| Background and Objective:Trauma is becoming the first public hazard of modern society globally. According to the statistics, over 500 million people died from trauma annually, accounting for 9% of the total number of deaths globally. There are 9.5 people die from accidental trauma per minute on average. In our country, the annual traumatic death number is over 70 million. It is the fifth cause of death now. The treatment of trauma, especially severe trauma has becoming an important problem for the modern medicine. In severe trauma patients, the condition of injuries are often complex and critical. The quick and accurate assessment of the injury is the key in the treatment of severe trauma patients.The computed tomography (CT) scanning has become an essential tool for the early stage of trauma care because of its high diagnostic accuracy. Moreover, the introduction of multi-slice spiral computed tomography (MSCT) scanners and infrastructural improvements makes the total-body CT scanning technically feasible, which is widely used in severe trauma patients. However, during the transfer of patients to the radiology department or after the examination, sudden deterioration of hemodynamic status may occur.Hypoperfusion of tissue and organ is the key role in shock. When trauma patients is lack of circulating blood volume due to blood loss, our body will activate the sympathetic nervous system and the renin-angiotensin system to sacrifice the blood supply of the gastrointestinal tract, kidney, skin and other organs to guarantee life organ's. Abdominal organs are the first part to sacrifice the blood supply in the early stages of shock. Reduction of the blood supply of the abdominal organs presents with hypoperfusion status in the enhanced CT imaging. As total circulating volume decreased continuously, blood returning to the IVC reduced and was unable to maintain tension of the vessel wall. Under the oppression of the abdominal organs, the vessels deformed and collapsed, there will be signs of the collapse of the great vessels of the aorta, inferior vena cava. Based on the understanding of the pathophysiology of shock and CT signs of hypovolemic shock patients observed, apply MSCT in the assessment of hemodynamic status in severe trauma patients will be a completely new idea. The widely use of MSCT in the early treatment of patients with severe trauma can not only shorten the time from admission to give definitive treatment effectively, but also provide us a more comprehensive understanding of the perfusion of organs and indicate the endpoint of resuscitation.Accordingly, this study hoped to analyze the CT information in patients with severe trauma by quantifying the CT data of abdominal vessels and parenchymal organs. According to the occurrence of shock event after admission, the trauma patients were divided into stable group and shock group. The differences of the CT data between the two groups were compared to explore the CT imaging findings that may be used to assess hemodynamic status trauma patients, providing the data support to its further appliance.Methods:The clinical and MSCT data of 63 severe trauma patients admitted to our trauma center from January 2008 to December 2011 were reviewed. The patients were divided into stable group and shock group according to the occurrence of hypovolemic shock within 24 hours after CT scan. Calibres of abdominal vessels and the mean CT value of abdominal organs both in early and delayed phase were measured. Differences of indexes between the two groups were compared using statistical methods. Receiver operating characteristic curve(ROC) analysis was performed to assess the predictive accuracy of these signs for hypovolemic shock. Finally, a joint CT diagnosis model was established by logistic regression. A new CT diagnosis index, CTSI (CT Shock Index) was created. After substituting the patient data into the new index equation, ROC analysis was used to evaluate the diagnostic performance of the final prediction model.Results:1. The difference between shock group (n=34) and stable group (n=29) in gender, age, time from injury to admission, time from injury to CT scan, the average length of stay and the average ICU days, was not statistically significant (P> 0.05). Mortality in the shock group was significantly higher than the stable group (P< 0.001), and the average amount of blood transfusion in shock group was significantly greater than the stable group (5986 ± 6510ml vs. 1083 ± 2068ml,P< 0.001); In the shock group, HR, SBP, Hgb and Hct was not significantly different from the stable group(P> 0.05); But the ISS and SI was significantly greater than the stable group (30 ± 8 vs 22 ± 6, P< 0.001; 1.17 ± 0.37 vs 0.96 ± 0.33, P= 0.019). In Blood gas analysis indexes, no significant difference was found in blood pH between the two groups (7.37 ± 0.05 vs 7.35 ± 0.05, P= 0.019), but Lac was significantly higher and BE was lower than the stable group (3.27 ± 0.69 mmol/L vs 2.56 ± 0.89 mmol/L, P= 0.021;-3.67 ± 2.66 mmol/L vs 1.34± 2.72 mmol/L, P< 0.001).2. The IVC showed collapsed trend in shock group and the flatness index of IVC(T/AP) were significantly greater than the stable group on four predetermined levels (P< 0.05). The maxium T/AP was on IVC2 (4.08 ± 1.79), and minimum in the IVC4 (2.18 ± 0.93); Diameter of the abdominal aorta,superior mesenteric artery and superior mesenteric vein in the predetermined level showed no significant difference compared to the stable group (P> 0.05);3. In the early phase of CT scan, CT values of superior mesenteric artery shock group was significantly lower than the stable group (133.2 ± 32.4HU vs 186.3 ± 23.3HU, P= 0.021), but no significant difference was found in the abdominal aorta and the superior mesenteric vein (P> 0.05). The CT value of IVC in shock group was significantly higher than the stable group only in IVC1(133.4 ± 20.3HU vs 112.0 ± 21.9HU, P= 0.018). In delayed phase, the difference was not statistically significant between the two groups (P> 0.05).4. In the early phase of CT scan, CT value of spleen in shock group was significantly lower than the stable group (), and the adrenal was higher (93 ± 16HU vs 112 ± 24HU P= 0.001; 153 ± 35HU vs 131 ± 24HU, P= 0.007); But the liver, pancreas, kidney cortex and medulla was not statistically significant (P>0.05). In the delayed phase, only the CT values of renal medullary in shock group was significantly lower than the stable group (193 ± 57HU vs 228 ± 53HU, P= 0.014), and no significant difference waa found in other organs(P> 0.05);5. ROC curve analysis showed that the optimal cutoff points of traditional injury assessment indexes for shock(shock index, ISS, blood lactate and base excess) were 1.19,19.5, 2.75 mmol/L and -2.88 mmol/L separately. The BE had the largest AUC(0.866), SEN and SPE were 88.2% and 80.3% at the optimal cutoff point. The shock index had the smallest AUC(0.688) and SPE and SPE were only 55.9% nd 86.2% respectively.In CT indexes, the optimal cutoff point of the flatness index of IVC(T/AP) CT values of SMA, IVC, spleen, adrenal glands in early phase and renal medulla in delayed phase were the 3.02,166 HU, 121HU,115HU,150HU,184HU respectively. T/AP had the largest AUC of 0.833. The SEN and SPE were 73.5% and 86.2% at the optimal cutoff point respectively. Mean CT values of the renal medulla had the smallest AUC(0.677), and the SEN and SPE were 47.1% and 82.8% respectively at the optimal cutoff point.6. CTSI was derived from integration of six CT indexes. CTSI= X1-0.040X2 +0.254X3-0.331X4+0.455 X5-0.196X6 (X1= T/AP, X2= CT value of SMA in early phase, X3= CT value of IV C in early phase, X4=CT value of spleen in early phase, X5= CT value of adrenal glands in early phase, X6= CT values of renal medulla in delayed phase). Though ROC analysis, CTSI had an AUC of 0.9038, and the SEN and SPE were 92.1% and 90.3% separately at the optimal cutoff point 21.23 with overall prediction accuracy of 91.7%.Conclusions:1. Patients in shock group showed no significant differences in HR, SBP, Hgb and Hct compared with stable group on admission, but had higher ISS, SI, Lac and lower BE than stable group;2. By quantitative analysis of the CT imaging data between stable group and shock group patients, it is found that collapsed IVC, early enhanced IVC, hypoperfusion of the SMA and spleen, excessive enhanced adrenal glands and weakened enhancement in delay phase have potential value in predicting the occurence of hypovolemic shock in severe trauma patients;3. Integrate CT indexes scientifically and rationally by using mathematical and statistical methods to innovatively create CT shock index (CTSI), a new concept shock prediction. The sensitivity and specificity of CTSI were 92.1% and 90.3% respectively at the optimal cutoff point 21.235. And this new index may have potential clinical application value;4. This study demonstrated that MSCT can be used to predict hypovolemic shock in severe trauma patients. The findings and result of this study can provide data support to the further large scale prospective clinical trial. |
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