Sonographic measurement of the inferior vena cava as a predictor of shock in trauma patients.

Detecting and monitoring blood loss is always a challenging dilemma in emergency settings. The diameter of the inferior vena cava (IVC) in trauma patients may be useful in this way. This has been classically done with computed tomography (CT); however, doing it with ultrasound as a bedside easily available modality is a relatively novel approach. Between January 2006 and March 2006, 88 injured patients referred to our center were investigated. The patients were divided in to two groups: a shock group (n = 11, 12.5%) and a control group (n = 77, 87.5%) who were trauma patients with normal blood pressure. The maximum anteroposteroir diameter of IVC was measured ultrasonographically both in inspiration (i) and expiration (e) by M-mode in the subxyphoid area. The difference between the diameters of IVCe and IVCi was regarded as collapsibility, and collapsibility index was defined as IVCe - IVCi/IVCe. Statistical analysis included Mann-Whitney U test and correlation analysis. The average diameters of IVCe and IVCi in the shock group at arrival were significantly smaller than in the control group (5.6 +/- 0.8 mm, 4.0 +/- 0.7 mm versus 11.9 +/- 2.2 mm, 9.6 +/- 2.0 mm; P < 0.0001). The maximum diameter of IVC in the shock group was in a 30-year-old male patient with an IVCe and IVCi of 7.0 and 5.3 mm, respectively. Correlation analysis revealed a negative correlation between the diameter of IVCe (r = 0.72) and IVCi (r = 0.73) and the presence of shock. Regarding the collapsibility index, the mean collapsibility index of IVC was significantly higher in the shock group compared to patients in the control group (27% versus 20%; P < 0.001). The diameter of IVC was found to correlate with shock in trauma patients. The measurement of the IVC may be an important addition to the ultrasonographic evaluation of trauma and other potentially volume-depleted patients and can be added to the focused assessment with sonography for trauma (FAST) of the trauma patient with minimum additional time.