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Journal of Veterinary Emergency and Critical Care 28(5) 2018, pp 429–435 doi: 10.1111/vec.12732

Original Study

Evaluation of the agreement between focused assessment with sonography for trauma (AFAST/TFAST) and computed tomography in dogs and cats with recent trauma Andrea M. Walters, DVM, MS, DACVECC; Mauria A. O’Brien, DVM, DACVECC; Laura E. Selmic, BVetMed (Hons), MRCVS, DACVS; Sue Hartman, RT(R)CT; Maureen McMichael, DVM, DACVECC and Robert T. O’Brien, DVM, MS, DACVR Abstract

Objective – To determine the agreement between focused assessment with sonography for trauma (FAST) exams and computed tomography (CT) for the detection of pleural and peritoneal fluid and pneumothorax in animals that have sustained recent trauma. Design – Prospective study. Setting – University Teaching Hospital. Animals – Thirteen dogs and 2 cats were enrolled into the study, with 10 having sustained blunt force trauma and 5 penetrating trauma. Interventions – Abdominal FAST (AFAST) and thoracic FAST (TFAST) exams were performed by emergency room (ER) clinician or house officers and radiology house officers (radiology). TFAST evaluated for the presence of pneumothorax and pleural effusion, and AFAST evaluated for the presence of peritoneal effusion. A minimally sedated, full-body CT exam was performed on each patient and interpreted by a board-certified radiologist. The exams were performed in the same order for all patients: ER FAST, followed by radiology FAST, followed by CT, and operators were blinded to the results of the other exams. A kappa statistic was calculated to assess for agreement between the FAST exams and CT. Measurements and Main Results – The median time to perform all 3 exams was 55 minutes (range 30–150 min). There was moderate to excellent agreement between AFAST and CT for detection of free peritoneal fluid (ER K = 0.82; radiology K = 0.53), fair to moderate agreement between TFAST and CT for detection of pleural free fluid (ER K = 0.53; radiology K = 0.36), and poor agreement between TFAST and CT for detection of pneumothorax (ER K = –0.06; radiology K = –0.12). Conclusions – FAST exams reliably identify the presence of free fluid in the peritoneal and pleural cavities; however, TFAST is not a reliable method to diagnose pneumothorax in dogs and cats following trauma. (J Vet Emerg Crit Care 2018; 28(5): 429–435) doi: 10.1111/vec.12732 Keywords: effusion, glide sign, multidetector, ultrasound

Abbreviations

AFAST abdominal focused assessment with sonography for trauma CT computed tomography ER emergency room TFAST thoracic focused assessment with sonography for trauma The authors report no conflicts of interest. Address correspondence and reprint requests to Mauria A. O’Brien, Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign, 1008 West Hazelwood Dr, Urbana, IL 61802, USA. Email: [email protected] Submitted March 25, 2016; Accepted November 15, 2016.  C Veterinary Emergency and Critical Care Society 2018

Introduction Severe trauma, caused by blunt force or penetrating injury, is a common cause of morbidity in veterinary patients and often results in life-threatening damage to multiple body cavities or regions.1 In animals, blunt force trauma is associated with a 10% mortality rate, and is most frequently caused by motor vehicular trauma (MVT) or falls from a height.1–3 Penetrating trauma is associated with a mortality rate of 13% and can be a result of bite wounds, gunshot wounds, or penetrating objects.4 The body region most affected by trauma is the thorax,1,5 resulting in pulmonary contusions, pneumothorax, and hemothorax.3,6 Abdominal injury is also common in veterinary patients following trauma,1 429

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and can result in organ damage7 and intra-abdominal hemorrhage.8,9 In human medicine, computed tomography (CT) is the gold standard for diagnosis of trauma-related injuries and provides high spatial resolution, fast scan times, and the ability to produce 3-dimensional image reconstructions.10,11 Because CT scans are expensive and expose the patient to high levels of radiation,12 increased attention has been focused on the use of ultrasound in the emergency room (ER) as the primary imaging modality for the assessment of human victims of trauma.11,13–15 The most common ultrasound protocol for assessment of trauma victims is the focused assessment with sonography for trauma (FAST) scan. FAST scan protocols have been developed for evaluation of the thorax (which evaluate the pleural space for both pneumothorax and effusion) and the abdomen (which evaluate for the presence of peritoneal effusion). In people, these techniques are associated with a 90–98.1% sensitivity16,17 and 99% specificity16 for diagnosing intracavitary free fluid and a sensitivity of 92–100% and specificity of 94–99.4% for the detection of pneumothorax.15,18 FAST scans have also been evaluated in small and large animal veterinary patients following trauma.5,8,9,19 Boysen et al9 prospectively evaluated an abdominal FAST scan (AFAST) in traumatized patients and Lisciandro et al8 evaluated a protocol and scoring system to identify free fluid in the abdomen. Lisciandro et al5 also described the use of a thoracic FAST scan (TFAST) to identify pneumothorax (sensitivity 78.1%, specificity 93.0% compared to thoracic radiographs) and pleural effusion. Although the use of FAST scans in veterinary patients following trauma is increasing, there have been no studies comparing the diagnostic performance of FAST scans to full-body CT in dogs and cats having recently experienced trauma. The goal of our study was to evaluate the sensitivity and specificity of FAST scans as tools for the diagnosis of pneumothorax, pleural effusion, and peritoneal effusion in the ER. Our hypothesis was that there would be good agreement between FAST scans and CT in the identification of fluid in the peritoneal cavity, and fluid and air in the pleural space.

Materials and Methods Patients that presented to the ER between April 1 and August 31, 2014 and had undergone either blunt (eg, motor vehicle trauma or falls) or penetrating trauma (eg, bite wounds) were eligible for inclusion. Each patient underwent imaging in the following order: FAST scans in ER, FAST scans in radiology, and full-body CT scan. The study was approved by the Institutional 430

Animal Care and Use Committee and written owner consent was provided for all animals before enrolled in the study. The following parameters were recorded for all patients upon admission to the ER: heart rate, respiratory rate, rectal temperature, mucous membrane color and capillary refill time, pulse quality, blood pressure, and hemoglobin–oxygen saturation (via pulse oximetry). In addition, a 3-minute ECG was evaluated. The primary ER clinician was required to complete a separate checklist, which included questions about history and physical examination. Additional monitoring, diagnostic, and therapeutic procedures were performed at the discretion of the ER clinician and in the order that was medically appropriate for the clinical status of the patient. Prior to initiation of the study, all ER clinicians (interns, residents, and attending board-certified emergency and critical care specialists) were required to complete a minimum of 1 hour of didactic training and a hands-session on FAST scan procedures given by a board-certified veterinary radiologist (RB). In addition to the didactic portion, each ER clinician was required to complete a supervised (by RB) AFAST and TFAST scan on a normal dog. The FAST scans in the ER were performed using a C611 micro convex 4–10 mHz probe.a The ER FAST scans were performed by the primary receiving clinician, who may have been an emergency/critical care resident (2), medicine/surgery intern (2), emergency/critical care intern (1), or a board-certified emergency and critical care specialist (1). The radiology FAST scans were performed by second or third year radiology residents (3), who were blinded to the results of the initial FAST scan and under direct supervision of a board-certified radiologist (while the scans were occurring). Each patient had 1 ER clinician who performed both the AFAST and TFAST scans, and then 1 radiology resident performed both the AFAST and TFAST scans. The scans performed by the radiology residents were performed using either an 11MC4 curvilinear high frequency convex 4.2–10.2 mHz probeb or a CA123 micro convex 3–9 mHz probe.c All attempts to minimize the time between the 2 FAST scans were taken, but the clinical needs of the patient were the highest priority. Patient stabilization was allowed at any point during the imaging protocol, including, but not limited to, administration of intravenous fluids and medications, thoracocentesis, and abdominocentesis. Any clinician performing the scan was required to fill out a standardized data sheet to record their FAST scan findings and give information about the study (ie, time, date, and samples taken). FAST scan protocols for both the abdomen and thorax were based on previously described patterns,5,8 and patients were evaluated for the presence of pneumothorax, pleural effusion, pericardial effusion, and peritoneal  C Veterinary Emergency and Critical Care Society 2018, doi: 10.1111/vec.12732

Trauma: FAST scan versus CT

effusion. Because right lateral recumbency is routine for the acquisition of ECG data and ideal for ultrasonographic imaging of both the thorax5 and abdomen,8 dogs were initially placed in right lateral recumbency unless injuries prevented this positioning. Four points in the abdomen were examined for peritoneal effusion9 : (1) caudal to the xyphoid to assess between the liver lobes and diaphragm, (2) nondependent lateral flank, (3) caudally on midline adjacent to the bladder, and (4) dependent lateral flank. When scanning for effusion, the probe was held parallel to the long-axis of the body (in a cranialcaudal direction) and was fanned back and forth. The probe was then rotated 90 degrees and the process was repeated. Two points were evaluated on each side of the thorax: (1) tallest nondependent chest wall bilaterally to identify pneumothorax, and (2) cranial pleural space bilaterally to look for pleural and pericardial effusion. For identification of pneumothorax, the probe was held stationary parallel to the long-axis of the body (in a cranial-caudal direction). Pneumothorax was defined by the absence of the “slide” or “glide sign,” which is created when the visceral and parietal pleura move against each other. Effusion was defined by the identification of hypo- to anechoic fluid in the pleural space or peritoneum. The AFAST scans and 3 out of 4 of the TFAST scan sites (cranial pleural space bilaterally and the left nondependent chest wall) were performed with the animal lying in right lateral recumbency. Then, depending on the comfort and stability of the patient, the animals were shifted into sternal or left lateral recumbency and the right hemithorax was imaged. For each of the scans, the patients were sedated as minimally as necessary with analgesics or small amounts of injectable anesthetics. General anesthesia was not required for any patient and none of the patients were intubated. Hair was not clipped for any of the FAST scans, and 70% isopropyl alcohol was used to enhance the probe contact surface for most cases instead of ultrasound gel, except where the use of alcohol would be harmful or irritating to the patient (eg, extensive dermal abrasions, need for defibrillation). Given that the primary goal of the study was to determine the presence or absence of fluid and air, quantification of the size or severity of effusion or pneumothorax and identification of the type of effusion was not performed. Following the FAST scans, survey and late venous phase full body CT (from nose to tail) was performed using a 16 multislice spiral CT.d Patients were minimally manipulated from their preferred position of rest to minimize pain and stress, resulting in variable positioning for the CT imaging. The CTs were performed using a plexiglass positioning unite for small patients or Velcro straps to restrain larger patients. The parameters for the CT were as follows: 0.5 second tube rotation,  C Veterinary Emergency and Critical Care Society 2018, doi: 10.1111/vec.12732

0.9 pitch, 120 kvp, 250–320 mA (depending on patient size), and a detailed algorithm. Transverse slices (2.5mm or 5-mm thick) were acquired and reconstructed into 0.625-mm slices for reformatted transverse, sagittal and dorsal plane images, and 3-dimensional images. Intravenous contrast agentf was injected at a dose of 0.45 mL/kg and at a rate of 2 mL/sec. A maximum of 60 mL of contrast agent was administered. The CT scans were interpreted by a board-certified radiologist (RTO) who was blinded to the results of the FAST scans.

Statistical Methods Descriptive statistics were calculated for signalment and presentation of variables. Categorical variables were reported as frequency and percentages. Continuous variables were tested for normality using histograms, skewness, kurtosis, or the Shapiro–Wilk test. If normally distributed, the mean and standard deviation (SD) was reported or if nonnormally distributed the median and range (minimum–maximum value) were reported. The Kappa statistic was calculated to assess agreement between FAST scans and CT of each body part. A Kappa statistic greater than or equal to 0.81 was deemed to have excellent correlation, between 0.61 and 0.80 was characterized as good correlation, between 0.41 and 0.60 was moderate correlation, and < 0.20 was deemed to indicate poor correlation.

Results Thirteen dogs and 2 cats presenting to the ER following trauma were enrolled. The dog breeds represented in the study population consisted of mixed breed (n = 4), Siberian Husky (n = 2), and 1 of each of Miniature Pinscher, Irish Setter, Labrador Retriever, Labradoodle, Rottweiler, Shih Tzu, and Maltese dogs. Both cats were domestic short hair cats. Combining both cats and dogs, the population consisted of 8 males (4 neutered) and 7 females (4 neutered and 1 of unknown neuter status). The mean (±SD) age of enrolled dogs and cats was 5.2 ± 4.2 years old, and the mean (±SD) weight was 18.8 ± 13.2 kg. Nine animals (60%) presented directly to the ER, and 6 animals (40%) were referred to the ER after initial assessment at their referring veterinarian. Nine animals (60%) had injuries to ࣙ2 body cavities, and 6 animals (40%) only had injury to 1 body cavity. There were 10 animals (67%) that had suffered blunt force trauma (9 motor vehicular trauma and 1 fall from a height) and 5 animals (33%) that had suffered penetrating trauma due to bite wounds. The time of trauma was known in 14 of the animals, and the remaining 1 was estimated based on the owners estimate as to the earliest possible time it could have 431

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Table 1: Summary of injuries detected by CT in 15 animals (13 dogs and 2 cats) following blunt or penetrating trauma Musculoskeletal (n = 12; 80%)

Vertebral fracture/luxation (n = 5; 31%) Limb fractures (n = 3; 20%) Sacral fracture (n = 2; 13%) Subcutaneous emphysema (n = 2; 13%) Soft tissue wounds (n = 1; 6%)

Thoracic (n = 8; 53%)

Pneumothorax (n = 6; 38%) Pleural effusion (n = 6; 38%) Pulmonary contusions (n = 3; 19%) Pneumomediastinum (n = 3; 19%) Rib fractures (n = 2; 13%) Traumatic bulla (n = 2; 13%) Lung lobe herniation (n = 1; 6%)

Abdomen (n = 4; 27%)

Peritoneal effusion (n = 4; 27%) Hematoma within organs (n = 1; 7%) Intestinal herniation (n = 1; 6%)

Head and neck (n = 3; 20%)

Traumatic brain injury (n = 3; 20%) Ruptured globe (n = 1; 6%) Laryngeal tear (n = 1; 6%) Nasal bone fracture (n = 1; 6%)

CT, computed tomography.

happened. The median (range) time from trauma to presentation to the ER was 1.5 hours (0.3–72.0 h) and the median time to perform all 3 scans (from ER FAST through CT) was 55.0 minutes (30–150 min). The median time from presentation to the hospital to the start of the ER FAST scans was 54.0 minutes (0.0–80.0 min), from the completion of the ER FAST scan to the start of the radiology FAST scan was 30.0 minutes (10.0–130.0 min), and from the completion of the radiology FAST scan to start of CT scan was 15.0 minutes (5.0–85.0 min). Due to injuries, pain, or stress, 5 patients only had 1 side imaged to evaluate for the presence of pneumothorax, 2 patients only had 1 side imaged to detect the presence of pleural effusion, and 1 patient did not have the pleural space imaged at all (and was not included in the statistical analysis for TFAST effusion). A summary of the injuries identified by evaluation of the CT scans is presented in Table 1. The results of the Kappa analyses are summarized in Table 2. AFAST had moderate (radiology) to excellent (ER) correlation to CT for detection of peritoneal effusion. All 3 of the animals with peritoneal effusion detected on ER AFAST scan also had peritoneal effusion identified on the CT scan. The radiology AFAST scan detected 5 patients with peritoneal effusion, however only 3 of these had effusion identified by analysis of the CT scan. In both cases, analysis of the CT scan suggested the presence of peritoneal effusion in 1 animal each in which the ER and radiology AFAST exams had not detected fluid. TFAST had fair (radiology) to moderate (ER) correlation to CT for the detection of pleural effusion. Of the 3 432

patients with pleural effusion identified by ER TFAST, CT confirmed the presence of pleural effusion in all 3 patients, but 3 additional patients with pleural effusion identified by CT scan did not have fluid identified on the ER TFAST scan. Of the 2 patients with pleural effusion detected by the radiology TFAST scan, CT confirmed both cases, but found 4 additional patients with pleural effusion. TFAST had poor (radiology and ER) correlation to CT for detection of pneumothorax. Of the 3 patients that had a pneumothorax identified on the ER TFAST scan, only 1 was confirmed by CT, and CT identified 5 additional patients with pneumothorax that was not detected by the ER TFAST scan. Only 1 pneumothorax was identified on radiology TFAST, and this was not identified by analysis of the CT scan of that particular animal. Thirteen animals received analgesic medications in the ER prior to their FAST scans, all of which consisted of intravenous intermittent boluses or constant rate infusions of full opioid agonists. In addition, 1 animal was given a bolus of lidocaine prior to the ER FAST scans, and another animal required an IV bolus of propofol to provide sedation during the radiology FAST scans. All animals received sedation prior to the CT scan. Intravenous sedative protocols included only full opioid agonistsg (n = 8), full opioid agonist and a benzodiazepineh (n = 2), full opioid agonist and an alpha-2 receptor agonist drugi (n = 2), full opioid agonist and intermittent IV boluses of propofolj (n = 2), and full opioid agonist, a benzodiazepine, and intermittent IV boluses of propofol (n = 1). Additional IV medications provided in the ER prior to imaging included lactated Ringer’s solutionk (n = 9), mannitoll (n = 3), ampicillin and sublactamm (n = 2), and VetStarchn (n = 1). Of the cases assessed by ER clinicians, 3 were assessed by a medicine/surgery intern, 1 by an emergency/critical care specialty intern, 7 by an emergency/critical care resident, and 4 by a board-certified emergency/critical care specialist.

Discussion AFAST had the highest agreement with CT for diagnosis of peritoneal effusion, followed by TFAST to diagnose pleural effusion. However, TFAST did not prove to be a reliable diagnostic tool to identify pneumothorax in trauma patients, when compared to CT. AFAST performed in the ER had excellent agreement with CT for diagnosis of free peritoneal fluid. AFAST scans have been described as an accurate and easily learned diagnostic technique for identification of peritoneal effusion in veterinary species caused by leakage of urine or bile, vascular injury, or rupture of an abdominal viscus.8,9,20 The presence of peritoneal effusion in  C Veterinary Emergency and Critical Care Society 2018, doi: 10.1111/vec.12732

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Table 2: Summary of agreement between FAST scans and CT performed in 15 animals (13 dogs and 2 cats) following blunt or penetrating trauma. FAST scans were performed either by emergency room clinicians (ER department) or by radiology residents (radiology department), and kappa scores were calculated assuming the results of the CT as a gold diagnostic standard

Imaging modality

Department

FAST negative CT positive

FAST positive CT negative

AFAST (presence of peritoneal effusion)

ER Radiology ER Radiology ER Radiology

1 1 3 4 5 6

0 2 0 0 2 1

TFAST (presence of pleural effusion) TFAST (presence of pneumothorax)

Kappa 0.82 0.53 0.53 0.36 −0.06 −0.12

FAST, focused assessment with sonography for trauma; AFAST, abdominal focused assessment with sonography for trauma; TFAST, thoracic focused assessment with sonography for trauma; CT, computed tomography; ER, emergency room.

dogs and cats following trauma has been linked to decreased survival and increased time to discharge from the hospital.8 Progressive peritoneal effusion may indicate ongoing hemorrhage.8,21 Early identification of free abdominal fluid is imperative to determine the extent of injuries, monitor the animal’s progression, and allow for initiation of specific treatment. Up to 20% of dogs with hemoperitoneum require a blood transfusion9 and 5% will require emergency surgery to control hemorrhage.1 The agreement between radiology AFAST scans and CT was lower than that of the ER AFAST scans and CT. Two animals had peritoneal effusion identified by radiology AFAST only that was not seen on CT. Ultrasound may be a more sensitive imaging modality than CT for detection of small amounts of fluid, particularly in the hands of skilled clinicians. Given the method by which kappa is calculated, these cases were interpreted as “false positives” and resulted in a decreased kappa value, although they may have instead indicated a failure of the CT scan to detect the presence of this fluid. Our results showed fair to moderate agreement between TFAST and CT for the detection of pleural effusion. Human studies have suggested that TFAST is an easily learned, minimally user dependent,22 and accurate diagnostic modality for the detection of hemothorax after trauma, with a sensitivity of 92% and specificity of 100%.23 In our study, the difference between AFAST and TFAST in the ability to identify fluid in the abdomen or thorax may indicate that thoracic ultrasound is technically more challenging than abdominal ultrasound in veterinary patients, or that the sites used may not be ideal for fluid detection in all patients. The diaphragmaticohepatic (or subxyphoid) window is an additional view that has been described for detection of pleural and pericardial effusion in veterinary patients.24 Future prospective studies are needed to evaluate the utility of adding this additional view to TFAST for identification of pleural effusion.  C Veterinary Emergency and Critical Care Society 2018, doi: 10.1111/vec.12732

In contrast to a previous report,5 this study did not find TFAST to be a reliable diagnostic tool for the identification of pneumothorax in veterinary patients. There are several potential reasons for this discrepancy. This study compared TFAST to CT, while the previous study compared TFAST to thoracic radiographs. In human patients, radiographs have been reported to miss 11–64% of pneumothorax diagnoses compared to CT.15,18,25,26 A veterinary study has suggested that thoracic radiographs obtained using horizontal beam views improved the sensitivity of radiographs for detection of pneumothorax,27 and these views were not evaluated in the previous TFAST study.5 The TFAST scan is also a more technically demanding procedure compared to AFAST in both human13,28–31 and small and large animal veterinary medicine,5,19 with a reported sensitivity of 45.4% for less experienced users compared to 95.2% for an experienced user in veterinary medicine.5 It is possible that the training program implemented for the current study was not sufficient to provide enough clinical experience to result in successful detection of all cases of pneumothorax. Although it has been reported that TFAST has a high sensitivity for detection of pneumothorax in human patients following blunt force trauma,32 a previous veterinary report concluded that the accuracy of TFAST for the diagnosis of pneumothorax was higher in patients with penetrating trauma compared to blunt force trauma, with sensitivities of 93.3% and 64.7%, respectively.5 It has also been reported that a small pneumothorax may be easily missed on ultrasound,33 although without quantifying the size of pneumothorax, we are unable to say if this played a role in our study. Although thoracic ultrasound is a sensitive and specific diagnostic modality for pneumothorax in people,11 the results of the current study may call into question the utility of TFAST for the diagnosis of pneumothorax in veterinary patients. Although FAST scans are arguably more sensitive for detection of small amounts of intracavitary free fluid, CT is more sensitive for diagnosis of pneumothorax. CT 433

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eliminates structural superimposition, is less dependent on user experience and patient characteristics, and provides more complete images of all aspects of a particular body cavity. In addition, Hounsfield units can be used to provide objective measurements to differentiate fluid, air, bone, and a variety of soft tissues. In the human ER, full body CT scan results have been shown to change treatment protocols in 19%34 and 32%35 of cases, and are significantly associated with decreased mortality, as the CT is able to identify more occult injuries that may require early interventions.12 New CT technology has significantly decreased the time needed to perform scans, and an average awake or minimally sedated fullbody CT in the authors’ hospital takes only minutes. It is also important to emphasize that most of the animals were adequately sedated during the CT scan with a neuroleptanalgesic protocol. None of the animals required intubation or inhalant anesthesia, and no complications from sedation were noted in any of the animals. There are several other reports of the use of CT to produce good quality images in awake or mildly sedated animals, with minimal motion artifact.36–39 The limitations of this study pertain mostly to uncertainties of clinical cases and small sample size. In this study, the animals’ safety and treatment needs were placed above strict adherence to the study protocol. For a variety of reasons including stress, pain, vertebral fractures, and respiratory distress, many of the patients required changes in position between the 2 fast scans, so many were not in the same position for all of the scans. Therefore, a comparison of the position of fluid within the chest and abdomen between the different imaging modalities could not be performed. Also, 2 therapeutic thoracocentesis procedures (to treat pneumothorax) were performed prior to the FAST scans, with one being performed at the ER, and another at the referring veterinary clinic prior to presentation to the ER. In addition, 1 animal had a diagnostic thoracocentesis performed after the ER FAST scan was completed to try and obtain a sample of pleural effusion; however, no sample was obtained by this procedure. Although this may have introduced bias to the ER TFAST scans, this would not have affected the blinded radiology TFAST scans as the radiology residents were unaware of the prior thoracocentesis performed in ER. Also, adding to this bias is the fact that radiographs were performed on 4 animals (1 of which had a thoracocentesis described above) at referring veterinary clinics prior to presentation to the ER, which may have provided a suspected diagnosis prior to FAST scans. However, only 2 of the cases had 2-view thoracic radiographs available for evaluation on presentation. For 1 other dog, the ER clinician did not have access to the thoracic radiographs and an additional dog only had a minimally collimated full body 434

lateral radiograph available for evaluation, which was difficult to interpret. The authors also attempted to minimize the amount of time between scans; however, given the clinical nature of the study, patient needs occasionally caused delays between scans. It is possible that air or effusion may have accumulated during the time delay that occurred between the imaging studies. However, the authors feel that this methodology, albeit potentially biased, reflects real life interpretation and the conclusions are relevant. Due to external injuries, not all of the TFAST scans were performed bilaterally. Of the unilateral scans for pneumothorax, 4 out of 5 showed no signs of pneumothorax on both TFAST and CT. One dog had a bilateral pneumothorax identified on CT, so this should not have affected the results, as a pneumothorax was present on the one side that was imaged. Of the animals that underwent unilateral TFAST scans, 1 did not have evidence of pleural effusion on TFAST or CT. The other patient did not have pleural effusion identified on TFAST but did have effusion present on the CT exam, so the lack of bilateral TFAST may have affected the ability to detect fluid on the nonimaged side. Human medicine dictates that appropriate treatment be implemented immediately after trauma has occurred to minimize patient mortality.12,40 The initiation of appropriate treatment relies on both a timely and accurate diagnosis of injuries. In veterinary patients, a full-body CT scan allows for detection of pneumothorax, pleural, and peritoneal effusion, and a complete evaluation of trauma-based injuries. FAST ultrasound exams continue to be a useful modality for rapid identification of free peritoneal and pleural fluid, but TFAST appears to be an inaccurate method for the diagnosis of pneumothorax. More sensitive imaging diagnostics, such as horizontal beam thoracic radiography or CT, should be considered as a part of the initial imaging protocol for trauma patients with respiratory difficulty.

Footnotes a b c d e f g h i j k l m n

Sonoscape S8, Providian Medical Equipment LLC, Willowick, OH. Aplio 300, Toshiba American Medical Systems Inc., Tustin, CA. MyLab 70 XVG, Esaote, Indianapolis, IN. Lightspeed 16, GE Healthcare, Waukesha, WI. VetMouse Trap, Universal Medical Systems Inc., Solon, OH. Omnipaque 300, GE Healthcare, Princeton, NJ. Fentanyl Citrate, Hospira, Inc., Lake Forest, IL; Methadone hydrochloride, Mylan Institutional LLC, Rockford, IL. Diazepam, Hospira, Inc., Lake Forest, IL; Midazolam, Hospira, Inc., Lake Forest, IL. Dexmedetomidine hydrochloride, Zoetis, Inc., Parsippany, NJ. PropoFlo, Zoetis, Inc., Parsippany, NJ. Lactated Ringer’s Solution, ACE Surgical Supply Co. Inc., Brockton, MA. 25% Mannitol, Hospira, Inc., Lake Forest, IL. Ampicillin and Sublactam, Pfizer, Inc., New York, NY. VetStarch, 6% Hydroxyethyl Starch 130/0.4, Abbott Laboratories, North Chicago, IL.

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