Background: Unwitnessed gastric aspiration can be a diagnostic dilemma, and early discrimination of different forms may help to identify individuals with increased risk of development of severe clinical acute lung injury or acute respiratory distress syndrome. The authors hypothesized that inflammatory mediator profiles could be used to help diagnose different types of gastric aspiration.
Methods: Diagnostic modeling using a newly modified receiver operator characteristic approach was applied to recently published data from our laboratory on lavaged inflammatory mediators from rodents given intratracheal normal saline, hydrochloric acid, small nonacidified gastric particles, or a combination of acid and small gastric particles. Multiple animal groups and postaspiration times of injury were analyzed to gauge the applicability of the predictive approach: rats (6 and 24 h), C57/BL6 wild-type mice (5 and 24 h), and transgenic mice on the same background deficient in the gene for monocyte chemoattractant protein 1 (MCP-1 [-/-] mice; 5 and 24 h).
Results: Overall, the four types of aspiration were correctly discriminated in 85 of 96 rats (89%), 72 of 78 wild-type mice (92%), and 59 of 73 MCP-1 (-/-) mice (81%) by models that used a maximum of only two mediators. The severe "two-hit" aspirate of the combination of acid and small gastric particles was correctly predicted in 21 of 24 rats, 23 of 23 wild-type mice, and 21 of 21 MCP-1 (-/-) mice. Specific best-fit mediators or mediator pairs varied with aspirate type, animal type, and time of injury. Cytokines and chemokines that best predicted the combination of acid and small gastric particles were cytokine-induced neutrophil chemoattractant 1 (6 h) and MCP-1 (24 h) in rats, tumor necrosis factor alpha/macrophage inflammatory protein 2 (5 h) and tumor necrosis factor alpha/MCP-1 (24 h) in wild-type mice, and tumor necrosis factor alpha/macrophage inflammatory protein 2 (5 h) and tumor necrosis factor alpha/keratinocyte-derived cytokine (24 h) in MCP-1 (-/-) mice.
Conclusions: These results support the potential feasibility of developing predictive models that use focused measurements of inflammatory mediators to help diagnose severe clinical forms of unwitnessed gastric aspiration, such as the combination of acid and small gastric particles, that may have a high risk of progression to acute lung injury/acute respiratory distress syndrome.