Excessive NO has been shown to play a major role in the pathogenesis of multiple organ dysfunctions in septic condition.
Burn injury, especially if it is associated with
smoke inhalation, is often complicated by subsequent development of
pneumonia or
sepsis that determine the outcome. In the present study, we developed an ovine
sepsis model, created by exposing sheep to
smoke inhalation followed by instillation of bacteria into the airway, that closely mimics human
sepsis and
pneumonia. We hypothesized that the inhibition of iNOS-derived excessive NO might be beneficial in treating the cardiopulmonary derangement in this model. Female sheep (n = 18) were surgically prepared for the study and given a
tracheostomy. This was followed by insufflation of 48 breaths of cotton
smoke (< 40 degrees C) into the airway of each animal and subsequent instillation of live Pseudomonas aeruginosa (5 x 10(11) colony forming units) into each sheep's lung. All sheep were mechanically ventilated using 100% O2. Continuous infusion of BBS-2 (100 microg/kg/h), an iNOS inhibitor, was started 1 h after insult. The administration of BBS-2 improved pulmonary gas exchange (PaO2/FiO2 and pulmonary shunt fraction) and partially reduced
airway obstruction and an increase in ventilatory pressures. The lung water content was not affected by iNOS inhibition. The
hypotension seen in nontreated animals was not ameliorated either. The increase in plasma concentration of
nitrate and
nitrite was inhibited by BBS-2. The results of present study show that iNOS may be partially involved in the pathogenesis of
acute lung injury induced by
smoke inhalation followed by bacterial instillation in the airway.