Validation of the American Association for the Surgery of Trauma grading system for acute mesenteric ischemia - More than anatomic severity is needed to determine risk of mortality

BACKGROUND Acute mesenteric ischemia (AMI) is a highly morbid disease with a diverse etiology. The American Association for the Surgery of Trauma (AAST) proposed disease-specific grading scales intended to quantify severity based upon clinical, imaging, operative, and pathology findings. This grading scale has not been yet been validated for AMI. The goal of this study was to evaluate the correlation between the grading scale and complication severity. METHODS Patients for this single center retrospective chart review were identified using diagnosis codes for AMI (ICD10-K55.0, ICD9-557.0). Inpatients >17 years old from the years 2008 to 2015 were included. The AAST grades (1-5) were assigned after review of clinical, imaging (computed tomography), operative and pathology findings. Two raters applied the scales independently after dialog with consensus on a learning set of cases. Mortality and Clavien-Dindo complication severity were recorded. RESULTS A total of 221 patients were analyzed. Overall grade was only weakly correlated with Clavien-Dindo complication severity (rho = 0.27) and mortality (rho = 0.21). Computed tomography, pathology, and clinical grades did not correlate with mortality or outcome severity. There was poor interrater agreement between overall grade. A mortality prediction model of operative grade, use of vasopressors, preoperative serum creatinine and lactate levels showed excellent discrimination (c-index = 0.93). CONCLUSION In contrast to early application of other AAST disease severity scales, the AMI grading scale as published is not well correlated with outcome severity. The AAST operative grade, in conjunction with vasopressor use, creatinine, and lactate were strong predictors of mortality. LEVEL OF EVIDENCE Prognostic study, III.