Effect of Volume Depletion and Intravascular Volume Overload on Ultrasonographically Derived Caudal Vena Cava Parameters in Healthy Sedated Cats.

Abstract

Objective: To sonographically assess caudal vena cava (CVC) and focused cardiac ultrasound (FCU) parameters for volume depletion (VD) and intravascular volume overload (IVVO) in healthy cats.

Design: Prospective, randomized, blinded, crossover study.

Setting: Experimental.

Animals: Twenty-nine healthy research-purposed cats.

Interventions: The VD group received 2 mg/kg furosemide IV every 30-60 min over 6 h, followed by 10 mL/kg isotonic crystalloid or tetrastarch given over 10 min. The IVVO group did not receive furosemide and was administered 30 mL/kg isotonic crystalloid over 10 min. Ultrasonographic images of the CVC (subxiphoid view) and heart (right parasternal short-axis view) were recorded and subjectively evaluated by an operator in real time from both groups at baseline (T0), after furosemide/6 h (T1), and after fluids (T2). CVC inspiratory (CVC_insp) and expiratory (CVC_exp) diameters, CVC collapsibility index (CVC_CI), left atrium-to-aorta ratio (LA:Ao), and left ventricular internal diameter in systole (LVIDs) and diastole (LVIDd) were measured and subjectively graded post hoc by two blinded raters (different to the operator) for CVC parameters; one blinded rater evaluated FCU parameters.

Measurements and main results: In the VD group, CVC_insp (p = 0.004), CVC_exp (p = 0.008), LVIDs (p < 0.001), and LVIDd (p < 0.001) were smaller after administration of furosemide. In the IVVO group, CVC_insp (p = 0.02), CVC_exp (p = 0.04), LVIDs (p < 0.001), and LVIDd (p = 0.001) were larger after fluid administration. The LA:Ao ratio was not different in any group at any time. Intrarater and interrater reliability were moderate to poor. Subjective CVC and FCU assessments were consistent with objective measurements.

Conclusions: Experimentally induced VD and volume overload result in sonographically detectable changes in the CVC_insp and CVC_exp diameters and LVIDs and LVIDd of cats, suggesting the assessment of these parameters may have value in the clinical setting.