Effects of Hypovolemia and Volume Overload on Ultrasonographically Derived Caudal Vena Cava Parameters in Healthy Lightly Sedated Cats
Introduction
This study investigated the effect of hypovolemia and volume overload on ultrasonographically derived caudal vena cava (CVC) parameters in healthy, lightly sedated cats.
Methods
Randomized, blinded, prospective, cross-over study involving 14 healthy cats assigned to a hypovolemia or volume overload group with a 7-day washout period. The hypovolemia group received furosemide; 2 mg/kg IV every 30 to 60 minutes up to 14 mg/kg or 10% weight loss was achieved. Lactated Ringer’s or hydroxyethyl starch (130/0.4) at 10 ml/kg IV was then administered over 10 mins. The volume overload group received 30 ml/kg of IV lactated Ringer’s over 10 min. Both groups had subxiphoid sonographic CVC parameters measured at three timepoints—T0 (baseline), T1 (hypovolemia or pre-volume overload, respectively) and T2 (post-fluid challenge or volume overload, respectively) by a blinded operator. CVC measurements were obtained at the narrowest inspiratory and widest expiratory diameter (CVCinsp, CVCexp, respectively) where the CVC crosses the diaphragm, and the collapsibility index (CVC–CI) was calculated from recorded cineloops by a blinded rater. A Shapiro-Wilk test was used to assess normalcy and a one-way ANOVA was used to compare groups at different time points. A p-value ≤0.05 was considered significant.
Results
All data passed normalcy. There was a significant difference between CVCinsp and CVCexp at each time point (p<0.0001). CVCexp values were statistically different between baseline and volume overload (3.02 mm ±1.00, 4.17 mm ±0.62, respectively, p<0.001). There were no statistically significant differences between CVCinsp, CVCexp, and CVC–CI values between any time points that were measured on the same day.
Conclusion
These preliminary results suggest that compared to CVC–CI and CVCinsp, CVCexp measurements may be more sensitive at predicting volume status in cats, particularly volume overload. However, the sample size is small and further research is needed to assess the utility of all CVC parameters to estimate volume status in cats.
E-mail: s.jalava@massey.ac.nz