Conventional vs. Advanced Echocardiographic Parameters for Predict Fluid Responsiveness in Healthy Dogs

Abstract

Background: Volume replacement is considered an essential component in the treatment of critically ill patients, but excess fluid administration can be as harmful as the lack of fluid therapy. Therefore, the volume replacement is only beneficial in patients deemed to be fluid responsive, that is, when the individual has an increase in their stroke volume after administration of a volume challenge. This study aim to assess whether conventional and advanced echocardiographic parameters for assessing left ventricular systolic function are able to predict fluid responsiveness in healthy spontaneously breathing dogs. The hypothesis was that some of these parameters would differ between responsive and non-responsive animals and could be used as a complementary measure for assessment of fluid responsiveness.
Materials, Methods & Results: A prospective study was carried out in which 22 client-owned healthy dogs over 1 year of age that presented to the Veterinary Medical Teaching Hospital for elective neutering procedure were included. All dogs underwent conventional and advanced echocardiographic examination to obtain the left ventricular internal diameter in diastole normalized (LVIDDn), left ventricular internal diameter in systole normalized (LVIDSn), ejection fraction (EF) and shortening fraction (SF) according to the Teischholz methodology, global longitudinal strain (GLS) and tissue motion annular displacement (TMAD). There parameters were evaluated before and after administration of a volume challenge with 10 mL/kg lactate ringer intravenously for 20 min. Based on the variation in aortic velocity integral time, 31.82% of dogs were considered responsive and 68.18% were non-responsive to the volume challenge. For advanced echocardiography, TMAD indexed by body weight (mm/kg) > 0.89 (P = 0.004) and body surface area (mm/m²) >18.9 (P = 0.004) after volume challenge had the best area under the curve values (both 0.895) and smaller gray zone intervals (0.52 - 0.81 and 14.89 - 17.88) for the identification of responsive dogs. Although, TMAD (mm/kg and mm/m2) before volume challenge was also higher in the responsive dogs (P = 0.041 and P = 0.029). As for conventional echocardiography, the LVIDDn < 1.39 (P = 0.003) before volume challenge had the best area under the curve value (0.866) and the smallest gray zone interval (1.4 - 1.57) for the identification of responsive dogs. The GLS and the TMAD in milimeters (mm), percentage (%) and indexed by cubic root of weight (mm/∛kg) did not differ between the responsive and non-responsive dogs before and after volume challenge.
Discussion: TMAD indexed by body weight (mm/kg) and body surface area (mm/m2) before and after volume challenge and the LVIDDn before volume challenge may be useful measures to complement the assessment of fluid responsiveness in spontaneously breathing dogs. This is the first study to use TMAD as a predictive parameter for fluid responsiveness in healthy, spontaneously breathing, dogs. Even it is an advanced echocardiographic technique, TMAD has advantages in
terms of execution time and the fact that it is less dependence on image quality or operator experience. It is possible that in the future such variables may form a useful part of the evaluation of fluid responsiveness in dogs. However, more studies are needed to better understand the applicability of these techniques, especially in dogs with hemodynamic changes.

Keywords: canine, global longitudinal strain, stroke volume, tissue motion annular displacement, TMAD, VTI.