Feline caudal vena cava-to-aorta ratio and left atrial-to-aortic root ratio increase in acute hypervolemia.

Abstract

OBJECTIVE: To evaluate the caudal vena cava-to-aorta (CVC:Ao) ratio at the hepatorenal location and left atrial-to-aortic root (LA:Ao) ratio as ultrasonographic indicators of acute hypervolemia in cats. METHODS: 10 healthy adult cats underwent general anesthesia with sevoflurane and were experimentally administered incremental volumes of lactated Ringer solution to achieve cumulative blood volume increases of 50%, 100%, 150%, and 200%. Point-of-care ultrasound measurements of the CVC:Ao and LA:Ao ratios were obtained at baseline, following each fluid bolus, and 15 minutes after the final infusion. All measurements were performed in triplicate. RESULTS: Both CVC:Ao and LA:Ao ratios demonstrated increases from baseline at all time points. Following the initial fluid bolus (50% blood volume), the mean CVC:Ao ratio increased by 47% (mean difference, -0.51; 95% CI, -0.74 to 0.28), and the LA:Ao ratio increased by 26% (mean difference, -0.33; 95% CI, -0.58 to 0.07) from baseline. During the redistribution phase (15 minutes following final infusion), the LA:Ao ratio decreased significantly compared to postinfusion values, while the CVC:Ao ratio did not. Intraobserver reliability was good to excellent for the LA:Ao ratio (intraclass correlation coefficient, 0.88; 95% CI, 0.82 to 0.92) and moderate to good for the CVC:Ao ratio (intraclass correlation coefficient, 0.79; 95% CI, 0.70 to 0.86). CONCLUSIONS: The CVC:Ao and LA:Ao ratios increased during acute hypervolemia in cats. The ultrasonographic measurements demonstrated good to excellent intraobserver reliability. The decrease in the LA:Ao ratio during the redistribution phase supports previous findings regarding rapid crystalloid redistribution in cats. CLINICAL RELEVANCE: The CVC:Ao and LA:Ao ratios may serve as useful indicators of volume status in feline patients; however, studies in conscious clinical patients are warranted to further validate these findings in cats.