Clinical utility of flat inferior vena cava by axial tomography in severely injured elderly patients.

BACKGROUND: Flat inferior vena cava (IVC) has been associated with shock and mortality in young trauma patients (age < 55 years). Because of the greater possibility of nonhypovolemic shock in the elderly, we hypothesized that there would be no correlation between IVC ratio and the presence of shock.

METHODS: We conducted a retrospective cohort study of all severely injured (Injury Severity Score [ISS] ≥ 15), blunt trauma patients 55 years or older from April 2006 to April 2011. Only patients undergoing axial imaging of the IVC within 1 hour of arrival were considered. Anteroposterior and transverse diameter of the IVC were measured 2.5 mm above the renal veins. Transverse-to-anteroposterior IVC ratios of 2, 3, and 4 were analyzed. Hemodynamic (heart rate, blood pressure, systolic blood pressure, shock index, and adjusted shock index [ASI]) and laboratory (hemoglobin, HCO, base excess) markers of shock were reviewed. Correlation among shock markers, IVC ratio, and death was analyzed using multivariate logistic regression. Relationship between shock and IVC ratio was analyzed using logistic regression and χ where appropriate.

RESULTS: A total of 308 patients met the inclusion criteria during the study period. The IVC ratio was greater than 2, greater than 3, and greater than 4 in 180, 85, and 46 patients, respectively. The IVC ratio (analyzed continuously) correlated with mortality (p < 0.05). Ratios of greater than 3 and greater than 4 predicted a 2.0 and 2.2 times mortality increase (95% confidence interval, 1.00-5.00 and 1.00-4.95, respectively). IVC ratio did not correlate with shock (ASI > 50) for any of the ratios studied.

CONCLUSION: As in previous studies with younger injured patients, a flat IVC is predictive of increased mortality risk in the elderly. Presence of a shock state, as defined by ASI, is not correlated with a flat IVC. Moreover, almost one third of patients presenting in shock had a round IVC. This is consistent with our hypothesis that shock in the elderly trauma population may be multifactorial and the risk of nonhypovolemic shock must be considered.

LEVEL OF EVIDENCE: Diagnostic study, level IV.