This is a retrospective, single-center, study conducted in a tertiary University Hospital. The study received approval by the Hospital’s Scientific Board. The radiological images of all patients undergoing MDCTA between January 2020 and June 2020 were analyzed. Inclusion criteria were: (a) three-phases MDCTA imaging available at PACS including unenhanced, arterial and parenchymal phase, (b) active bleeding identified during the arterial phase. Exclusion criteria were (a) cerebral or gastrointestinal bleeding and (b) only arterial or parenchymal phase available. In total, 30 patients fulfilled the above criteria and were included in the study. Their medical records were also analyzed, and clinical and laboratory findings were recorded. The following clinical parameters were obtained from the electronic Health Record System of our Institution: Hemoglobin and Hematocrit level before the MDCTA (same day), hemodynamic instability, in-hospital mortality, therapy plan (blood transfusion, embolization, and surgery), comorbidities, sepsis, and cause of death.
Our institution’s trauma/bleeding MDCTA protocol includes 3 phases: unenhanced, arterial and parenchymal phase. All cases in our study took place in a Philips 64 Brilliance CT scanner with slice thickness of 1,5mm, increment -0,75mm and pitch 0,5 in all 3 phases. The parenchymal phase usually takes place approximately 60 seconds after the region of interest (ROI) threshold during arterial phase has been reached. ROI was placed at the corresponding aorta level for suspicious bleeding, for example in case of abdominal hemorrhage ROI placed in the center of abdominal aorta lumen and in case of bleeding in thorax ROI was placed in thoracic aorta respectively. Two radiologists (AT, EE) with at least 5 years’ experience in Emergency-Trauma Radiology, calculated separately the extravasation rate of these bleeding cases by using Myrian® Analysis Software (Intrasense®, France). In each case the amount of active extravasation volume (ml) was calculated in arterial and parenchymal phases, by manually placing the mouse cursor and tracing active bleeding spots on each series. By clicking and coloring on each single slice the active bleeding area, the program was automatically measuring the corresponding bleeding volume, considering the slice thickness and summing up each slice’ s volume. If bleeding occurred in a discontinuity manner or in different locations within the body, all bleeding volumes were added together to determine the total active bleeding volume for each patient. After correlation of the two different radiologist’s results, mean arterial and parenchymal phase active bleeding volume was quantified. According to the bleeding volumetric results, bleeding rate was calculated for each case as follows: Using the bolus tracking technique at the arterial phase, the ROI was placed on the corresponding aorta level. Trigger for start of scanning was set at aortic enhancement of 150 HU. After the ROI threshold is reached, a “scan delay” occurs which is the time between bolus trigger and the helical scanning of the arterial phase. Scan delay lasts a few seconds and was detected respectively for each case. Bleeding rate was calculated based only on the active bleeding volume measured at the arterial phase using the following formula:
Grade of Bleeding Rate and Bleeding Volume
Bleeding rate and bleeding volume were graded using a 1 to 4 system (grade 1: very low, grade 2: low, grade 3 medium and grade 4: high. The cut-off value to classify a bleeding rate as grade 4 was ≥ 5ml/min which corresponds to the average volume of 1 Unit of transfused blood in one hour. The average volume of two bags of transfused blood corresponds to blood loss >15% of total circulating blood volume which is categorized as type II bleeding . Type II bleeding (15-30 % loss of total blood volume) is the time that the patient stops being asymptomatic and correlates with the first bleeding symptoms, such as nausea, fatigue, tachycardia and tachypnea. Therefore, a severe bleeding with high bleed rate was considered as a blood loss equal or higher to 1 blood Unit per hour. Respectively, grade 3 bleeding rate was set at ≥3 <5 ml/min, grade 2 at ≥1 <3 ml/min and grade 1 rate at <1 ml/min. The average time between trigger bolus and beginning of scanning in arterial phase (e.g. scan delay) was 10sec, hence corresponding bleeding volumes in arterial phase were calculated , approximated and categorized in severity scale as grade 1: <0.1 ml, grade 2: ≥0.1 <0.5 ml, grade 3: ≥0.5 <1 ml, and grade 4: ≥1 ml.
Study’s outcome measures
The study’s primary outcome measures were the quantification of active extravasation at the arterial and parenchymal phase of MDCTA using volumetry measurements as described above, the calculation of active bleeding rate and bleeding grading according to the volumetric analysis. The active bleeding rate was calculated by dividing the active bleeding volume by the time between bolus triggering and arterial phase.
Secondary endpoints were periprocedural (30-day) mortality rate, the identification of independent predictors of mortality and the identification of a correlation between volumetric analysis, various clinical features, and the decision to proceed with endovascular or surgical intervention.
Continuous variables were reported as mean ± standard deviation (SD). Categorical variables were reported as absolute frequencies /percentage. Normality was evaluated initially with the Kolmogorov-Smirnov goodness-of-fit test and independent sample t-test and Mann-Whitney U test were applied for parametric and non-parametric comparisons, respectively. The correlation between clinical variables (age, gender, Hb/Ht values, sepsis, hemodynamic instability, anticoagulation therapy, cause of bleeding), bleeding volume, bleeding grade, bleeding rate, mortality, and treatment plan, was evaluated. Specifically, the Pearson product-moment correlation coefficient was used to assess the association between normally distributed variables and the Spearman’s rank correlation coefficient was used to assess data that did not pass the normality test. A Cox multivariate regression analysis was performed for the identification of factors associated with endovascular or surgical intervention or in-hospital mortality. The variables analyzed in the multivariable model were pre-defined (based on medical relevance) and included: gender, cause of bleeding, grade of bleeding volume according to volumetric analysis at the arterial phase, grade of arterial bleeding rate, hemodynamic instability, and severe decrease of Hb (Hb <7 or <9 in patients with cardiac disease). Inter-observer variability was calculated for the volumetric analysis performed for the arterial and the parenchymal phases. Statistical analysis was performed with the IBM SPSS statistical software package (version 20.0; SPSS/PASW, Illinois, USA) and the level of statistical significance was set at p<0.05.