Effects of atelectatic areas on the surrounding lung tissue during mechanical ventilation in an experimental model of acute lung injury induced by lipopolysaccharide

OBJECTIVE

To assess the effect of atelectasis during mechanical ventilation on the periatelectatic and normal lung regions in a model of atelectasis in rats with acute lung injury induced by lipopolysaccharide.

METHODS

Twenty-four rats were randomized into the following four groups, each with 6 animals: the Saline-Control Group, Lipopolysaccharide Control Group, Saline-Atelectasis Group, and Lipopolysaccharide Atelectasis Group. Acute lung injury was induced by intraperitoneal injection of lipopolysaccharide. After 24 hours, atelectasis was induced by bronchial blocking. The animals underwent mechanical ventilation for two hours with protective parameters, and respiratory mechanics were monitored during this period. Thereafter, histologic analyses of two regions of interest, periatelectatic areas and the normally-aerated lung contralateral to the atelectatic areas, were performed.

RESULTS

The lung injury score was significantly higher in the Lipopolysaccharide Control Group (0.41 ± 0.13) than in the Saline Control Group (0.15 ± 0.51), p < 0.05. Periatelectatic regions showed higher lung injury scores than normally-aerated regions in both the Saline-Atelectasis (0.44 ± 0.06 x 0.27 ± 0.74 p < 0.05) and Lipopolysaccharide Atelectasis (0.56 ± 0.09 x 0.35 ± 0.04 p < 0.05) Groups. The lung injury score in the periatelectatic regions was higher in the Lipopolysaccharide Atelectasis Group (0.56 ± 0.09) than in the periatelectatic region of the Saline-Atelectasis Group (0.44 ± 0.06), p < 0.05.

CONCLUSION

Atelectasis may cause injury to the surrounding tissue after a period of mechanical ventilation with protective parameters. Its effect was more significant in previously injured lungs.

[The weight of the spleen in chronic chagasics]

During the course of systemic inflammatory reactions and chronic venous congestion, the documented phenomenon of increased spleen size is respectively called reactional hyperplasia and congestive splenomegaly. In Chagas' disease, the inflammatory process observed in the heart of chronically infected patients can result in heart failure and ultimately in congestive failure. In order to evaluate the spleen response to both inflammatory and cardiac processes, in this retrospective study we compare the weight of spleens from normal and chagasic patients, with or without congestive failure. Information about patient age, sex, race and spleen weight was collected from autopsy reports. Eighty-eight selected cases were divided into four groups: 1) chagasic patients with congestive failure, 2) chagasic patients without congestive failure, 3) non-chagasic patients with congestive failure, 4) non-chagasic patients without congestive failure. The average age was 44.9 +/- 15.4 years, 53.4% were Caucasians and 70.5% were males, and no significant difference in these parameters was observed between the four groups. The spleen weight for the groups presenting congestive failure was 183.7 +/- 85.9 g for chagasic and 206.3 +/- 101.0 g for non-chagasic patients; for the groups without congestive failure the average spleen weight was 173.7 +/- 118.9 g for the chagasic and 117.2 +/- 52.0 g for non-chagasic patients. The spleen weight was significantly higher for the chagasic patients without congestive failure when compared to the non-chagasic group without congestive failure. These results suggest that the inflammatory component in Chagas' disease plays an important role in the increase of spleen weight together with hemodynamic alterations arising from congestive heart failure.

Gastroesophageal varices: prevention of bleeding and rebleeding

Nonselective beta-adrenergic blockers (propranolol and nadolol) are effective in preventing initial variceal hemorrhage, although their influence on improving survival is less dramatic. There is no role for either sclerotherapy or prophylactic portosystemic shunts for the prevention of initial variceal hemorrhage. Both endoscopic therapy (sclerotherapy, esophageal variceal ligation) and nonselective beta-adrenergic blockers are effective in reducing the risk of recurrent bleeding related to portal hypertension; however, there are significant numbers of failures with both approaches, and the effect on survival is less impressive. Randomized controlled trials evaluating each of these therapeutic options are reviewed in this article.