Mechanical ventilation affects alveolar fibrinolysis in LPS-induced lung injury.

The aim of the present study was to determine the effects of mechanical ventilation on alveolar fibrin turnover in lipopolysaccharide (LPS)-induced lung injury. In a randomised controlled trial, Sprague-Dawley rats (n=61) were allocated to three ventilation groups after intratracheal LPS (Salmonella enteritidis) instillations. Group I animals were subjected to 16 cmH(2)O positive inspiratory pressure (PIP) and 5 cmH(2)O positive end-expiratory pressure (PEEP); group 11 animals to 26 cmH(2)O PIP and 5 cmH(2)O PEEP; and group III animals to 35 cmH(2)O PIP and 5 cmH(2)O PEEP. Control rats (not mechanically ventilated) received LPS. Healthy rats served as a reference group. Levels of thrombin-antithrombin complex (TATc), D-dimer, plasminogen activator inhibitor (PAI) activity and PAI-1 antigen in bronchoalveolar lavage fluid were measured. LPS-induced lung injury increased TATc, D-dimer and PAI activity and PAI-1 antigen levels versus healthy animals. High pressure-amplitude ventilation increased TATc concentrations. D-dimer concentrations were not significantly raised. Instead, PAI activity increased with the amplitude of the pressure, from 0.7 U-mL(-1) in group I to 3.4 U-mL(-1) in group II and 5.0 U-mL(-1) in group III. There was no change in PAI-1 antigen levels. In conclusion, mechanical ventilation creates an alveolar/pulmonary anti-fibrinolytic milieu in endotoxin-induced lung injury which, at least in part, might be due to an increase in plasminogen activator inhibitor activity.