Establishment of Reference Intervals for Caudal Vena Cava-to-Aorta Ratio Measured Ultrasonographically in Healthy Nonsedated Dogs.

The ultrasonographic assessment of the caudal vena cava-to-aorta ratio (CVC:Ao) appears to be a promising method for early recognition of alterations of intravascular volume status in veterinary medicine. The primary objective of this study was to establish the reference intervals of the CVC:Ao ratio with ultrasound in nonsedated healthy dogs. Secondary objectives were to determine the influence of the respiratory cycle and to evaluate correlations between ultrasonographic measurements, signalment and physical exam findings. Ultrasonographic measurements of Ao and CVC diameters were successfully obtained for all sixty dogs included. No evidence of a difference was observed between the measurements of Ao and CVC diameters, and CVC:Ao ratio between inspiration and expiration (P = .373, P = .318, and P = .537, respectively). The reference interval for CVC:Ao ratio (95% CI), generated from US measurements performed at any moment of the respiratory cycle was defined as 0.93 (0.91-0.95) -1.32 (1.30-1.34). The CVC:Ao ratio was significantly negatively correlated with age (r = -0.341, P = .008) and positively correlated with respiratory rate (r = 0.423, P < .001), but not with heart rate (P = .573) or arterial systolic blood pressure (P = .166). A low inter- and intraoperator variability in repeated measurements was observed for each operator and between operators. The ultrasonographic measurement of the CVC:Ao ratio appears as a simple method with low inter- and intraoperator variability using the ultrasonographic protocol described in the current study. With the reference interval established in the present study in healthy nonsedated dogs, further studies should evaluate the utility of this simple method in assessing and monitoring volume status in hypo- and hypervolemic dogs.

Evaluation of the impact of blood donation on tissue perfusion and sublingual microcirculation in dogs: A pilot study.

The objective was to assess the feasibility of the sublingual microcirculation evaluation in dogs by using Sidestream Dark Field (SDF) imaging device and to evaluate the impact of blood donation on sublingual microcirculation and tissue perfusion. Before and after blood sampling, macrocirculatory parameters and tissue perfusion parameters were collected. After quality assessment, four videos per individual and per period were retained for analysis. Data were presented as median (1st quartile - 3rd quartile). The evaluation of the sublingual microcirculation with SDF was feasible in sedated dogs: good quality videos could be recorded in 10/12 dogs (83%). The median blood donation volume was 14 mL/kg (13-15). A significant association between the volume of blood collected and the increase in heart rate was observed: for each milliliter of blood drawn, heart rate increased by 1 bpm (CI95% = [0.2, 2], P = 0.03). Blood collection was associated with a significant increase of shock index (estimate = 0.17, CI95% = [0.02, 0.32], P = 0.04). After blood donation, lactate concentration significantly decreased (before: 2.1 (1.7-2.8), after: 1.1 (0.8-1.7) mmol/l, P = 0.009). No significant variation of the microcirculatory parameters was observed. In conclusion, sublingual evaluation of the microcirculation with SDF technology is feasible in dogs. In the present condition, blood donation did not significantly alter microcirculation. These results need to be confirmed in a larger population.