Ischemia and reperfusion increases susceptibility to ventilator-induced lung injury in rats

Objectives: Hemorrhagic shock followed by resuscitation (HSR) commonly triggers an inflammatory response that leads to acute respiratory distress syndrome. Hypothesis: HSR exacerbates mechanical stress-induced lung injury by rendering the lung more susceptible to ventilator-induced lung injury. Methods: Rats were subjected to HSR, and were randomized into an HSR + high tidal volume and zero positive end-expiratory pressure (PEEP) or a HSR + low tidal volume with 5 cm H₂O PEEP. A sham-operated rat + high tidal volume and zero PEEP served as a control. Results: HSR increased susceptibility to ventilator-induced lung injury as evidenced by an increase in lung elastance and the wet/dry ratio and a reduction in Pa_O2 as compared with the other groups. The lung injury observed in the HSR + high tidal volume group was associated with a higher level of interleukin 6 in the lung and blood, increased epithelial cell apoptosis in the kidney and small intestine villi, and a tendency toward high levels of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and creatinine in plasma. Conclusions: HSR priming renders the lung and kidney more susceptible to mechanical ventilation-induced organ injury.