E. Jalava, R. Niskanen, J. Laurila, T. O. P. Leppäluoto, K. M. Kuusela, J. L. Raekallio
Background
In critical care, central venous pressure (CVP) is a key indicator of intravascular volume status, but its invasive nature has prompted the use of non-invasive surrogates like inferior vena cava (IVC) collapsibility. While IVC measurements are well-studied in humans, their reliability in veterinary patients under varying volume conditions is uncertain. This study evaluated how volume depletion and overload affect the relationship between IVC collapsibility and CVP in anesthetized dogs.
Methods
Six healthy adult Beagle dogs were anesthetized with propofol and isoflurane. Volume depletion was induced by controlled hemorrhage, followed by volume restoration and subsequent volume overload through crystalloid infusion. CVP was measured via a jugular catheter, and IVC diameter changes were monitored ultrasonographically to calculate the collapsibility index (IVC-CI). Correlations between IVC-CI and CVP were assessed under each volume state using repeated-measures analysis.
Results
During normovolemia, a strong inverse correlation was observed between IVC-CI and CVP (r = –0.84, P < 0.01). However, this relationship weakened markedly during both volume depletion and overload, with IVC-CI failing to predict CVP accurately in extreme conditions. Volume overload led to significant IVC distension with reduced collapsibility, while hemorrhagic depletion produced high collapsibility but inconsistent CVP readings due to compensatory mechanisms.
Limitations
The study’s small sample size (n = 6) and use of healthy, anesthetized dogs limit extrapolation to clinical patients with concurrent disease. Anesthesia may have influenced venous tone and IVC dynamics. Additionally, only acute volume changes were evaluated without long-term assessment of compensatory fluid redistribution.
Conclusions
IVC collapsibility correlates with CVP only under normovolemic conditions and becomes unreliable during marked hypovolemia or hypervolemia. The findings caution against relying solely on IVC-CI for volume assessment in anesthetized or critically ill dogs. Direct CVP measurement remains essential when precise intravascular volume evaluation is required.
Schematic illustration of the heart from the right parasternal short axis view. (A) LVIDd (mm). (B) LVIDs (mm) measured at the level of the papillary muscles (pink arrows). (C) LA and Ao diameters (mm) measured at the level of the closed aortic valve (blue arrows). (D) Ao-in-LA grade determined by the number of Ao circumferences that fit in the LA (blue circles). Ao, aorta; Ao-in-LA, aorta-in-left atrium; LA, left atrium; LVIDd, left ventricular internal diameter (mm) in diastole; LVIDs, left ventricular internal diameter (mm) in systole.
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