Rapporto tra il diametro della vena cava caudale e dell'aorta (CVC/Ao ratio): studio di un nuovo indice ecografico di volemia e del suo utilizzo come predittore della risposta ai fluidi nel cane

Volemia optimization is crucial for the successful treatment of critical subjects in the intensive care unit (ICU). It is well known that fluids imbalance increased risk of morbidity and mortality. Individualized goal directed fluid therapy is a term used to describe the use of predictors of fluid responsiveness (PFR) to guide fluids administration and to discriminate between who will benefit from a bolus of fluid (responders (R)) from who won’t (non-responders (NR)). In the last decade static or dynamic ultrasound PRFs have been described in humans to guide fluid therapy. Caudal vena cava and aortic diameter ratio (CVC/Ao-ratio) has been also found being highly correlated to volemia in dogs. Aim of the work is to explore diagnostic accuracy of some possible PFR in dogs. Prospective study enrolling ICU dogs, in which a fluid therapy regime had to be planned. Dogs with recognized arrhythmias, cardiac or intrathoracic diseases were excluded. Before and immediately after a mini-bolus of fluids (MBF) administration (4 ml Kg-1 of Ringers’ lactate IV over 60 seconds) the following data were recorded: heart rate (HR); respiratory rate (RR); non invasive blood pressure (NIBP); left ventricle end diastolic diameter (LVEDD in right side short axis parasternal view); velocity time integral of aortic flow (VTI in subcostal view); CVC and Ao transverse us-scanning were recorded by a right lateral intercostal scanning at the level of porta hepatis. Responders had an increased of VTI by of 15% after bolus. The maximal (CVCs-a-max) and the minimal (CVCs-a-min) dimension reached by the short axis of the CVC during the respiratory cycling and the Ao dimension during diastole (Aod) were measured. CVC/AO-ratio was calculated as CVCs-a-max/Aod. CVC collapsibility was measured as: ((CVCs-a-max – CVCs-a-min)/CVCs-a-max)x100). Twenty-one dogs were included: median age 72(12-360)months, median weight 7(1.5-30)kg. Median basal HR and MAP were 124(59-190)bpm and 109(74-160)mmHg. Eight dogs were R and 13 NR. CVCs-a max/Aod ROC=0.84 (0.61-0.96) p=0.0005 cutoff=0.82 (Se=100%; Sp=77%). CVCs-a min/Aod ROC=0.74 (0.50-0.90) p=0.04 cutoff=0.56 (Se=87 %; Sp=54%). EDVI: ROC=0.78(0.55-0.93) (p=0.02) cutoff = 0.55 (Se=75%; Sp=92%). CVC collapsibility ROC=0.51 p=0.94. ROC for multiple indipendent predictors (EDVI and CAVA MAx) is : 0,894 (0,683-0,985) p=0,008. CVCs-a max/Aod and good PFR in dogs. They are simple, reliable, easy to learn methods to guide fluid therapy. CVC collapsibility can not be used as PFR in this specie.