FAST scan: Is it worth doing in hemodynamically stable blunt trauma patients?

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1 FAST scan: Is it worth doing in hemodynamically stable blunt trauma patients? Bala Natarajan, MBBS, Prateek K. Gupta, MD, Samuel Cemaj, MD, Megan Sorensen, RN, BSN, Georgios I. Hatzoudis, MD, and Robert Armour Forse, MD, PhD, Omaha, NE Background. During the last decade, focused assessment with sonography for trauma increasingly has become the initial diagnostic modality of choice in trauma patients. It is still questionable, however, whether its use results in the underdiagnosis of intra-abdominal injury. It also remains doubtful whether a positive focused assessment with sonography for trauma affects clinical decision making in hemodynamically stable blunt trauma patients as evidenced through abdominal computerized tomography use. The aim of this study was to evaluate the results of focused assessment with sonography for trauma in hemodynamically stable blunt trauma patients and to determine its role in the diagnostic evaluation of these patients. Methods. We reviewed our prospectively maintained trauma database. In trauma patients at our institute, focused assessment with sonography for trauma examinations are performed by surgery residents and are considered positive when free intra-abdominal fluid is visualized. Abdominal computerized tomography, diagnostic peritoneal lavage, or exploratory laparotomy findings were used as confirmation of intra-abdominal injury. Results. In our 7-year study period, 2,980 trauma patients were evaluated at our institute, of which 2,130 patients underwent a focused assessment with sonography for trauma. In all, 18 patients had an inconclusive focused assessment with sonography for trauma, whereas 7 patients died on arrival, leaving 2,105 patients for our analysis. A total 88 true positive focused assessment with sonography for trauma were conducted. All hemodynamically stable blunt trauma patients who had a positive focused assessment with sonography for trauma (70/88) were confirmed by computerized tomography. Patients who underwent exploratory laparotomy directly (17/88) or diagnostic peritoneal lavage (1/88) as confirmation either had penetrating trauma or became hemodynamically unstable. A total of 1,894 true negative focused assessments with sonography for trauma scans were conducted, with 1,201 confirmed by computerized tomography and the rest by observation. In all, 118 false negative focused assessment with sonography for trauma were performed, of which 44 (37.3%) subsequently required exploratory laparotomy. Five patients had false positive focused assessment with sonography for trauma scans. Focused assessment with sonography for trauma scan had an overall sensitivity of 43%, a specificity of 99%, and positive and negative predictive values of 95% and 94%, respectively. Accuracy was 94.1%. In the hemodynamically stable blunt trauma group, there were 60 patients with true positive focused assessment with sonography for trauma examinations and 87 patients with false negative focused assessment with sonography for trauma examinations. In this group of patients, focused assessment with sonography for trauma had a sensitivity of 41%, specificity of 99%, and positive and negative predictive values of 94% and 95%, respectively. The overall accuracy was 95%. Conclusion. Given the low sensitivity, a negative focused assessment with sonography for trauma without confirmation by computerized tomography may result in missed intra-abdominal injuries. It is also observed in all focused assessment with sonography for trauma positive hemodynamically stable blunt trauma patients, confirmation is preferred through the use of a computerized tomography for better understanding of the intraabdominal injuries and to decide on operative versus no-operative management. Thus, the use of focused assessment with sonography for trauma in hemodynamically stable blunt trauma patients seems not worthwhile. It should be reserved for hemodynamically unstable patients with blunt trauma. ( 2010;148: ) From the Department of, Creighton University, Omaha, NE Accepted for publication July 15, Reprint requests: Robert Armour Forse, MD, PhD, Department of, Creighton University, 601 North 30th Street, Omaha, NE armour.forse@creighton.edu /$ - see front matter Ó 2010 Mosby, Inc. All rights reserved. doi: /j.surg THE USE OF ABDOMINAL ULTRASONOGRAPHY FOR TRAUMA VICTIMS IN THE EMERGENCY ROOM (ER) has become an accepted part of evaluation protocols in many hospitals in the United States. Blunt abdominal trauma continues to present several diagnostic challenges. In patients who are hypotensive, ultrasound is fast and can be done at the bedside; several SURGERY 695

2 696 Natarajan et al October 2010 observational studies have shown its utility as a screening test in this setting. 1-5 In the stable patients for whom time is not a constraint in management, the position of ultrasonography in the diagnostic algorithm has not been well established. Ultrasonography compares unfavorably with computerized tomography (CT) to detect injuries. Missed injuries are a major concern in this setting. The aim of this study was to evaluate the results of the focused assessment with sonography for trauma (FAST) examination in the hemodynamically stable blunt trauma patients and to determine its role in the diagnostic evaluation of these patients. MATERIALS AND METHODS All trauma patients who were admitted to our institute between January 2002 and December 2008 and entered into our trauma database were reviewed. Our center is a state designated level 1 trauma center and is one of the 2 major trauma centers serving the state of Nebraska. Patients are entered prospectively into the trauma database by the trauma service. The registry contains information about all documented injuries and is updated if new or delayed injuries are found. The data analyzed from the trauma database included race, sex, mode of injury (blunt/penetrating), blood pressure in ER, FAST, and CT findings, injuries sustained, surgeries performed, hospital duration of stay, and disposition. The initial evaluation of the trauma patient at our center in the ER is performed with a primary and secondary survey, which includes physical examination, chest and pelvic radiography, and the FAST examination. The FAST examination is performed by a surgery resident under the supervision of an attending trauma surgeon. The trauma surgeons were credentialed on their FAST skills by the Trauma Director. The trauma director was trained in the FAST examination and was certified by radiologists specializing in ultrasonography. During the FAST, 4 windows are studied--- pericardial, perihepatic, perisplenic, and pelvic. In cases where visualization of the pericardial window is difficult from subxiphoid position, the ultrasound probe is placed in the left second intercostal space in the midclavicular line. The FAST examination is interpreted as positive, negative, or indeterminate. The FAST examination is considered positive when free intra-abdominal or pericardial fluid is visualized, and it is negative in the absence of this. Indeterminate FAST studies include those where visualization of the organs is inadequate or when there is doubt about the result of the study. All FAST studies are performed and the results are recorded in real time by both the trauma nurse and the surgeon separately. The FAST examination is repeated in the emergency department only if there is any doubt based on the clinical picture. This is not by protocol. The z.one Convertible Ultrasound system (version 2.0; Zonare Inc., Mountain View, CA) with a 2--5-MHz convex array transducer was used to perform all ultrasonographies. Radiologists do not confirm the results of FAST examination. The definitions of results are as follows: True positive: FAST positive and the injury is confirmed by the best available reference. True negative: FAST negative and the lack of injury is confirmed by the best available reference. False positive: FAST positive and the lack of injury is confirmed by the best available reference. False negative: FAST negative and the injury is confirmed by the best available reference. Accuracy: The sum of the true FAST results divided by the total number of patients included for analysis. Confirmatory test: Abdominal/pelvic CTscan, diagnostic peritoneal lavage (DPL), and findings on exploratory laparotomy or observation were used for confirmation or as a reference for intra-abdominal injury. Hemodynamic instability: Systolic blood pressure (SBP) less than 90 mm Hg on arrival to the ER, decrease in the SBP during ER evaluation to less than 90 mm Hg, and not responding to resuscitative measures. RESULTS During a 7-year period, 2,980 patients were evaluated by the trauma service in the ER. In all, 850 patients were identified who did not have FAST results recorded in the registry. These patients were excluded, which left 2,130 patients who underwent a FAST examination. The FAST was inconclusive in 18 (0.8%) patients, and 7 (0.3%) patients were dead on arrival, leaving a total of 2,105 patients or 70% of our trauma patients available for analysis. Of the 18 patients with inconclusive FAST scan, a follow-up CT was conducted in 15 patients; rib and pelvic fractures were the most common findings. Of the 93 patients with a positive FAST (4%), 4 patients did not have any injuries demonstrable by CT abdomen/pelvis, and 1 patient had a negative exploratory laparotomy (Table I). This produced a false positive rate of 5/93 or 5%. All false positive cases were blunt trauma victims. A true positive FAST was present in 88/93 (92%) patients. These findings were confirmed by CT in 70

3 Volume 148, Number 4 Natarajan et al 697 Table I. Results of patients with positive FAST True positive scan False positive scan FAST(+), CT (+) 70 FAST (+), CT ( ) 4 FAST (+), DPL (+) 1* FAST (+), DPL( ) 0 FAST (+), Ex Lap (+) 17* FAST (+), Ex Lap ( ) 1 Total 88 Total 5y *Were either hemodynamically unstable or had penetrating trauma. ywere hemodynamically stable and had blunt trauma. Table III. Results in patients with negative FAST examinations True negatives False negatives FAST(--), CT(--) 1,201 FAST ( ), CT (+) 104 FAST (--), DPL(--) or 0 FAST ( ), DPL (+) 1 Ex Lap (--) FAST (--), Observation 695 FAST ( ), Ex Lap (+) 13 Total 1,896 Total 118 Table II. Findings in patients with true positive FAST scans Stable Unstable Total Blunt Penetrating Total Table IV. Condition of patients with false negative FAST scans Stable Unstable Total Blunt Penetrating Total patients, by DPL in 1 patient, and by exploratory laparotomy in 17 patients (Table I). These 18 patients with a true positive FAST who directly had an exploratory laparotomy or DPL without a preceding CT were either hemodynamically unstable or had a penetrating injury. Among patients who had a CT, 9/70 had a penetrating injury but were stable, whereas 61/70 patients had a blunt injury. Of the 61 patients, 4 had blunt injury and were hemodynamically unstable on arrival to the ER. They responded to resuscitation and then underwent a CT of the abdomen. The other 57 patients were hemodynamically stable throughout (Table II). True negative FAST were present in 1,894 patients. Of these patients, FAST findings were confirmed by CT in 1,201 patients. In all, 695 patients were observed successfully, and no subsequent investigation was conducted for confirmation of the FAST finding. They had no additional problems in follow-up. In all, there were 118 false negative FAST examinations (Table III); 104 of these 118 patients were found to have injuries on CT, 1 had a positive DPL, and 13 had positive findings on direct exploratory laparotomy. Of the 104 patients with the false negative FAST and positive CT, 30 patients underwent exploratory laparotomy. The rest of the patients were managed conservatively. During exploratory laparotomy, 12 patients had spleen injuries, 9 patients had liver injuries, 5 patients had urinary system injuries, 3 patients had pelvic injuries, 6 patients had diaphragm injuries, 2 patients had vascular injuries, and 12 patients had mesenteric/bowel injuries. The patient with the positive DPL had blunt trauma and was unstable---he went on to have an exploratory laparotomy. Of the 13 patients who had exploratory laparotomy directly, 3 patients had blunt trauma and were hemodynamically unstable, and10 patients had a penetrating injury and were stable. Of the 104 patients with negative FAST and positive CT, there were 97 stable patients; 87 patients had blunt injuries and 10 patients had penetrating injuries. There were 7 unstable patients; 5 patients had blunt injuries and 2 patients had penetrating injuries. Overall, 96/118 patients had blunt mechanism of injury and 22/118 patients had penetrating injuries (Table IV). For 87 HSBT patients with false negative FAST, the injuries on CT are listed in Table V. Nineteen (22%) of these patients underwent a subsequent exploratory laparotomy. The findings at laparotomy include 10 patients with splenic injuries, 5 patients with liver injuries, 2 patients with kidney injuries, 9 patients with bowel injuries, 1 patient with an open pelvic fracture, 1 patient with a vascular injury, and 3 patients with diaphragmatic injuries. In our study, FAST had an overall sensitivity of 43%, a specificity of 99%, and positive and negative predictive values of 95% and 94%, respectively. The rate of accuracy was 94%. Of the 2,105 patients included in the study, 214 patients had penetrating trauma and 1,891 patients had blunt trauma. In addition, 1,832 patients were hemodynamically stable and had blunt abdominal trauma. True positive FAST were found in 60 patients, false positive in 4 patients, true negative in 1,681 patients, and false negative in 87

4 698 Natarajan et al October 2010 Table V. Missed injuries in hemodynamically stable blunt trauma patients Injuries found on CT Number Spleen 30 Liver 11 Pelvic injury 4 Bowel/mesentery 9 Urinary system 12 Retroperitoneal hematoma 2 Diaphragm 3 Adrenal 1 Vascular 1 Free fluid (nonspecific) 3 Combination of injuries 23 patients. For this group of patients, in our study FAST had a sensitivity of 40.8%, a specificity of 99%, and positive and negative predictive values of 94% and 95%, respectively. The rate of accuracy was 95%. The FAST scan had a sensitivity, specificity, and positive and negative predictive values of 57%, 97%, 92%, and 80%, respectively, for patients with unstable blunt trauma. Only 214 patients with penetrating trauma were assessed by the FAST in our study. In the stable penetrating trauma patients, the FAST had sensitivity, specificity, and positive and negative predictive values of 43%, 100%, 100%, and 90%, respectively. Only 8 patients were unstable, had a penetrating trauma, and had a FAST. We, therefore, did not analyze the results of the FAST for this group. DISCUSSION Evaluation and management of blunt abdominal trauma continues to be a major challenge for trauma surgeons. FAST conducted emergently in the trauma setting is now used widely in the United States to evaluate hemodynamically unstable blunt trauma patients as it gives a rapid assessment of injuries. 1-7 Its utility in the hemodynamically stable blunt trauma (HSBT) patient, however, remains questionable. 8 Although FAST has been shown in multiple studies to be sensitive for detection of free intraperitoneal fluid, it is not reliable for the diagnosis of solid organ or retroperitoneal injuries One notable limitation is that the test is operator dependent. 10 In obese patients and those with subcutaneous emphysema, the study is limited. 12,13 In patients with pelvic fracture, its role remains unclear. 6,14,15 If sensitivity and specificity of FAST approach that of CT, then its use in terms of time and resources is high; however, if they are much lower than that of CT, injuries would be missed if the FAST is not followed by CT. 10,16-18 In such cases, doubling tests would lead to using more time and resources and conducting only CT might be more prudent. In this study, our aim was to evaluate the efficacy of the FAST in directing the management of HSBT after arrival to the emergency department. The overall FAST results showed a specificity and positive and negative predictive values of 99%, 95%, and 94%, respectively; however, the sensitivity was found to be 43%, which is less than that found in literature. The sensitivity of the FAST in the literature varies between 63% and 96%. 10,19-21 In the scenario of the HSBT patients, our FAST scan results showed a specificity and positive and negative predictive values of 99%, 94%, and 95%, respectively. The sensitivity was only 41%. Few studies have evaluated the FAST for this particular situation. Of note, Lee et al 5 evaluated the use of ultrasonography for the triage of blunt abdominal trauma patients for exploratory laparotomy. Their results for the normotensive patients showed a sensitivity, specificity, and negative and positive predictive values of 85%, 96%, 99%, and 96%, respectively, for the FAST study. The difference for this could be the greater percentage of solid organ and bowel injuries found in our study. The study by Lee et al 5 concentrated on triaging patients for laparotomy, whereas the aim of our study was to evaluate the efficacy of the FAST in detecting injuries. In a study similar to ours, Miller et al 22 showed a sensitivity, specificity, negative and positive predictive values, and accuracy rates of 42%, 98.7%, 67%, 93%, and 92%, respectively, for the FAST examination. They concluded, as we did, that the FAST examination is not a good screening tool for evaluation of the HSBT patients. Of 1,832 HSBT patients, 87 (5%) had false negative scans with missed injuries, and 21.8% of these patients needed operative intervention. Solid organ injury accounted for 55% of missed single organ injuries and 78% of patients with multiple organ injuries. Bowel injury accounted for 12% of missed single organ injuries. Ultrasonographic evaluation of these injuries in the absence of intraperitoneal fluid has proven to be unreliable Although a trend toward conservative management of solid organ injuries has occurred, it is important that these injuries be recognized, so that they can be followed closely and appropriate treatment can be instituted if needed. CT has several advantages. It has a sensitivity of % for diagnosis of injury in blunt abdominal trauma. 8 It helps in localizing and grading injuries,

5 Volume 148, Number 4 Natarajan et al 699 which is critical in making decisions regarding management. 10 It is less dependent on the operator. The images are more complete and reproducible. CT is not limited by bowel gas, superficial wounds, body habitus, or subcutaneous emphysema. In a multicenter, prospective trial, Livingston et al 23 studied 2,299 patients who underwent CT after blunt abdominal injury. They concluded that patients with a negative abdominal CT and blunt trauma do not benefit from hospital admission or prolonged observation. CT also has limitations. The efficacy of CT in the diagnosis of bowel injury has been controversial, which was a major limitation of CT. 24 With better equipment and protocols, however, the sensitivity of CT in this situation has improved. In their review article, Becker et al 16 quote a sensitivity of % overall for detecting injury to the gastrointestinal tract. The presence of unexplained free fluid, extraluminal gas, focal bowel wall thickening, streaky density of mesentery, and extravasation of oral contrast material are red flags for these injuries. 16 CT cannot be used in unstable or pregnant patients. It exposes patients to ionizing radiation; however, CT remains the gold standard for evaluation of the blunt trauma patient. At our institute, CT of the abdomen and pelvis is done in all HSBT patients where intra-abdominal or pelvic injuries are suspected irrespective of the FAST scan findings. The advantage of continuing FAST in HSBT patients would be the experience gained by surgeons with the use of ultrasonography. This study has several important limitations. This retrospective study was used to assess the efficacy of FAST in HSBT; 695 patients were observed without subsequent investigations to detect injuries. Though these patients remained stable, we do not have a confirmation of the findings on FAST examination. Thus, in reality they may not belong to the true negative group. Follow-up data on all these patients were not available. We, therefore, do not know whether the patients who were lost to follow-up had missed injuries. At our institute, no specific algorithm is used to manage HSBT patients, and the decision for additional investigation was made on a case-bycase basis. In conclusion, in the setting of the unstable patients in which time is of the essence, FAST is a rapid bedside investigation that can be used before deciding on whether operative intervention was needed. In contrast, in the HSBT patient, given the poor sensitivity of the FAST as a screening test, a more reliable method is needed to ensure that injuries are not missed. CT seems to play a major role in this situation. Following every FAST with a CT would lead to using more resources and time. Thus, whenever an injury is suspected in a HSBT patient, it would be more prudent for these patients to undergo a CT rather than a FAST to avoid missing injuries. It also raises the question of FAST being performed by either radiologists or formally training surgery residents. Until then, decisions made on the basis of FAST in HSBT patients may lead to increased morbidity and mortality. A large multicenter trial is needed to evaluate the effectiveness of the FAST in the HSBT setting. REFERENCES 1. Bode PJ, Edwards MJ, Kruit MC, van Vugt AB. Sonography in a clinical algorithm for early evaluation of 1671 patients with blunt abdominal trauma. AJR Am J Roentgenol 1999; 172: Brown MA, Casola G, Sirlin CB, Patel NY, Hoyt DB. Blunt abdominal trauma: screening US in 2,693 patients. Radiology 2001;218: Farahmand N, Sirlin CB, Brown MA, Shragg GP, Fortlage D, Hoyt DB, et al. Hypotensive patients with blunt abdominal trauma: performance of screening US. Radiology 2005; 235: Hoffmann R, Nerlich M, Muggia-Sullam M, Pohlemann T, Wippermann B, Regel G, et al. Blunt abdominal trauma in cases of multiple trauma evaluated by ultrasonography: a prospective analysis of 291 patients. J Trauma 1992;32: Lee BC, Ormsby EL, McGahan JP, Melendres GM, Richards JR. The utility of sonography for the triage of blunt abdominal trauma patients to exploratory laparotomy. AJR Am J Roentgenol 2007;188: McGahan JP, Richards J, Gillen M. The focused abdominal sonography for trauma scan: pearls and pitfalls. J Ultrasound Med 2002;21: McKenney MG, Martin L, Lentz K, Lopez C, Sleeman D, Aristide G, et al. 1,000 consecutive ultrasounds for blunt abdominal trauma. J Trauma 1996;40:607-10; discussion Griffin XL, Pullinger R. Are diagnostic peritoneal lavage or focused abdominal sonography for trauma safe screening investigations for hemodynamically stable patients after blunt abdominal trauma? A review of the literature. J Trauma 2007;62: Poletti PA, Kinkel K, Vermeulen B, Irmay F, Unger PF, Terrier F. Blunt abdominal trauma: should US be used to detect both free fluid and organ injuries? Radiology 2003; 227: Poletti PA, Wintermark M, Schnyder P, Becker CD. Traumatic injuries: role of imaging in the management of the polytrauma victim (conservative expectation). Eur Radiol 2002;12: Shanmuganathan K, Mirvis SE, Sherbourne CD, Chiu WC, Rodriguez A. Hemoperitoneum as the sole indicator of abdominal visceral injuries: a potential limitation of screening abdominal US for trauma. Radiology 1999;212: Dolich MO, McKenney MG, Varela JE, Compton RP, McKenney KL, Cohn SM. 2,576 ultrasounds for blunt abdominal trauma. J Trauma 2001;50: Kornezos I, Chatziioannou A, Kokkonouzis I, Nebotakis P, Moschouris H, Yiarmenitis S, et al. Findings and limitations

6 700 Natarajan et al October 2010 of focused ultrasound as a possible screening test in stable adult patients with blunt abdominal trauma: a greek study. Eur Radiol 2010;20: Friese RS, Malekzadeh S, Shafi S, Gentilello LM, Starr A. Abdominal ultrasound is an unreliable modality for the detection of hemoperitoneum in patients with pelvic fracture. J Trauma 2007;63: Sirlin CB, Brown MA, Deutsch R, Andrade-Barreto OA, Fortlage DA, Hoyt DB, et al. Screening US for blunt abdominal trauma: objective predictors of false-negative findings and missed injuries. Radiology 2003;229: Becker CD, Mentha G, Schmidlin F, Terrier F. Blunt abdominal trauma in adults: role of CT in the diagnosis and management of visceral injuries. Part 2: gastrointestinal tract and retroperitoneal organs. Eur Radiol 1998;8: Becker CD, Mentha G, Terrier F. Blunt abdominal trauma in adults: Role of CT in the diagnosis and management of visceral injuries. Part 1: liver and spleen. Eur Radiol 1998; 8: Helling TS, Wilson J, Augustosky K. The utility of focused abdominal ultrasound in blunt abdominal trauma: a reappraisal. Am J Surg 2007;194:728-32; discussion Forster R, Pillasch J, Zielke A, Malewski U, Rothmund M. Ultrasonography in blunt abdominal trauma: influence of the investigators experience. J Trauma 1993;34: McGahan JP, Richards JR. Blunt abdominal trauma: the role of emergent sonography and a review of the literature. AJR Am J Roentgenol 1999;172: Sirlin CB, Brown MA, Andrade-Barreto OA, Deutsch R, Fortlage DA, Hoyt DB, et al. Blunt abdominal trauma: clinical value of negative screening US scans. Radiology 2004; 230: Miller MT, Pasquale MD, Bromberg WJ, Wasser TE, Cox J. Not so FAST. J Trauma 2003;54:52-9; discussion Livingston DH, Lavery RF, Passannante MR, Skurnick JH, Fabian TC, Fry DE, et al. Admission or observation is not necessary after a negative abdominal computed tomographic scan in patients with suspected blunt abdominal trauma: results of a prospective, multi-institutional trial. J Trauma 1998;44:273-80; discussion Peitzman AB, Makaroun MS, Slasky BS, Ritter P. Prospective study of computed tomography in initial management of blunt abdominal trauma. J Trauma 1986;26: DISCUSSION Dr David Mulder (Toronto, Quebec, Canada): The authors have done an examination of their data from an ongoing registry and two important groups emerge. The first is the true positive FAST exam. There were 88 patients in that group, and every single one was confirmed. The injuries were subsequently confirmed by a CT scan and, therefore, perhaps were unnecessary. But more importantly were the false negative FAST exams, and they were seen in 118 patients. And as you said, 20% or more had to undergo a laparotomy and would have suffered dire consequences with these as missed injuries. I have 2 or 3 questions here. Have these results changed your institution s policy in terms of the FAST exam in the hemodynamically stable patient with blunt trauma? What is your protocol for training the surgical residents to carry out this exam? Is there any radiology involvement? The third question that I would like to pose is, is there any role for the ultrasound exam as a baseline for following subsequent conservative management of solid organ injury? The authors have asked the rhetorical question in the title of their paper, and I guess the answer is a resounding no, and I would say that CT scan trumps FAST exam every time. Dr Bala Natarajan (Omaha,NE):Atourinstitute,the policy has yet not changed. But I think the next step for us would be to design a prospective study where we will evaluate exam results after assigning patients to different groups and seeing how the results come out in the HSBT patients. The FAST exam was performed by surgery residents under the supervision of the trauma surgeons. The trauma surgeons were credentialled on the FAST scan skills by the trauma director, who was credentialled by the radiology ultrasound specialist. The role of the ultrasound as baseline for solid organ injuries. Ultrasound has been proven, at least the FAST exam has been proven, to be unreliable for diagnosis of solid organ injuries. It only detects free intra-abdominal fluid. We would have to rely on the CTscan for detection of solid organ injury. Dr Kathryn Tchorz (Dayton, OH): We know the study was a retrospective one of a level 1 trauma center looking at their patients, 2,100, who had an ultrasound performed by the surgical residents, and then compared with the definitive study, whether it be CT, DPL, and/or exploratory laparotomy. Specifically, the authors wanted to test their ability to detect injury on hemodynamically normal patients. I have a few comments and questions. First, we know that the goal of the ultrasound is to identify hemoperitoneum and/or hemopericardium, and that was the original diagnostic role of this. It is not to determine injury or degree of injury. And one can do that. But additional training needs to be done with that. The study objective is here really my first concern. And the second is actually the denominators in looking at this data set especially for the false negative FAST with positive injuries. The diagnostic studies should evaluate this: Is there hemoperitoneum on these studies? Yes or no. Not the degree of injury. And having a retroperitoneal injury does not indicate hemoperitoneum. So that is my one concern. Again, hemodynamic normality based on very obvious findings of shock with a systolic blood pressure of 90 we know can be challenging. I was very surprised that you did not include the indeterminate patients, and that they were actually a very low number. Most of the time, our indeterminates are very high, mostly because of morbid obesity in our country. Actually, the indeterminate FAST can be extremely helpful because something is obviously wrong with the patient. They have subcutaneous emphysema, or they have a pelvic fracture, something is wrong that we cannot image the patient properly. And we know, from all the research, we need to do additional studies on them, and that is nothing new. We know they can be highly associated with occult injury. I would really like to know how your group

7 Volume 148, Number 4 Natarajan et al 701 continues quality improvement on looking at the ultrasounds, who monitors these, how is the teaching performed, especially with your indeterminate FAST, who reviews them and what were the reasons for indeterminate? My real concern, looking at this, is that I do not think that your conclusions support your study. It is well known that ultrasound is not a specific modality, and the limits of ultrasound---at least, looking to the ultrasound right now---are clearly what you found. However, you report a 95% negative predictive value, which is actually very good for a screening test. However, in that number, we have a lot of patients who actually were followed by clinical exam, so they do not have a confirmatory test. Please comment on that. Dr Bala Natarajan (Omaha, NE): The first question was about the aims of our study. We wanted to do our study in hemodynamically stable patients. Even though the FAST exam has been proven to be useful in unstable patients, we have expanded to the blunt trauma stable patients in many centers, and we wanted to see what the effectiveness of the FAST exam was in detecting injuries in this group of patients. In this group of stable patients we do have time for further investigations and to determine the extent of their injuries. We wanted to see whether the FAST was adequate to evaluate these injuries. The second question was about the quality control of the trauma team in interpreting the FAST exams and we do not have a program where we evaluate the quality control of the resident. However, like I mentioned before, the trauma director is signed off by the radiologist, and he, in turn, trains the surgery staff and they train the residents. All the FAST exams are done in the presence of the trauma surgeons. As for your question about whether we should use the confirmatory test only in the presence of free fluid. These are patients who are stable, and they have blunt trauma, and not all of them may have free fluid in the abdomen. The aim of our study was to see whether FAST exam is picking up injuries. The limitation of the test is that it picks up only free fluid and does not pick up organ injury. In these HSBT patients we use the CT scan for confirmation of the injuries both in the presence and absence of free fluid. Dr Brian Harbrecht (Louisville, KY): If I did my math correctly, you all did about 300 FAST exams a year over the course of your study. Do you think that is a volume that is sufficient to establish and maintain expertise once you divide that by X number of residents going through your training program? With respect to the injuries that were identified, it looked like there were a substantial number of bowel injuries, diaphragm injuries, and urinary tract injuries which you included in your sensitivity and specificity analysis. Since one would not expect the FAST exam to pick up urinary tract injuries or diaphragm injuries or bowel injuries and a variety of others on your list, is that really a fair assessment? Finally, worth is a tough thing to demonstrate. Proving something is useful is one thing, but trying to definitively prove something is not useful is another. I was wondering, since this is basically an extension of your physical exam, if there were any cases that you identified where there was harm from the FAST exam to the patient, or whether it was merely not as productive of useful information as you had hoped. Dr Bala Natarajan (Omaha, NE): Thank you for those excellent questions. Our center is a level 1 trauma center. We have joint trauma programs with the University of Nebraska, so we cover 4 days of trauma and they cover 3 days, so we do see a fair number of trauma patients in those 4 days of the week that we cover. So, I think we get enough cases to train in the FAST exam. The other injuries that are affecting the results, like the urinary injuries and the bowel injuries and which are also playing a role in the calculations, are exactly the injuries that we missed in a lot of these patients, and we need a definitive test like the CT. So, in these stable patients where we have time to evaluate them properly, we need a better test rather than the FAST exam to evaluate them. You are correct that we did not find that the FAST exam was harmful to any of the patients. However, it is one more procedure that needs to be done on a patient who may not require it, and that is the purpose of our study, to evaluate its position in the stable blunt trauma patients. Dr Gerald Larson (Louisville, KY): Based on your studies now, are you going to alter your use of the FASTscan in hemodynamically stable patients? Are you going to discontinue doing the FAST scan in the stable patient? Dr Bala Natarajan (Omaha, NE): We are using the FAST exam as part of the training tool for the residents, so we are continuing to do it at this point of time. However, I think we need to do a prospective study where we will try to evaluate in this group of HSBT whether it is a useful test or not. And if we can conclusively prove that there is no use of this test in this group of patients, then we should alter our practices.