Reza Azargoun - Graduated of Small Animal Internal Medicine, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
Reza Avizeh - Department of Clinical Sciences, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
Alireza Ghadiri - Department of Clinical Sciences, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
Hadi Imani Rastabi - Department of Clinical Sciences, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
Mahdi Pourmahdi - Department of Food Hygiene, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran.

Objective- The aim of this study was to assess ultrasonography-derived caudal vena cava to aorta ratio (CVC/Ao) as a novel endpoint in the resuscitation of experimental hemorrhagic shock in dogs.Design- Experimental study.Animals- Ten adult mongrel healthy dogs.Procedures- After induction of anesthesia (control assessments), hemorrhagic shock was induced by blood withdrawal to a mean arterial pressure of ۴۰ to ۵۰ mmHg within ۳۰ minutes and then maintained in a hypovolemic situation for an additional ۳۰ minutes (second and third stages of assessments). Afterward, the dogs were randomly assigned to two groups which received ۲۰ ml/kg lactated Ringer's solution or ۵ ml/kg Hydroxyethyl starch, in four consecutive ۱۵ minutes intervals (fourth stage of assessments). One hour after the last resuscitation step, final ultrasonographic assessments were performed.Results- Hemorrhagic shock caused a significant decrease in the CVC and Ao diameters as well as the CVC/Ao (۲.۱۴ ± ۰.۲۸ cm, ۰.۸۵ ± ۰.۰۷ cm and ۰.۴ ± ۰.۰۶, respectively) (p<۰.۰۵). Following the fluid resuscitation, CVC/Ao increased and returned to pre-shock values in both groups.Conclusion and clinical relevance- Findings indicated that serial ultrasonographic assessment of the CVC/Ao can be a useful endpoint in the resuscitation of dogs with hemorrhagic shock.

Ultrasonography, caudal vena cava to aorta ratio, Hemorrhagic shock, Dog