. A paired t-test compared the CVC-CI between groups ( P ⩽0.05 indicated statistical significance). Spearman’s correlation and Bland–Altman analysis assessed inter-operator variability. Results All ultrasonographic data passed normalcy and were reported as mean ± SD. When compared with each other, inspiratory and expiratory values were statistically different for position, location and operator (all P <0.0001). There was no statistically significant difference between lateral recumbency or standing position for inspiratory, expiratory and CVC-CI values. Inter-operator variability was substantial, with operator 2 consistently obtaining smaller measurements than operator 1. The mean CVC-CI in lateral recumbency at the base was 24% for operator 1 and 37% for operator 2. For the same site in standing position, CVC-CI was 27% and 41% for operators 1 and 2, respectively. Conclusions and relevance This pilot study demonstrates that it is possible to ultrasonographically measure the CVC diameter in both lateral recumbency and a standing position in healthy, lightly sedated cats. However, measurements obtained are operator dependent with variability between individuals. Further studies are needed to determine if ultrasonographic CVC assessment will prove helpful in estimating intravascular volume status in cats.

Ultrasonographical Assessment of Caudal Vena Cava Size through Different Views in Healthy Calves: A Pilot Study

“…Sometimes the power of the probe was not sufficient to access the CVC when the thorax was deeper than 20 cm. This result shows that, contrary to what has been described in other species [ 18 , 20 ], the subxiphoid site could not be used as a reliable tool to ultrasonographically evaluate CVC in calves. However, evolution over time of the percentage (%) of interpretable views realized at the subxiphoid site in calves in the first part of the protocol shows that the technical ability to evaluate CVC at this site could improve with practice ( Figure 5 ).…”

“…In companion animal medicine, several studies have described the ultrasonographic assessment of the caudal vena cava diameter (CVC D ) at different locations as an inexpensive, rapid, and noninvasive marker for the assessment of intravascular volume status [ 9 , 16 , 17 , 18 , 19 , 20 ]. Different sites to perform caudal vena cava (CVC) measurements have been described in different species, and CVC D is often expressed as a ratio to the aortic diameter (Ao D ) to compensate for variations in body size [ 16 ].…”

Establishment of reference intervals for ultrasonographically derived caudal vena cava parameters from 110 healthy, lightly sedated cats

“…19 Similarly, a recent pilot study in 20 cats evaluating CVC parameters in lateral and standing positions showed a poor inter-operator reliability for both CVC diameter and CVCCI. 24 In dogs, one study establishing RIs for CVC parameters also reported poor intra-rater reliability for the CVCCI obtained from the subxiphoid window. 25 A likely reason for the poor reliability is that the CVCCI is a generated variable, and multiplicative augmentation in diameter differences will lower the reliability compared with individual diameter measurements.…”

“…In spontaneously breathing cats, the abdominal portion of the CVC collapses during inspiration. 24,34 This is owing to increased negative intrathoracic pressure during inspiration and a consequent decrease of right atrial and right ventricular pressure. Concurrently, inspiration also increases the abdominal pressure, creating a gradient that shifts blood from the abdominal portion of the CVC into the thoracic portion, augmenting venous return to the heart.…”

“…20 The feasibility of obtaining ultrasonographically derived CVC parameters has been established in cats, foals, calves and dogs, with reference intervals (RIs) established in dogs. [23][24][25][26] To determine whether CVC parameters can be used as a tool to assess IVVS and guide IVF administration in sick cats, RIs from healthy cats are needed.…”