Hemorrhagic shock hemodynamic and metabolic behavior: experimental study in dogs.

BACKGROUND AND OBJECTIVES Different experimental models have been used to illustrate hemodynamic and metabolic changes during hemorrhagic shock. This study aimed at observing hemodynamic and metabolic behaviors during a sequential and progressive model of hemorrhagic shock in dogs to determine which indices are earlier changed. METHODS The study involved 13 dogs under total intravenous anesthesia with sodium pentobarbital, standard ventilation and previously splenectomized. Animals were not hydrated and bleeding velocity was dictated by animals blood pressure. Evaluated parameters were: hemodynamic (heart rate - HR, mean blood pressure - MBP, systemic vascular resistance index - SVRI, stroke index - SI, cardiac index - CI, shock index - i.Shock, left ventricular stroke work index - LVSWI, pulmonary capillary pressure - PCP, central venous pressure - CVP); and metabolic (mixed venous saturation - SvO2, venous oxygen pressure - PvO2, oxygen transport - O2T, oxygen consumption - VO2, oxygen extraction - TEO2, serum lactate). Results and parameters were evaluated in 6 different moments: M1 - control, and the other moments corresponding to gradual 10% decrease in calculated volume for each animal. RESULTS Hemorrhage has determined significant heart rate decrease in M6 only; MBP, CI, i.Shock, LVSWI decrease in all studied moments; mild CVP and PCP change in all moments; PVO2 and SVO2 decrease in all moments; O2T decrease, VO2 stabilization and TEO2 increase in all moments; shock index was increased from M1 to M3, was decreased in M4 and again increased until M6; SVRI was increased from M1 to M4, remained unchanged in M5 and has significantly decreased in M6; lactate has increased as from M5 and M6. CONCLUSIONS Mean blood pressure, heart rate, central venous pressure and pulmonary capillary pressure have not reflected real volume status of dogs in our experimental model, oxygen transport, consumption and extraction rate are useful parameters to determine hemorrhagic shock reversibility and prognosis.