Tidal volume in animal models of hemorrhagic and endotoxic shock

The aim of this study was to examine the characteristics of lung, kidney and small intestine injury caused by early resuscitation from hemorrhagic shock (HS) and endotoxic shock (ES) when ventilating with different tidal volumes (Vts). The study also considered the determination of the appropriate Vt for use in mechanical ventilation (MV) during treatment for shock. Resuscitated rabbits were ventilated with varying Vts for 120 min following 60 min of HS or ES. The histopathology, ultrastructure and apoptotic index (AI) of the lung, kidney and small intestine were then measured. Organs from the high-Vt groups (VT=12-15 ml/kg) showed the highest pathological scores (PSs; P<0.05). For HS, the renal PS and AI of the HS-M group (Vt=8-10 ml/kg)were lower than those of the HS-L group (Vt=4-6 ml/kg) and the lung PS and AI of the HS-C (control) group were lower compared with those of the HS-M group. For ES, the lung PS of the ES-L group was lower compared with that of the ES-M group (Vt=8-10 ml/kg) and the lung AI of the ES-C (control) group was lower compared with that of the ES-L group (Vt=4-6 ml/kg). When ventilated with the same Vt, ES resulted in higher PSs in the lung and intestine and a lower renal PS (P<0.05) than HS. MV was not recommended for either shock type. When it was necessary for MV to be applied, low Vt (4-6 ml/kg) protected the lung in ES. Moderate Vt (8-10 ml/kg) may be relatively safe to use for HS.