Initial inferior vena cava diameter on computed tomographic scan independently predicts mortality in severely injured trauma patients.

BACKGROUND: In the trauma population, patients with physiologic compromise may present with "normal" vital signs. We hypothesized that the inferior vena cava (IVC) diameter could be used as a surrogate marker for hypovolemic shock and predict mortality in severely injured trauma patients.

METHODS: A retrospective cohort study was performed at a Level I trauma center on 161 severely injured adult (aged ≥ 16 years) trauma patients who were transported from the scene and underwent abdominal computed tomography within 1 hour. Exposure of interest was dichotomously defined as having an infrarenal transverse to anteroposterior IVC ratio of ≥ 1.9 (flat IVC) or <1.9 (not exposed) based on the area under the curve analysis. The primary outcome was in-hospital mortality. Covariates included initial heart rate, systolic blood pressure, bicarbonate, base excess, creatinine, hemoglobin, and Injury Severity Score (ISS). Correlation analysis between IVC ratio and other known markers of hypoperfusion was performed. Logistic regression was used to determine the independent effect of the IVC ratio on mortality.

RESULTS: Of the 161 patients, 30 had a flat IVC. The IVC ratio had a significant (p < 0.05) inverse correlation with initial bicarbonate, hemoglobin, and base excess and a direct correlation with Cr and ISS. After controlling for age, ISS, and presence of severe head injury, patients who had a flat IVC were 8.1 times (95% confidence interval, 1.5-42.9) more likely to die compared with the nonexposed cohort. Importantly, heart rate and systolic blood pressure had no predictive value in this patient population.

CONCLUSION: A flat IVC on initial abdominal computed tomographic scan has a significant correlation with other known markers of shock and is an independent predictor of mortality in severely injured trauma patients. This finding should heighten the awareness of the need for aggressive intervention and potential for physiological decompensation in patients with otherwise "normal" vital signs.

LEVEL OF EVIDENCE: Prognostic study, level III.