Comparison of the effects of different dosages of dexamethasone on seawater drowning-induced acute lung injury in rabbits

Objective To explore the desirable dosage of dexamethasone (DM) by comparison of the therapeutic effects of different dosages of DM on the seawater drowning-induced acute lung injury (SWD-ALI) in rabbits. Methods SWD-ALI model was established in twenty-eight healthy New Zealand rabbits, and they were randomly allocated to 4 groups by using a random number table. Animals of D0.5, D1 and D5 group were given DM with the dosage of 0.5, 1 and 5 mg/kg, respectively, while of S group were given on treatment. Respiratory rate and blood gas analysis were recorded before DM administration, the immediately after administration, and 5, 30, 60, 120 and 180 min after giving DM, and the serum level of TNF-α was determined at some of the time points. Total serum proteins were measured, pathologic changes were observed, and wet-to-dry lung weight ratio and lung permeability index were calculated at the termination of the experiment. Results Tachypnea appeared in all the animals after seawater drowning, but spasmodic attacks appeared only in the D5 group. Compared with that of S group, the levels of PaO2, PaCO2 and BE were slightly ameliorated, the total cell counts and the proportion of neutrophil decreased significantly (P0.01), wet-to-dry ratio of lung tissue, lung permeability index, pathologic scores and TNF-α level also decreased remarkably (P0.01) in all the DM treatment groups. Conclusions Dexamethasone, especially in a low dosage, may improve the hypoxemia effectively, ameliorate pulmonary edema and lung injuries, decrease the pulmonary capillary permeability and alleviate inflammatory reaction.