Year : 2019 | Volume
: 9 | Issue : 4 | Page : 193--196
Emergency focused assessment with sonography in blunt trauma abdomen
Shradha Engles1, Navdeep Singh Saini2, Shubra Rathore3,
1 Department of Vascular Surgery, Indraprastha Apollo Hospital, New Delhi, India
2 Departments of General Surgery, Christian Medical College, Ludhiana, Punjab, India
3 Departments of Radiodiagnosis, Christian Medical College, Ludhiana, Punjab, India
Navdeep Singh Saini
Department of Surgery, Christian Medical College and Hospital, Brown Road, Ludhiana - 141 008, Punjab
Background: Focused assessment with sonography in trauma (FAST) being a rapid noninvasive examination is used primarily to evaluate for the evidence of traumatic free fluid suggestive of injury in the peritoneal, pericardial, and pleural cavities. It is widely recognized as a mainstream emergency skill in the management of trauma. Aim: The aim of the study is to evaluate the accuracy of FAST in patients presenting with blunt abdominal trauma. Methods: Data were collected prospectively from FAST scans conducted in blunt trauma abdomen (BTA) patients. Positive and negative FAST scans were confirmed either with contrast-enhanced computed tomography (CECT) abdomen or with exploratory laparotomy, thus dividing it further into four groups, i.e., true-positive, false-positive, true-negative, and false-negative scans. After collecting the data, accuracy of FAST was calculated. Results: In this study, a total of 104 patients were included. The mean age was 38.17 years. Most common cause of BTA was road traffic accident. The overall sensitivity, specificity, and accuracy of FAST were 69.8%, 92.1%, and 80.8%, respectively. Conclusion: This study showed that FAST is of paramount importance in patients who are hemodynamically unstable as it has a high positive predictive value. However, a FAST-negative result should always be confirmed by other modalities.
|How to cite this article:|
Engles S, Saini NS, Rathore S. Emergency focused assessment with sonography in blunt trauma abdomen.Int J App Basic Med Res 2019;9:193-196
|How to cite this URL:|
Engles S, Saini NS, Rathore S. Emergency focused assessment with sonography in blunt trauma abdomen. Int J App Basic Med Res [serial online] 2019 [cited 2020 Jan 23 ];9:193-196
Available from: http://www.ijabmr.org/text.asp?2019/9/4/193/268937
Abdominal injuries have been reported as the leading cause of preventable deaths in trauma victims. Thus, the objective evaluation of the abdomen by imaging methods becomes necessary in such patients. In 1996, Rozycki et al. coined the term focused assessment with sonography in trauma (FAST) that stands for FAST. According to the ATLS protocol, FAST should be performed immediately after the primary survey. It is a very useful tool in hemodynamically unstable patients. Studies have shown that FAST decreases time for appropriate intervention by 64%–76%, reduces the requirement for computed tomography (CT) scanning, and decreases complication rates and length of hospital stay. It can be done in 5 min and consists of 4–6 views (3–5 intra-abdominal and 1 cardiac), with the intent being the identification of free fluid within the abdomen. The specificity of FAST has been reported to be in the range from 98% to 100%. Various studies done have shown the accuracy of FAST to be in the range from 98% to 99%. What has made it so popular is the fact that it decreases the time needed for diagnosis and it can be executed at the bedside. It is noninvasive, and it does not require a contrast medium or radiation. It is safe in pregnant woman and in children and can be performed serially. It has high specificity to detect free fluid, between 98% and 100%. It can be used to diagnose and assess the degree of hemoperitoneum. Despite all these advantages, it has its own pitfalls which include a lower sensitivity to detect peritoneal fluid, between 73% and 88%, inability to detect retroperitoneal fluid, a limited ability to detect organ lesions, being operator dependent, and difficult in obese individuals. For these reasons, abdominal CT is considered the radiological gold standard. Although considered the gold standard, drawbacks of CT include possible artifacts due to the patient's movement, possible renal toxicity, radiation exposure, and cost.
It was an observational prospective study, including all patients with age ≥18 years with a history of blunt trauma abdomen (BTA) presenting to the Emergency Department during the time period of November 1, 2015–October 31, 2016. Patients with overt/obvious signs of peritonitis were excluded.
Data were collected prospectively from FAST scans conducted in BTA patients during the study period. FAST was performed by a General Electric Logic 200 device using a 3.5 MHz (Megahertz) abdominal probe by a radiologist.
Positive and negative FAST scans after being confirmed with either CECT abdomen and/or based on operative findings were further divided into four groups: true positive scans in which intra-abdominal free fluid was present on FAST and also present on either CECT abdomen or exploratory laparotomy (EL), false-positive scans with positive FAST result but absent free fluid on either CECT abdomen or EL, true-negative scans with absent intra-abdominal free fluid on FAST and also absent on either CECT abdomen or EL, and false-negative scans with negative FAST but with free fluid present on either CECT abdomen or EL.
All cases satisfying the inclusion criteria were studied. Data was entered into Microsoft Excel and analyzed. True-positive, true-negative, false-negative, and false-positive values were calculated. Sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV), and accuracy of FAST were calculated.
In this study, a total of 104 patients were enrolled. FAST was done in all BTA patients within half and hour of presentation. The FAST results were compared with the results of CECT abdomen or EL or both.
About 89.42% (n = 93) patients were male and 10.58% (n = 11) were female. The mean age was 38.17 years.
Only 8 patients (7.7%) presented within 1 h of sustaining the trauma. Almost 77% BTA cases were due to road traffic accidents (RTAs), 12.5% by fall from height, 3.8% each by assault and industrial accidents, and rest from railway accidents (1.9%) or animal attack (0.96%).
About 46.2% of the patients were hypotensive with a blood pressure of ≤100/60 mmHg and 53.8% of the patients were normotensive with a blood pressure of ≥100/60 mmHg at the time of presentation.
About 58.6% of the patients had associated injuries in the form of long bone fractures, rib fractures, soft-tissue injuries, and head and spine injures had isolated BTA with no associated injuries. 39.4% of the patients showed FAST-positive results and 60.6% of the patients showed FAST-negative results.
85.6% of FAST scans were followed by CECT abdomen to confirm the findings, 7.7% underwent only emergency EL, 5.8% of the patients underwent both CECT Abdomen and emergency EL, and 0.96% of the patients underwent wound exploration.
On comparison of FAST results with CECT/laparotomy findings, 35.6% of the FAST results were true-positive, 45.2% were true-negative, 15.8% were false-negative, and 3.8% were false-positive results.
In hypotensive patients, 43.7% had FAST positive and 56.3% patients had FAST negative. In this group, 37.5% of FAST scans were found to be true positive, 35.4% true negative, 6.3% were false positive, and 20.8% came as false negative. In normotensive patient group, FAST was positive in 35.7% of the patients and negative in 64.3% of the patients. 32.1% of the scans in this group were true positive, 51.8% were true negative, 3.6% of patients were false positive, and 12.5% of the patients were false negative.
The overall sensitivity of FAST in this study was 69.8% and overall specificity was 92.1%. Overall PPV, NPV, and accuracy of FAST were 90.2%, 74.6%, and 80.8%, respectively.
The sensitivity of FAST in hypotensive patients was 64.2%. Specificity in this group was 85%. PPV, NPV, and accuracy was 85.7%, 62.9%, and 72.9%, respectively.
The sensitivity, specificity, PPV, NPV, and accuracy of FAST in normotensive group of patients were 72.0%, 93.5%, 90%, 80.5%, and 83.9%, respectively.
In this study, the mean age was 38.17 years. Majority of cases (89.42%) belonged to male gender. In a study done by Fleming et al., a total of 100 patients were included out of which 62% of the patients were male and the mean age of participants was 41 years which is comparable to our study. In another study done by Farahmand et al., 60% of the patients were males and the mean age of participants was 45 years. This higher number could be attributable to more number of males driving vehicles on the road or being the major part of workforce, making them more prone to injuries as compared to the female gender in both the situations.
Only 7.7% patients could reach the emergency department within 1 h of BTA called the golden period of trauma. Intervention done within this period decreases the mortality and morbidity among trauma patients significantly. This delay in time of presentation post-BTA can be one of the reasons of hemodynamic instability at the time of presentation. It can be due to delay in transport or in arrival of an ambulance at the site of trauma and signifies the need to revamp the prehospital care and transport of sick patients to the nearest hospital in the state.
76.9% patients patients had sustained blunt trauma in a RTA (vehicle to vehicle or vehicle to pedestrian). 12.5% had a history of fall from height, 3.8% patients had BTA after assault, and another 3.8% from industrial accidents. In a study done by Kornezos et al., 78% of the total cases were motor vehicle accidents, 17% sustained falls from a height, and 5% assault or other causes, which is comparable to our study. In another study done by Smith and Wood, 74.1% had sustained blunt traumatic injury post-RTA which is comparable to our study.
The study reported 48 (46.2%) patients as hypotensive and 56 (53.8%) as normotensive at the time of presentation to emergency which is comparable to the study done by Kumar et al. in which 56% of the patients were unstable at the time of presentation. This high number (46.2%) again highlights the need to strengthen our prehospital care and revamping the healthcare facilities required for same.
All the patients who underwent emergency EL only on the basis of FAST-positive result, showed significant free fluid in the abdomen in form of hemoperitoneum and solid organ injury (true positive). In this study, high false-negative results were noted. One of the main reasons for this can be performing FAST after urinary catheterization. In a study done by McGahan et al. on comparing FAST with CT, 14 false-negative FAST results were noted. 6 of these were due to the identification of free fluid in the pelvis at CT but not on FAST, owing to lack of a full bladder. Thus, emphasizing the need to develop a method or technique to keep the urinary bladder full during the FAST scan to displace bowel gas and decrease the likelihood of missing a pelvic hemoperitoneum.
The sensitivity of FAST in this study (69.8%) is comparable to the study done by Remedios et al., where a sensitivity of 67% was noted. However, their study showed a higher specificity of 99% as compared to our study (92.1%). In another study done by Natarajan et al., the overall FAST results showed a specificity of 99% and PPV of 95% and NPV of 94%, respectively; however, the sensitivity in their study was found to be only 43% which was less than that found in the literature. In the study done by Fleming et al., FAST had a specificity of 94.7%, sensitivity of 46.2%, PPV of 0.96, and NPV of 0.39. In another study done by Kumar et al., the overall sensitivity, specificity, and accuracy of FAST were 80.4%, 75%, and 80%, respectively, for the detection of free fluid in the abdomen. In the study done by McGahan and Richards, the sensitivity, specificity, and accuracy was 60%, 98%, and 80%, respectively, for free intraperitoneal fluid on FAST which is comparable to this study.
The sensitivity of FAST in hypotensive patients in this study was 64.2%. The specificity, PPV, and NPV were 85%, 85.7%, and 62.9%, respectively. The accuracy of ultrasound FAST in hypotensive group was 72.9%. In a study done by Lee et al., over a period of 6 years on 4029 patients, 122 of the patients were hypotensive on admission. The result showed 85% sensitivity, 60% specificity, and 77% accuracy in the hypotensive group which is comparable to our study.
The sensitivity of FAST in normotensive group of patients in our study was 72% and the specificity was 93.5%. The PPV and NPV was 90% and 80.5%, respectively. The accuracy of ultrasound FAST in normotensive group was 83.9%. In a study done by Lee et al., in the normotensive group of patients, the sensitivity was reported to be 85%, the specificity 96%, and the accuracy 96%.
When the results were compared between the hypotensive and normotensive group of patients, we observed that the sensitivity, specificity, the PPV, the NPV, and accuracy were higher in the normotensive group of patients. Overall, the PPV and specificity were high even though the sensitivity and accuracy to detect free fluid in the peritoneal cavity was low. The overall sensitivity and specificity of FAST in our study was 69.8% and 92.1%, respectively, which is comparable to the available literature.
A Cochrane systematic review found that the sensitivity for detecting hemoperitoneum in trauma patients was 85%–95%. The randomized control trial showed low sensitivity of ultrasound. But despite the proven lack of sensitivity, the results of this review suggested minor efficiency of ultrasonography in the trauma setting. Because of its high specificity, a positive sonogram (either for free fluid or organ injury) proves the presence of intra-abdominal damage, but given its poor overall sensitivity, ultrasound cannot be used alone to rule out abdominal injury.
Despite all cautions taken while conducting the study, the study may be limited by its small sample size, subjective-/operator-dependant reporting of FAST, body built of the patients, and catheterization of patients before performing FAST, thus decreasing the possibility of finding free fluid in the pelvis.
In this study, the accuracy of FAST was low for both hypotensive as well as normotensive group of patients, but the PPV was high in both the groups. Thus, even though FAST has its own limitations, all FAST-positive examinations are valuable, especially in all hemodynamically unstable patients. Hypotensive patients, who are FAST positive, can be immediately taken to the operating room, thereby decreasing the mortality and morbidity in these patients. For negative FAST result, further investigation such as computed tomography is recommended, as FAST-negative result does not rule out solid organ, mesenteric, or a retroperitoneal injury. In conclusion, FAST is an effective, initial, diagnostic, and screening tool to triage unstable patients with BTA.
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