Early neutrophil sequestration after injury: a pathogenic mechanism for multiple organ failure

Polymorphonuclear neutrophils (PMNs) play a pivotal role in the inflammation that precedes multiple organ failure (MOF). In a rat model of MOF, PMNs become primed for enhanced superoxide anion (O2-) release and CD11b expression, sequester in end organs, and produce organ failure. Therefore, we hypothesized that circulating PMNs harvested in the first 24 hours after injury from trauma patients at risk for MOF would (1) exhibit a primed O2- release, (2) upregulate CD11b expression, and (3) show evidence of sequestration in tissues. Extracellular PMN O2- release and CD11b receptor expression were measured at 3, 6, 12, and 24 hours after injury in 33 torso trauma patients with Injury Severity Scores > 15; eight patients (24%) developed MOF. Healthy adults served as controls. PMNs after injury were primed for enhanced in vitro O2- release at 3, 6, 12, and 24 hours after injury, indicating prior in vivo priming. CD11b expression was also increased at 6, 12, and 24 hours after injury. Circulating PMN numbers increased sharply at 3 hours after injury, before decreasing dramatically at 6 and 12 hours, suggesting end organ sequestration. At 12 hours after injury, declines in circulating PMNs were significantly greater in MOF than in non-MOF patients (p < 0.05). These data indicate that PMNs are quickly mobilized into the circulation after injury and then primed for enhanced O2- release and CD11b expression. PMN priming appears to be a necessary preamble to PMN sequestration in patients with major torso trauma. Upregulation of PMN function, accompanied by subsequent end organ sequestration, may represent an important early event in the pathogenesis of MOF after injury.