The Future of Continuing Education in Diagnostic Imaging

Mass Casualty & Trauma Radiography

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Authors: Karen Vieira, PhD, MSM & Deirdre O'Donnell, M.Sc.

Abstract: Mass casualty is a term referring to when a high volume of patients visit a care facility in the same space of time. It may be related to extreme events carrying a high risk of severe injury such as natural disasters, incendiary attacks or military combat. Many patients involved in such events may emerge with life-threatening injuries in need of immediate attention. Others may be left with trauma that is not life-threatening, but can have long-term effects on life quality and functional status. The process of categorizing these patients in terms of priority for emergency care is known as triage. Imaging is an effective strategy in determining the severity of trauma. This article will describe triage and the roles played by imaging in assessing patients presenting with trauma that may result from mass casualty. It will also describe the evaluation of treatment for a severe trauma, and how imaging relates to this.

Triage

 

  1. History and Current Procedures

 

Triage is the process of assigning priority to patients for further treatment. This is normally applied to patient assignment in emergency medical settings and situations. The term may also be applied to the process of distinguishing patients with benign growths from those with malignant tumors in greater need of surgery [1]. The decisions that affect triage are obviously determined by the severity of injuries, symptoms or other events presented by an individual patient. Other factors may include resources, time and the availability of specialty staff such as surgeons capable of administering the treatment needed for serious casualties. The nature of these casualties is also an important factor in the determination of triage. A healthcare professional responsible for triage is obliged to effectively conserve life in approving patients for treatment. In some mass casualty situations, the professional must distinguish between patients likely to survive as a result of treatment and those who will not. These difficult and multifactorial choices may result in cases diverted to palliative and end-of-life care rather than to operating rooms or intensive care.

 

Triage is derived from a French verb: trier, to separate or distinguish. It was developed as a form of patient designation and allocation among personnel working in high-risk or high-volume emergency situations. In its earlier forms, it made essential discriminations between patients whose injuries were deemed too severe to expend resources on, those who would be best served (i.e. most likely to survive) by treatment, and those with injuries were mild enough to allow them to withstand delays in treatment. This basic process of decision-making has evolved and diversified into different forms of triage. These may prioritize patients based on available resources, injury severity (as in the section 'Considerations in Executing Mass Casualty Scenarios Effectively') wait times or patient responsiveness. Some modern forms of triage may be driven by computerized or computer-enhanced decision-making.

However, the majority of on-site triage is typically staffed and delivered by physicians or specialist nurses [2]. This may be delivered through visual assessment or more hands-on evaluation (e.g ausculation, percussion and other forms of basic assessment). It is also based on patient interview, in cases with patients capable of responding, or on the information supplied by paramedical staff. The process is most often performed in emergency department or hospital settings. This traditional form of triage is regarded as the best, as the professionals may directly assess patients and thus most accurately evaluate symptoms and diagnose symptoms.

 

An alternative form of triage is delivered by telephone. This allows an alternative form of contact with triage professionals [3]. A telephone triage respondent assesses reported signs and symptoms and issues instructions to travel (or arranges patient transport) to the appropriate facility or center [3]. For phone triage, a patient is often assessed through a system of questionnaires, which should be analyzed using clinical techniques and practice. This is the basis of patient assignment to a treatment setting. The process may be also enhanced using simple imaging techniques, most notably ultrasound [4]. This modality has many advantages (which will be discussed in more detail below) making it very amenable to triage staff and settings. It has the potential to distinguish between patients with minor internal injuries and those in need of immediate attention [4]. Ultrasound can also validate precautionary or contingency procedures carried out by paramedics, medical staff in combat and disaster situations and other first responders [4].

 

In many countries, including the UK, triage is often initiated by a single nurse. A systematic review of 25 relevant studies indicated that placing a senior physician in this role instead resulted in general improvements in emergency room performance [2]. Two randomized-controlled trials set in Canada demonstrated that the adaptation resulted in significant reductions in length of stay for patients with moderately acute conditions [2]. Two more trials suggested that this change resulted in significant reductions in wait times, while two others showed a reduction in the number of patients who left without assessment [2]. Other studies reiterated this last finding, but they were of a weaker design (i.e. pre-post studies) [2]. Systematic review also found that senior physician attendance did not affect the incidence of adverse events, patient satisfaction or cost-effectiveness [2]. The conclusivity of triage review is also affected by the lack of large-scale trials designed to adequately characterize the effects of changes to triage procedures.

 


  1. Examples of Correct and Incorrect Applications of Triage

 

It is clear that triage is often stratified in terms of immediate patient need, healthcare resources and probable life quality after treatment. Triage determines the patient's next destination, mode of treatment and how long they must wait for treatment [2]. Other factors that affect the patient experience as a result of triage are the total length of stay in an emergency setting, the probability of leaving a triage area without treatment, and that of leaving an emergency department without full treatment or resolution of their condition [2]. Adverse events as a result of triage may include mis-assignment of patients to emergency treatment when they do not need it, ('over-triage') the underestimation of symptoms leading to delayed or absent necessary treatment ('under-triage') and diversion to palliative care when the patient is likely to survive. Others include mortality, second-line treatment to address complications of emergency medical or surgical procedures, unplanned emergency department visits and physician or surgeon error.

 

There may be concerns about the safety of phone-based triage, as the staff in question obviously cannot see and examine a caller, and thus assess the next steps in care [5]. However, a recent systemic review of 13 observational studies indicated that telephone triage was safe for 97% of the patients included, although this figure decreased to 89% for patients with severely urgent causes to seek care [3]. Six studies reported the adverse events of medical error, seven mortality and five hospitalizations [3]. This study suggests that telephone triage may benefit from increased development, and from additional staff training directed at correctly identifying and assigning calls from patients with highly urgent needs. Many studies concerning the safety and efficacy of phone-based triage are based on virtual or simulated patients [3]. These result in safety rates as low as 50% for highly urgent cases [3]. Studies using real patient data indicate that approximately 10% of cases are unsafe [3]. Most of these studies focus on the probability of adverse events related to under-triage, suggesting that staff underestimate symptoms and responses to standard questions given over the phone [3]. A cross-sectional study of the telephone triage response at 17 medical centers indicated that respondents reach a decision following a minimal number of standard questions [5].

 

The majority of research conducted on the risks of phone triage tends to focus on the possibility of under-triage. However, over-triage resulting from these interactions is also possible, and is in need of further documentation and study. On the other hand, the risks of phone triage may be mitigated by standard follow-up and return consultations after first-line treatment [3]. Some studies suggest that phone triage should extend beyond the estimation of severity and need for acute care to further advice, such as the home or conservative management of relatively minor injuries or disease events [5]. In real-world situations, errors in triage may be corrected by emergency-room physicians or specialists at later stages of treatment. The probability of this is affected by factors such as the rate of patient deterioration [3]. Triage errors and failure may be avoided by additional training for staff, increased support and input from senior or more experienced physicians, and (in the case of phone triage) the increased clinical relevance of questionnaire systems and data collection.

 


Trauma Radiography: A Review


  1. Head and Brain Injuries

 

The timely assessment of head trauma as it presents in the emergency department or other center is often vital to the continued survival and life quality of the patient. These injuries are major risk factors for traumatic brain injuries (or TBIs). TBIs may be patently life-threatening, as the brain has central control over autonomic functions and consciousness. When not immediately fatal, they may still have long-term consequences such as progressive cognitive, motion and sensory deficits. This is related to the death or dysfunction of brain matter as a result of trauma. Damage to the vascular system of the brain may also exert adverse events. Some patients who have experienced impacts or other injuries to the skull may not exhibit overt symptoms that may indicate traumatic brain injury. Therefore, assessments that give a clear picture of damage to brain tissue are standard procedure. Imaging is a powerful tool in the delivery of this, detecting signs such as intracranial hemorrhages and the loss of white matter.

 

Imaging for traumatic brain injury should ideally select for brain tissue and eliminate signals from other sources, including skull and cerebrospinal fluid. Techniques used in the first-line assessment of suspected TBI include conventional computed tomography (CT) and magnetic resonance imaging (MRI). Dual-energy CT is associated with high sensitivity for hemorrhage within the brain [6]. Signs of hemorrhage on CT-generated images include hypoattenuation (which may appear to converge or be confluent) in white matter [7]. However, hemorrhage may also be indicated by points of hyperdensity on CT images [7]. Conventional CT is also associated with superior diagnostic ability for cases in which mild to moderate TBI is suspected [8]. It can deliver sectional whole-brain images, which give an appreciable first-line image of gross pathology. However, it may not be sensitive enough to damage at regional or cellular levels, including diffuse axonal injury (DAI) [9]. DAI is a prominent form of white matter damage, and increases the risk of long-term progressive loss of brain function due to undetected and untreated axonal dysfunction that may spread through brain regions [10]. This is due to cellular damage, related to factors such as the release of oxidative or otherwise stress-inducing materials from dead cells, inflammation and attack by pathological molecules such as beta-amyloid precursor protein [10]. MRI has been found to be comparable to CT in the initial assessment of TBI, with possible increased sensitivity to pathologies such as hemorrhage and brain tissue death [11]. Conventional MRI may be accompanied by analytic sequences such as fluid-attenuated inversion recovery (FLAIR). FLAIR effectively nullifies CSF, and may be sensitive to swellings in response to brain injury [12]. Susceptibility-weighted imaging (SWI) is a relatively new variant of MRI, which may deliver enhanced assessment of middle cerebral artery infarcts [13]. On the other hand, conventional CT is regarded as superior in the diagnosis of subarachnoid hemorrhages [14].

 

MRI is associated with some disadvantages, however, particularly in an emergency-case context. For example, some forms of MRI may be expensive [15]. This modality is also traditionally contraindicated in patients who present with metal artifacts, debris or implants. Modern MR hardware does not necessarily pose a danger related to mechanical damage caused by the movements of these artifacts. The presence of metal may still distort, void and clutter signals, thus negatively impacting the quality and validity of the resulting images [16]. However, some new development in sequencing can adjust to and strategically avoid or nullify metal artifacts. These adaptations include increases in bandwidth and tactical angling of the hardware and/or signal collection equipment ('view-angle tilting', or VAT) [17]. These are viable choices, although changes to bandwidth may adversely affect the signal-to-noise ratio [16]. Slice-encoding metal artifact correction (SEMAC) is a spin-echo sequence that processes each slice in a section, and encodes each phase to resolve distortion through planes [16]. SEMAC may also be referred to as 'warp' images, due to their effects on slices and of their Fourier transforms on reconstructed sections [18]. VAT may be added here to address in-plane distortion [16]. Multi-acquisition variable-resonance image combination (MAVRIC) is a similar 3D multiple-center frequency spin-echo sequence that corrects for artifacts based on resonance frequencies rather than slices [16]. These techniques may effectively reduce the effect of metal artifacts on MR-generated images, and allow for the MRI of TBI and many other injuries as described below, regardless of the presence of debris or even devices such a joint prostheses.

 

Other variants of MRI that offer sensitivity and detail in cases of suspected TBI include diffusion-weighted imaging (DWI) [7]. This technique may detect even very small areas of ischemia through changes in diffusion coefficients (or apparent diffusion coefficient (ADC)) [7]. DWI also highlights hemorrhages through increases in signal intensity [7]. Alternatives to these two main techniques may include functional imaging. This technique detects signals or emissions from tracers that can bind to biological markers of pathology. For example, positron-emission tomography (PET) can detect tracers that bind to microglia, which are activated and recruited to sites of brain trauma [19]. Single photon-emission computerized tomography (SPECT) and PET tracers may also evaluate regional detriments in cerebral blood flow, another indicator of TBI [20]. However, these options may also be restricted by considerations of resources and ease of deployment in a first-line setting. In addition, PET may require secondary analysis and even re-imaging through a second modality to correct for quantitative bias generated by attenuation. MRI may be the best technique for use in achieving this [21].

 

CT of patient with mild head trauma

Fig. 1. CT image of a patient with severe head trauma, showing isolated hemorrhages (points of hyperdensity). Case courtesy of Dr Andrew Dixon, Radiopaedia.org. From the case rID: 32393

 

 

MRI of patient with hemorrhage

Fig.2 . CT image of the same patient showing white cerebellar sign, another indicator of head trauma in which the cerebellum (within the oval) appears hyperdense compared to the cerebrum. This is often due to extensive cerebral edema (as was the case for this patient.) Case courtesy of Dr Andrew Dixon, Radiopaedia.org. From the case rID: 32393

 

 

These techniques as above often apply to closed-head injuries, or injuries associated with impacts and other forces acting on brain tissue that may not be related to skull damage resulting in deep fractures or fissures of this bone. Skull damage may also result in pain and declines in functional status. CT techniques are often indicated in the first-line assessment of these injuries [14, 22]. These clearly delineate the bone and the type of damage concerned [14]. CT may also detect other injuries or complications associated with skull fracture (e.g. hematoma) [14]. 3D CT - or 3D reconstructions of 2D images - may have high potential in the diagnosis and assessment of skull fractures [23]. Other common injuries in situations of mass casualty are dental injuries. These are also common sources of emergency care-seeking for children - some estimates claim that dental trauma occurs in over 50% of individuals in this age group [24]. A small-scale feasibility study including seven pediatric patients indicated that novel 3-Tesla (3T) MRI delivered effective distinction between nerve and other tissues and non-living material (i.e. the enamel and dentine) in sectional images of teeth [24]. This indicates potential in predicting adverse events such as necrosis within damaged teeth [24].

 

Fig. 3. Sagittal CT image (without contrast) of a skull with blunt force trauma. Arrows identify large hemorrhages.  Case courtesy of Dr Nafisa Shakir Batta, Radiopaedia.org. From the case rID: 38893

 

Fig. 4. Volumetric reconstruction of the same trauma seen in fig. 3. Case courtesy of Dr Nafisa Shakir Batta, Radiopaedia.org. From the case rID: 38893


  1. Neck Injuries

 

Patients presenting with blunt-force trauma to the head may often require additional assessment for neck trauma, and vice versa. This is often complicated by unconsciousness or agitation related to severe TBI [15]. Plain radiography is a useful first-line tool in the assessment of cervical damage (i.e. damage to the bones of the neck) [15]. Alternatively, CT, MRI or a multimodal combination of both may accurately evaluate cervical damage [15]. Skull imaging (i.e. in cases of fracture) are often extended to the top of the neck to eliminate the possibility of spinal cord damage [14]. CT is commonly indicated for this process [14]. If CT does not detect pathologies that are typically associated with the clinical signs and symptoms of the patient, follow-up MRI may be used to validate these findings [14]. Neck injuries may also be associated with significant blood loss (or the risk of this) based on the anatomical location of penetrating or lacerating injuries [25]. This risk is typically assessed through the use of CT-angiography (CTA) [25]. Alternatively, MDCT may be used to assess vascular pathology of the neck [25].

 

Other main forms of damage affecting the neck that may be seen in mass casualty settings include tracheal and esophageal damage (also known as aerodigestive pathology or injury). Damage to the bones, ligaments, tendons and muscles are also relevant to the emergency evaluation of the neck. MRI, with its often superior distinction between tissue types, is effective in the diagnosis of injuries to spinal ligaments [26]. On the other hand, some researchers argue that ligament damage and other soft-tissue injuries shown on MR-generated cervical images may be missed without specialist training in their rating [27]. Damage to the joints between cervical vertebrae is another painful form of trauma that may result in motor detriments [28]. This is often assessed using plain radiography [28]. In a comparative study of CT and X-ray imaging in vertebral joint damage, 10 cases of this were accurately detected using radiography compared to 21 using CT [28]. However, CT, MRI and multimodal imaging of the neck is associated with disadvantages similar to those affecting the assessment of head trauma.

 



Fig. 5. Non-enhanced CT showing a fracture in the first (or C1) vertebra. Case courtesy of Dr Rahmoun Fateh, href="http://radiopaedia.org/">Radiopaedia.org. From the case rID: 18698

 


  1. Chest

 

Pathologies of the chest are often highly relevant to mass casualty and emergency trauma imaging. Crushing injuries and impacts as a result of incidents such as motor traffic collisions may result in a range of pathologies, from pneumothorax to cardiac arrest. Plain radiography is often indicated in the first-line assessment of these abnormalities. These highlight injuries to the heart or lungs as characteristic changes in contrast and patent variations in morphology compared to the expected norm. Some researchers assert that cardiopulmonary ultrasound is more effective in the elimination of the possibility of congestive heart failure (CHF) in emergency situations [29]. CT (most often 2D coronal images) are also effective in showing these morphological anomalies, and are also commonly used in the diagnosis of atelectasis ('lung collapse') [30]. Damage to the vessels of the chest leading out of the heart may be assessed with ultrasound or CTA. Alternatively, conventional CT may detect vascular pathology in emergency situations [31].


  1. Abdomen

 

Abdominal trauma may encompass damage to vital organs (particularly the kidneys) and the important blood vessels (e.g. the aorta, renal arteries and mesenteric arteries). Again, these may be most effectively detected using CTA. Ultrasound and MR-angiography is also a valid tool in the assessment of interruptions and other anomalies in the flow of blood to organs in the abdomen [32]. Conventional axial CT can also demonstrate rare forms of abdominal trauma [33]. Damage to the thoracic and lumbar spine is also often assessed for in emergency situations. Injuries to these spinal regions are thought to account for up to 90% of all spinal trauma [34]. These injuries are often assessed by MRI rather than plain radiography. This should discriminate between vertebrae, nervous tissue and ligaments (the most common subjects of spinal damage) effectively. Damage to these tissues may result in chronic pain, reduction in functional status and even paralysis (due to spinal cord injury or impingement by abnormal surrounding tissue) [34]. However, the lack of reproducibility and observer agreement on the trauma types shown by these images may impact the validity of MRI as a standard in thoracolumbar imaging [34].

 


Fig. 6. The abnormalities in the first lumbar vertebra (L1/arrows in subimage B) are likely to be related to a certain type of fracture in this bone. However, the inconclusive anomaly in the nearby ligamentous complex (arrow in subimage C) leads to discrepancies in the ratings between observers. Courtesy: Lee, G.Y., et al., MRI Inter-Reader and Intra-Reader Reliabilities for Assessing Injury Morphology and Posterior Ligamentous Complex Integrity of the Spine According to the Thoracolumbar Injury Classification System and Severity Score. Korean Journal of Radiology, 2015. 16(4): p. 889-898.

 

 

 


  1. Pelvis & Hips

 

The pelvic region may be considered less complicated compared to the abdominal region, but still contains important organs, blood vessels and bones. It may be affected by a range of adverse events, including injuries, life-threatening hemorrhages, bone fractures and complications related to large tumors or other growths. The imaging of pregnancies may be considered an important facet of pelvic imaging, as the womb is mostly situated within the pelvic bone. However, the imaging of the uterus and fetus is mainly restricted to ultrasound, due to concerns related to the radioactive content of other modalities.

 

The hip joint is the articulating interface between the head of the femur and the bowl-shaped interior of the pelvis known as the acetabulum. Trauma of the hip joint often takes the form of fractures in these bony surfaces. Factors that affect the risk of these injuries include high-volume and/or high-impact activity, occupational injuries, examples of mass casualty such as motor vehicle collisions and osteoporosis (the loss of bone material resulting in detriments to bone density and integrity). This last variable is strongly associated with advanced age [35]. Hip fractures are a common cause of trauma and admissions to emergency departments for more senior adults [35]. The term 'hip fracture' may also include fractures in and very near the trochanter of the femur (or intertrochanteric fracture). This thin process of bone joins the femoral 'head' and the main shaft of the bone. All forms of hip fracture have the potential to cause significant pain and detriments to the motor ability and functional status to affected patients [36].

 

Patients affected by acute hip pain and/or damage related to osteoporosis are often referred to facilities offering hip replacements. These are procedures in which the acetabulum, femoral head or both are replaced with artificial prostheses [36]. These devices are either fixed into place using surgical cement, or coated with biomaterials or polymers that promote bone growth into the prosthesis to fix it in place [36]. Fractures of the trochanter may be addressed with screws to fix the bone together and back into its original position, if necessary. This procedure may be known as an intermedullary screw [35]. Trochanteric fractures are typically assessed using plain radiography and CT [37]. X-ray imaging is indicated as a standard in assessing cases of pain and other adverse events related to complications of hip replacement [38].

 

X-ray image of a non-cemented hip prosthesis.

Fig. 7. X-ray showing comminuted intertrochanteric fracture. Case courtesy of Dr Bruno Di Muzio, Radiopaedia.org. From the case rID: 39409

 

However, plain X-ray is regarded as inferior in sensitivity to complex trochanteric damage [37]. A prospective study of 110 patients, 104 of whom required trochanteric fixation, underwent comparative X-ray and CT assessment [37]. Plain radiography was associated with poor reproducibility and negative predictive value for complex fractures, but with 100% specificity [37]. However, CT had vastly superior negative predictive value and sensitivity ratings [37]. The CT diagnoses of fracture instability were closer to intraoperative findings (80 and 83 respectively) compared to those detected on X-ray imaging (65) [37]. This suggests that CT should replace plain radiography in cases of this trauma type, as it may be more sensitive and could improve the reproducibility of image interpretation. Another study tested this possibility, including 53 patients assessed with plain X-ray, conventional CT and 3D-reconstructed CT (3DR-CT) [39]. These images were assessed by two raters blinded to modality and using two fracture classification systems (AO and Jensen-modified Evans (EVJE)) [39]. The coefficients of reproducibility for AO were the same (0.28) for 3DR-CT and X-ray, and only marginally higher (0.33) for CT [39]. These coefficients for EVJE were similar (approximately 0.5) for 3DR-CT and X-ray, and lower (0.35) for CT [39]. This is not encouraging for examiners wishing for robust visualization of these fractures, particularly in a time-poor mass casualty situation.

 

MRI is also regarded as an effective tool in the evaluation of hip damage, hip replacement and complications related to this [17]. This is enhanced using pulse-sequencing and metal artifact reduction [17]. SEMAC may further enhance the imaging of hip prostheses, and the imaging of hip damage involving other sources of metal artifacting. A study of SEMAC and VAT in hip artifact imaging compared the addition of a SEMAC sequence to two conventional techniques (TI-weighted and short tau inversion-recovery (STIR)) to these techniques with increased bandwidth [18]. This found that signal distortion around acetabular prostheses and anatomic distinctions for both SEMAC-STIR and SEMAC-T1 were significantly improved compared to STIR and T1 with increased bandwidth [18]. Unsurprisingly, noise was also significantly reduced in response to SEMAC compared to conventional techniques alone [18]. SEMAC-STIR also appeared to be significantly more sensitive to abnormalities compared to STIR/higher bandwidth, although SEMAC-T1 was similar to T1/ higher bandwidth in these terms [18].

 

Other forms of damage in the hip region may include injuries to the tendons, muscles and soft tissues (including cartilage and synovial fluid, which surrounds and supports the bones of the joints). Muscles relevant to and/or considered to constitute the hip region may include the hamstrings, gluteal muscles and iliopsoas. These muscles also have tendons connecting the pelvic or hip bones. Injuries to these tissues may cause pain and some detriments to movement and functional status. The imaging of these structures is enhanced by MRI, as this modality offers effective discrimination between bone and tissues, and further distinction between different types of soft tissue [16]. MRI has demonstrated the ability to detect tendon injuries, and underlying pathologies such as tendon rupture and tendinopathy [40]. It may also contribute to the diagnosis of other hip-related pathologies, such as the loss of bone density and synovitis (the inflammation or irritation of synovial fluid) [40]. MRI is also indicated in the diagnosis of other forms of hip injury, including neuropathy (chronic pain or functional disorders associated with damage to nerve tissue) [41]. The sciatic nerve, a large and important branch of the peripheral nervous system running through the pelvic region to the leg, is at risk of damage as a result of hip damage [41]. This nerve is easily visualized (due to contrast changes in relation to signals from surrounding muscle) on coronal MRI sections of the hip [41].


  1. Extremities

 

Damage to the extremities often takes the form of fractures in the long bones of the arms and legs. Other risks related to mass casualty include hemorrhage from major veins, nerve damage resulting in chronic pain, motor problems or sensory deficits, and joint damage. Overt fractures are often assessed with first-line plain radiography. However, MRI or CT imaging may be necessary to detect damage to soft tissue, nerves and blood vessels. MRI is also regarded as effective in the detection of trauma to the knee joint, with high negative predictive values for damage to its important ligaments and tendons in need of corrective surgery [42].

 


Examples of Trauma Radiography in Natural Disasters & Wars

 

Evidence from studies in military and civilian defence (e.g. law enforcement and specialist teams such as SWAT) emergency medical procedures indicates that ultrasound is a powerful tool in evaluating injuries and pathologies in the field [4]. This includes first-line care and assessment in combat zones, disaster situations, events involving civil disorder and actions to resolve them. Emergency evaluation and care in the field is also known as tactical medicine or tactical emergency care [4].

 

Tactical medicine may incorporate imaging. This may take the form of well-established techniques such as ultrasound. This modality, as discussed above, is probably the most easily-deployed, and is also well-researched and well-developed in terms of education and training in its use in emergency situations. Therefore, this may make the imaging of the heart, (i.e. echocardiography) abdomen and extremities in the field more amenable [4]. Pulmonary ultrasound may validate and confirm tactical diagnostic measures such as needle thoracostomies [4]. This emergency procedure is performed to correct pressure in the thorax, usually in cases of pneumothorax with patent deterioration. It involves the insertion of a needle, usually at the level of the third rib, into the chest, outside a lung. The use of ultrasound may also prevent unnecessary thoracostomy in some situations [4]. This may also apply to emergency tracheal tube placement [4]. Ultrasound in the field can also give information on basic signs of congestive heart failure such as fluid status, and those of brain injury such as intracranial pressure [4]. It may also facilitate decisions such as optimal candidates for evacuation, and can also be used to confirm deaths in the field. This helps conserve the personnel (and resources) required for evacuation, which is a prominent concern in light of the potential dangers to them in situations such as pitched combat.

 


Considerations in Executing Mass Casualty Scenarios Effectively

 

In terms of triage, ultrasound may be deployed as a simple preliminary measure as outlined above. However, in situations of acute emergency room need as a result of an extreme event (e.g. a suicide bombing) this may be rendered unfeasible due to time constraints and large volumes of patients in need of assessment. In these cases, triage staff may need to adopt 'surrogate' indicators of trauma severity. These may include the number of injuries per patient, and the location of these injuries in sites of vital organs or vessels (e.g. head, chest or abdomen) [43]. Staff must often maintain these methods of prioritization in the face of mass panic and other psychosocial factors [43]. A study documented these measures in response to 17 suicide bombings occurring from 2001 to 2005 at a trauma center in Hadassah University Hospital, Jerusalem [43]. 164 patients were assigned to intensive care beds (52.4%) or non-intensive care (47.6%) based on the presence of skull or facial fractures, peripheral vascular trauma and injury in four or more pre-defined anatomical regions [43]. This led to over-triage in 16 (19.5%) cases. However, there was no incidence of under-triage, although 10 patients who were assigned to intensive care or directly to emergency surgery died due to uncontrollable trauma [43]. Subsequent triage from intensive care to trauma units was significantly higher than that from non-intensive care [43]. Length of stay was significantly affected by injury severity scores [43]. The authors concluded that the 'surrogate' indicators for triage in these situations were adequate, but that the use of imaging may have addressed or prevented the rate of over-triage [43].

 

CT is often the first line of imaging in cases of head trauma [14]. However, it is associated with some considerable disadvantages. CT is not amenable to portability and rapid deployment compared to other well-established techniques such as ultrasound. This modality can be brought to immobile patients in need of immediate assessment for internal injuries, but the same patients must often be brought to CT scanning facilities. This affects the decisions and resource-allocation considerations of triage and emergency staff. On the other hand, this removal to a secondary location may facilitate consultations with all of the (often numerous) different members of a multidisciplinary team involved in the delivery of care for severe trauma patients [14]. CT is also associated with the risks of radiation exposure and nephrotoxicity associated with the administration of contrast material. Radiation exposure raises concerns, particularly in pediatric cases. Nephrotoxicity is often taken into account for older patients with pre-existing kidney disease. A study assessed radiation doses in the course of CT assessment in 697 children either presenting to a pediatric trauma center (PTC) or seen at another care setting prior to transfer to a PTC. This concluded that 98% of the patients brought directly to the PTC received appropriate doses [44]. However, eight children undergoing scans at another facility were then transferred to a PTC, where they required repeat CT, thus increasing the risk of unsafe exposure [44]. The mean doses associated with other facilities was also significantly greater compared to those encountered at PTCs [44]. It must be pointed out, however, that initial CT scans in emergency situations are done without contrast, and are capable of delivering high-quality preliminary data on injuries such as skull fractures [14].

 

In terms of head trauma, it appears that MRI is more effective in assessing injuries within the brain, whereas CT is often superior in the assessment of tissue outside this organ. However, skull CT imaging may require the sedation of a trauma patient, which is a concern for some patient groups, particularly children [22]. A prospective study of ultrasound as a replacement technique in pediatric cases of skull fracture concluded that this modality has 95% specificity and 100% sensitivity compared to diagnostic CT [22]. In other words, imaging for skull injuries could be brought to the bedside in emergency settings, rather than necessitating patient transfer to a scanning site. MRI is often a viable and often comparable alternative to CT. On the other hand, it also often requires patient transfer, and may also be associated with longer scanning and processing times. This may delay diagnosis and treatment, and put additional strain on resources.

 

Historically, MRI has been associated with unsuitability in patients with metal artifacts. However, this decade alone has seen important advances in sequencing and processing that compensate for distortion caused by artifacting. The use of SEMAC adapts MRI to more patients and diagnostic possibilities. This may also assess the complications of many emergency and corrective procedures for many of the trauma types described above. For example, procedures involving hip screws may result in 'wedge-shaped' deformities of the bone, arising from the interposition of screws into the bone [35]. Screw fixation may also result in the elongation of the bone relative to the opposite trochanter [35]. A study of 46 patients (average age: 77) who had received an intermedullary screw procedure found that the corrected bones were significantly longer than that in the unaffected contralateral hip [35]. In addition, the angle of the 'neck' of the trochanter to the main body of the femur in repaired joints was significantly different compared to the 'natural' angle [35]. SEMAC-MRI may enhance the validation and monitoring of screw fixation for bone fractures for cases like this.

 

Traditionally, imaging is not associated with close correlation to clinical assessment in total hip replacements [36]. These are often the most cost-effective and successful treatments for hip damage [36]. Some procedures using cement, such as low-friction hip replacements, are associated with lengthy retention times [36]. Others, however, are associated with early prosthesis failure through migration, bone loss due to migration and with cement leakage into the joint [36]. Non-cemented prostheses are also associated with high retention rates, but also with increased costs compared to other types of joint replacement. A review of nine randomized-controlled trials comparing these two types found they were more or less comparable in terms of prosthesis success and retention [36]. However, cemented prostheses were associated with significantly reduced pain scores compared to non-cemented devices [36]. This difference was less apparent as follow-up went on, but procedures using cement were still associated with less pain [36]. It is not clear which method is superior in replacing separate joint surfaces. Some researchers assert that cemented fixation is best when fixing acetabular prostheses in place [45]. The study and practical optimization of arthroplasties like this may be enhanced by new developments such as SEMAC-MRI in the future.

 

Conclusion

 

Imaging is a demonstrably powerful aid to the diagnosis of trauma, particularly in a mass casualty setting. However, it is often less than the first step in the assessment of patients presenting with acute trauma. The process of triage often assigns the patient to a secondary setting in which imaging is performed. On the other hand, well-established modalities such as ultrasound can be deployed at this stage. This may enhance the allocation of emergency care or other healthcare resources. Ultrasound can be used to validate and confirm assessments in which internal injuries are suspected. It can even enhance contingency and/or life-saving measures such as tracheotomy. Ultrasound has been incorporated into procedures such as medical and civil defense medical support in the field to the effects as above. On the other hand, it is possible that patients should be diverted to facilities offering CT or MRI techniques when available in cases of suspected brain or skull injury. These modalities are associated with the effective imaging of gross and fine brain pathology. CT is also effective in the assessment of standalone skull trauma. MRI, in conjunction with new sequences such as SEMAC, has the potential to enhance the imaging of patients with metal artifacts and implants such as hip replacements. Plain radiography retains its well-established role in the assessment of long bone fractures. Imaging in emergency settings may have even more applications, such as the reduction of the risks linked to under-triage. 

 

 

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