Background: Multiple organ failure after serious injury or illness is a major determinant of mortality. An initial insult is believed to "prime" circulating neutrophils and induce systemic inflammation. Thereafter, a second insult will precipitate distant organ injury. The aim of these studies was to evaluate circulating neutrophil function after mesenteric ischemia-reperfusion to determine the neutrophil "priming state," a quantitative and clinically useful predictor of multiple organ failure.
Materials and methods: Anesthetized Sprague-Dawley rats underwent superior mesenteric artery occlusion for 30 min or sham operation and were euthanized after 2, 6, or 24 h of reperfusion. Control animals had blood taken without any intervention. To determine changes in lung capillary permeability, another group of rats received Evan's blue, a dye that binds albumin, 1 h before sacrifice. Flow cytometric analysis was performed on 5 million white blood cells after removal of red cells by lysis and centrifugation. Neutrophil number, oxidative burst, and CD18 expression were measured.
Results: The number of circulating neutrophils was elevated similarly in rats subjected to sham operation or ischemia-reperfusion. Oxidative burst potential was increased at 2 h, maximum at 6 h, and normal at 24 h after reperfusion, but not in sham rats. CD18 expression was similar in all groups. There was a significant temporal correlation between the "priming state" of the circulating neutrophil, defined as the product of the neutrophil number times oxidative burst, and lung leak.
Conclusions: The neutrophil "priming state" may allow the clinician to better predict those patients at greatest risk for multiple organ failure.