Ischaemia is a common clinical event leading to local and remote injury. Evidence indicates that tissue damage is largely caused by activated neutrophils which accumulate when the tissue is reperfused. If the area of ischaemic tissue is large, neutrophils also sequester in the lungs, inducing non-cardiogenic pulmonary oedema. Ischaemia reperfusion injury is initiated by production of reactive oxygen species which initially appear responsible for the generation of chemotactic activity for neutrophils. Later, once adherent to endothelium, neutrophils mediate damage by secretion of additional reactive oxygen species as well as proteolytic enzymes, in particular elastase. Therapeutic options for limiting ischaemia reperfusion injury include inhibition of oxygen radical formation, pharmacological prevention of neutrophil activation and chemotaxis, and also the use of monoclonal antibodies which prevent neutrophil-endothelial adhesion, a prerequisite for injury.

The treatment of septic shock remains a major problem in surgical practice. Current research on the pathogenesis of the sepsis syndrome focuses on the effects of the lipopolysaccharide constituents of bacterial endotoxin. Evidence suggests that endotoxin induces a whole-body inflammatory response that in turn mediates organ damage, eventually leading to multiorgan failure. The first organ in which failure is usually apparent is the lung, with the appearance of non-cardiogenic pulmonary oedema as part of the adult respiratory distress syndrome. Inflammatory cells involved in lung injury include neutrophils and macrophages, which release mediators such as elastase, oxygen radicals and cytokines. This review summarizes current experimental work on how endotoxin leads to lung injury, based on its effects in animals and patients. Present knowledge suggests that future treatment of septic shock might involve inhibiting the body's inflammatory response to endotoxin. Possible ways of doing this are discussed.

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Hindlimb ischemia and reperfusion lead to lung injury dependent on activated polymorphonuclear neutrophils (PMN) adherence. This study tests whether elastase and oxygen radicals participate in PMN-induced injury once they have become sequestered in lungs. Anesthetized rats treated with saline (n = 9) or the specific elastase inhibitor methoxysuccinyl-L-Ala-L-Ala-L-Pro-L-Val-chloromethylketone (MAAPV, n = 6) underwent 4 h of bilateral hindlimb tourniquet ischemia followed by 4 h of reperfusion. At this time, in saline-treated rats, PMN were sequestered in lungs as assayed by myeloperoxidase activity [(MPO) 51 +/- 5 U/g tissue], higher than MPO in saline-treated sham rats (n = 9; 18 +/- 3 U/g MPO; P less than 0.01); bronchoalveolar lavage (BAL) fluid leukotriene (LT) B4 levels increased to 594 +/- 46 relative to 200 +/- 38 pg/ml in shams (P less than 0.01); increased permeability was documented by BAL fluid protein content of 599 +/- 91 compared with 214 +/- 35 micrograms/ml in sham animals (P less than 0.01); and edema was shown by increase in lung wet-to-dry weight ratio of 4.77 +/- 0.14 relative to 4.00 +/- 0.09 in sham rats (P less than 0.01). In MAAPV-treated animals, lung neutrophil sequestration (62 +/- 9 U/g MPO) and rise of LTB4 in BAL fluid (780 +/- 244 pg/ml) were not affected, but both BAL fluid protein (335 +/- 32 micrograms/ml) and lung wet-to-dry weight ratio (4.21 +/- 0.17) were reduced (both P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)