Extended focused assessment with sonography in trauma injury pattern associations in blunt versus penetrating trauma

Abstract

Background

Extended focused assessment with ultrasound for trauma (EFAST) is a key component in the assessment of trauma patients; however, there is a paucity of research regarding how injury patterns manifest in EFAST and how associations might differ in blunt versus penetrating trauma.

Methods

A retrospective review was conducted of EFAST studies at a level 1 trauma center, capturing 1356 EFAST exams. Chi-squared analysis was used to evaluate associations within trauma groups and to compare injury prevalence between trauma subgroups.

Results

Among all ultrasound exams, 34 (2.5%) had pneumothorax, 23 (1.6%) had pericardial fluid, and 63 (4.6%) had intra-abdominal fluid. In the blunt trauma subgroup, 29 (2.4%) had pneumothorax, 19 (1.6%) had pericardial fluid, and 50 (4.2%) had intra-abdominal fluid. In the penetrating trauma subgroup, 5 (4.9%) had pneumothorax, 1 (1%) had pericardial fluid, and 11 (10.8%) had intra-abdominal fluid. Pneumothorax was associated with intra-abdominal fluid across all scans (P = 0.03). Within the penetrating trauma subgroup specifically, intra-abdominal fluid was associated with pericardial fluid (P = 0.004), and intra-abdominal fluid was more likely to be present compared to the blunt trauma subgroup (P = 0.003). Pneumothorax and pericardial effusion incidence did not differ between trauma categories.

Conclusions

The strong association of pneumothorax with intra-abdominal fluid, and intra-abdominal fluid with pericardial fluid, underscores the critical role of a complete EFAST in trauma evaluation, particularly once evidence of injury in one of these anatomic regions is identified.

Extended focused assessment with ultrasound for trauma (EFAST) is a key component in the assessment of trauma patients, allowing for timely bedside diagnosis of life-threatening conditions such as hemoperitoneum, hemothorax, and pneumothorax. The standard views obtained are of the right upper quadrant, left upper quadrant, pericardium, suprapubic pelvis, and bilateral hemi-thoraces (anterior and lateral).^1,2 These studies are initially viewed by emergency providers to facilitate rapid diagnosis of these time-sensitive injuries.

Clinical decisions can be made efficiently with information obtained from EFAST exams, displaying high specificity and moderate sensitivity in the emergency department in cases of both blunt and penetrating trauma.^2–5 Accuracy of an EFAST exam is dependent on several factors that have been incompletely analyzed in the literature to date; these include provider level of training and experience, variation in patient habitus/body mass index, and technological and mechanical limitations.⁶ While point-of-care ultrasound is not a complete replacement for advanced imaging techniques like computed tomography, it does provide a quick, portable, and repeatable bedside option for the evaluation of patients, especially if they are not stable enough for more advanced studies.^7,8

In trauma situations, high utilization of resources and personnel is required to work up a patient and assess stability upon arrival.⁹ Varying degrees of injury can be present due to the wide range of mechanisms that can trigger a trauma activation, from gunshot wounds and crush injuries to motor vehicle collisions and geriatric falls.¹⁰ Because of the potential for critically ill patients in trauma cases, as well as high cost and resource consumption, it is important to understand the factors that may impact the accuracy of the EFAST exam to effectively treat and diagnose patients.¹¹

While studies have described the different injury patterns and resource utilization between blunt versus penetrating trauma, there is a paucity of research regarding how these patterns manifest in EFAST findings and how these associations might differ in blunt versus penetrating trauma. Limited research exists on injury pattern correlations in EFAST findings between blunt and penetrating trauma, particularly regarding combined injuries. We studied data from the trauma population at a large tertiary level 1 trauma center to help the emergency provider determine risk and therefore modify index of suspicion for associated injuries in the trauma patient as detected on EFAST.

METHODS

This retrospective study was approved by the institutional review board. All adult EFAST exams performed in the emergency department of a level 1 trauma center from June 6, 2022, to August 31, 2023, were included. Exams were performed by emergency medicine residents and attending physicians, with a quality assurance review conducted by ultrasound-trained staff to ensure accuracy and consistency.

Exams were analyzed for the presence of pneumothorax, pericardial fluid, and intra-abdominal fluid. Patients were categorized by trauma mechanism as blunt or penetrating, with four cases of preexisting ascites excluded due to confounding findings. Data on patient demographics and trauma mechanism were recorded when available.

Chi-squared analysis was performed to evaluate associations between injuries within trauma groups and to compare injury prevalence between blunt and penetrating trauma. A P value <0.05 was considered statistically significant. This approach was chosen because all outcomes were dichotomous (presence/absence of injury), allowing for straightforward assessment of independence and association between categorical variables. Subgroup analyses were performed to assess cross-compartment injury patterns separately in blunt and penetrating trauma populations.

RESULTS

A total of 1356 EFAST exams were captured in the archival system. Among all studies, 34 (2.5%) had a pneumothorax, 23 (1.6%) had pericardial fluid, and 63 (4.6%) had intra-abdominal free fluid. Four known cases of preexisting ascites were excluded. The mechanism of trauma was recorded in 1287 studies, of which 1185 (92%) were blunt and 102 (8%) were penetrating.

Among the blunt trauma subgroup, 29 (2.4%) had pneumothorax, 19 (1.6%) had pericardial fluid, and 50 (4.2%) had intra-abdominal free fluid. Pneumothorax was not associated with pericardial fluid, but it was associated with intra-abdominal fluid (P < 0.001). Intra-abdominal free fluid was not associated with pericardial fluid in the blunt trauma population.

Analyzing the penetrating trauma subgroup, 5 (4.9%) had pneumothorax, 1 (1%) had pericardial fluid, and 11 (10.8%) had intra-abdominal fluid. Pneumothorax was again not associated with pericardial fluid in this group, but it was associated with intra-abdominal free fluid (P = 0.03). Intra-abdominal free fluid was also associated with pericardial fluid in the penetrating trauma group (P = 0.004). When comparing blunt and penetrating trauma, there was no significant difference in the rate of pneumothorax. However, intra-abdominal fluid was more likely to be present in penetrating trauma (P = 0.003) (Figure 1).

Figure 1.

EFAST findings by trauma mechanism.

DISCUSSION

Based on a substantial body of prior literature on the use of EFAST in the emergency department, there is a clear benefit to its use as a tool in the expedited assessment of injuries in trauma patients.^2–7 However, associations between trauma mechanisms and their injury patterns have not been well described. In our study, we found that intra-abdominal free fluid was much more common in cases of penetrating trauma. This association is not surprising given the greater likelihood of significant organ and tissue laceration caused by penetrating trauma. Conversely, pneumothorax and pericardial effusion were observed at similar rates between trauma categories, suggesting that these injuries may be less dependent on the trauma mechanism and more reflective of overall trauma severity or forces directed at the thorax. The association between pneumothorax and intra-abdominal free fluid in the penetrating category can be understood by considering the frequency of thoracoabdominal penetrating injuries that cross the diaphragm and thus injure structures in both thoracic and abdominal compartments.¹² The same association seen in the blunt trauma population suggests that blunt traumatic energy strong enough to cause pneumothorax, usually accompanied by rib fractures, is also enough to lacerate abdominal viscera.

This study highlights a few significant differences in ultrasonographic injury patterns between blunt and penetrating trauma. While pneumothorax and pericardial effusion incidence did not differ between trauma categories, intra-abdominal fluid was significantly more common in penetrating trauma. The strong associations of pneumothorax with intra-abdominal free fluid and of intra-abdominal fluid with pericardial fluid underscore the critical role of a complete EFAST in trauma evaluation, particularly once evidence of injury in one of these anatomic compartments is identified. Emergency providers should maintain a high index of suspicion for intra-abdominal injuries, especially in cases of penetrating trauma where a thorough EFAST may assist in timely intervention.

Despite its strengths, including a large sample size, this study is not without limitations. Its retrospective design introduces the possibility of selection and reporting bias. For example, sicker patients may not have had their EFAST findings fully documented due to the urgency of their clinical condition. Additionally, the single-center nature of this study limits the generalizability of the findings. Lastly, the imaging was collected by providers of varying levels of training (PGY-1 through PGY-3 residents and attendings). This could produce variance in sensitivity based on skill and experience of the examiner. Future research could delve deeper into the correlation between specific injury patterns and patient outcomes, such as the impact of early identification and intervention on morbidity and mortality. Studies exploring the predictive value of EFAST findings for subsequent surgical or procedural interventions could also be valuable.

Our study provides valuable insights into the ultrasonographic injury patterns identified using EFAST in trauma patients, with a focus on differentiating between blunt and penetrating mechanisms of injury. The findings reinforce the critical role of EFAST as a rapid diagnostic tool, particularly in high-acuity trauma settings where timely decision-making can significantly impact patient outcomes.

DISCLOSURE STATEMENT

The authors report no funding or conflict of interest.