Neutrophil priming state predicts capillary leak after gut ischemia in rats

Background. Multiple organ failure after serious injury or illness is a maj or determinant of mortality. An initial insult is believed to "prime" circu lating neutrophils and induce systemic inflammation. Thereafter, a second i nsult will precipitate distant organ injury. The aim of these studies was t o evaluate circulating neutrophil function after mesenteric ischemia-reperf usion to determine the neutrophil "priming state," a quantitative and clini cally 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 euthanize d after 2, 6, or 24 h of reperfusion. Control animals had blood taken witho ut any intervention. To determine changes in lung capillary permeability, a nother group of rats received Evan's blue, a dye that binds albumin, 1 h be fore sacrifice. Flow cytometric analysis was performed on 5 million white b lood cells after removal of red cells by lysis and centrifugation. Neutroph il number, oxidative burst, and CD18 expression were measured. Results. The number of circulating neutrophils was elevated similarly in ra ts subjected to sham operation or ischemia-reperfusion. Oxidative burst pot ential was increased at 2 h, maximum at 6 h, and normal at 24 h after reper fusion, but not in sham rats. CD18 expression was similar in all groups. Th ere was a significant temporal correlation between the "priming state" of t he 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 bett er predict those patients at greatest risk for multiple organ failure.