The effects of synchronized intermittent mandatory ventilation (SIMV) versus volume assured pressure support ventilation (VAPSV) on cardiorespiratory parameters in propofol-anesthetized rabbits induced to acute hypovolemia were evaluated. Twenty New Zealand white rabbits were randomly allotted to: GM under SIMV and GV under VAPSV. In premedication, ketamine (15mg/kg) and xylazine (1mg/kg) were administered intramuscularly. Propofol was used to induce (8mg/kg) and to maintain anesthesia (0.5mg/kg/min). Following, according to each group, the ventilation mode was started. After thirty minutes of anesthesia induction, rabbits were induced to hypovolemia by removing 12ml/kg of arterial blood. The initial measurement of parameters (M0) was recorded thirty minutes after anesthesia induction. Additional recordings were performed at 10-minute intervals after hypovolemia induction (M1 to M6). Cardiac output (CO) was bigger in GM. In both groups, arterial pressures and central venous pressure (CVP) decreased from M1, while arterial partial pressure of oxygen (PaO2) increased from M4. The respiratory effort was greater in GV at all times studied. In conclusion, VAPSV and SIMV were safe for arterial oxygenation and provided adequate gas exchange. However, the SIMV is more appropriate for hypovolemic rabbits, because it maintains hemodynamic stability and promotes lower respiratory work.
rabbits; hypovolemia; intravenous anesthesia; mechanical ventilation
