Acute blood loss and pulmonary host defense mechanisms in the rat

Water deprivation and food restriction on pulmonary bacterial defenses in mice

Mice deprived of water for 48 hr, mice allowed water but restricted in food intake to equal that consumed by the water-deprived mice, and control mice were exposed for 30 min to an aerosol of Serratia marcescens. Comparison of the number of organisms in the lungs of mice killed immediately after infection and those killed 4 hr later showed a normal reduction over the 4-hr period in the control mice. A significant increase, however, was observed in the water-deprived mice and an even greater increase in the food-restricted mice allowed water. The results did not correlate directly with the lung weight or lung water content. This reduction in bacterial defense could not be assigned solely to either water or food restriction.

Aspiration of blood and pulmonary host defense mechanisms

The effect of aspiration of blood on pulmonary host defenses was studied in the rat. Sham and experimental rats had 0.2 ml of saline or blood/100 g body weight injected into their tracheas. One or 24 hours after aspiration rats were challenged with aerosolized, radiolabeled ((32)P), S. aureus. Fourteen hours after bacterial challenge, lungs were removed and intrapulmonary bacterial inactivation was quantified. Significant impairment of bacterial inactivation occurred at both 15 and 38 hours after aspiration of blood, but not after saline. The pulmonary consolidation after aspiration of blood was focal in nature. The lung weight increased but fractional water content decreased. Arterial pH, pCO(2), or pO(2) were unaffected by aspiration of blood. The number and viability of macrophages recovered by lavage were similar in control, sham and experimental groups. If similar impairment in pulmonary host defenses occurred in man following aspiration of blood, the patient with aspiration of blood would have an increased susceptibility to bacterial infection.