Context Central venous pressure (CVP) might be used to guide fluid therapy in critically ill patients, but its invasive nature and associated risks have prompted growing interest in non-invasive alternatives such as ultrasonographic vascular indices. Objectives To evaluate the correlation between the caudal vena cava (CVC) to aorta (Ao) (CVC:Ao) ratio and central venous pressure (CVP) and explore the use of this correlation for discriminating CVP values. Materials and methods Intermittent CVP measurements were obtained using a water-filled fluid column in dogs admitted for renal replacement therapy. Low (LCVP), normal (NCVP) and high CVP (HCVP) were defined as values of 0, between 0 and 5, and 5 cmH 2 O (centimeters of water pressure), respectively. The sonographic assessment of volaemia (SAV) protocol was used to obtain the CVC:Ao ratio in the end-expiratory phase. Results Fourteen dogs and 28 CVC:Ao ratio-CVP paired measurements were included. The CVP (in cmH 2 O) was estimated from the CVC:Ao ratio using the generated equation CVP = 20.9*(CVC:Ao)–19.44 ( R = 0.69, p 0.0001). The median CVC:Ao ratios differed significantly among groups at 0.91, 1.00, and 1.12 for LCVP, NCVP and HCVP, respectively ( p = 0.0014). Using a CVC:Ao ratio 0.97, the sensitivity and specificity for detecting LCVP were 87.5 and 72.7%, respectively. Using a CVC:Ao ratio 1.09, the sensitivity and specificity for detecting HCVP were 66.7 and 90.9%, respectively. Clinical significance The CVC:Ao ratio may be used as a surrogate non-invasive marker for estimating CVP in spontaneously breathing dogs. A CVP 0 cmH 2 O is likely if the CVC:Ao ratio is 0.97, and a CVP 5 cmH 2 O is likely if the ratio is 1.09.
Cambournac et al. (Mon,) studied this question.