American Journal of Emergency Medicine 36 (2018) 134-168

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Correspondence

Diagnostic accuracy of point-of-care ultrasound in detecting upper and lower extremity fractures: An Evidence-based approach

Fractures are among the common traumatic musculoskeletal inju- ries in emergency department (ED) patients. According to the latest Centers for Disease Control and Prevention (CDC) reports for ED visits, in 2013, fractures were consisted of more than 3.8 million visits or ap- proximately 3% of all visits [1]. Total fracture impact on healthcare and the ED as a whole will only grow as it is estimated that fractures second- ary to osteoporosis, which is a only subset of total ED fracture visits, will cost an estimated $35 billion in 2025 [2].

Traditionally, fractures and other orthopedic injuries have been commonly assessed by radiography. However, Point-of-Care Ultra- sound (POCUS) has been increasingly utilized in the ED for the diagnosis and management of these patients [3].

Ultrasound has benefits in the rapid initial detection of fractures to the upper and lower extremities. In addition, POCUS can also be used to detect associated soft tissue injuries such as ligament and tendon ruptures, which may be difficult to diagnose with plain radiographs. Therefore, POCUS may be used as a substantially advantageous modality over radiography with its lack of radiation, one-off cost, ease-of-use and its portability [4,5]. One additional benefit of POCUS is that unlike radi- ography, CT scan, and even MRI, POCUS allows for dynamic assessment of the joints and uses contralateral extremity for its comparison. POCUS has shown to be beneficial in situations where radiation limitation is im- perative such as in pediatrics, pregnancy, and patients who require seri- al radiographs for closed reduction fractures [3].

Normally, the ultrasound diagnosis of a fracture is made by identify- ing cortical disruption, subperiosteal hematomas, angulation or defor- mity, and reverberating echo [5,6]. Marshburn et al. demonstrated that after a short period of training physicians were able to rule out frac- tures with utilizing POCUS in patients older than 18 years of age with medium to low probability of fracture with a sensitivity and specificity of 92.9% and 83.3%, respectively [7].

This is further exemplified with a meta-analysis of 8 studies revealed that POCUS is consistently accurate with detection of all extremity frac- tures with a sensitivity of 83.3-100% and specificity from 73 to 100% [8]. While the evidence does not point to supplanting the use of radiographs with POCUS, it is an important supplemental tool for evaluation of frac- tures in the ED.

Upper extremity fractures often occur in the distal radius as these fractures represent up to 16% of total fractures [3]. These fractures can require serial X-rays, increasing the radiologic burden for the patient. Physicians trained with a 30-minute didactic session and 30-minute practical session were able to detect radial fractures with POCUS with a sensitivity ranging from 76 to 100% and specificity of 93-100% de- pending on the type of fractures [3]. Using POCUS, physicians looked for step-off between the intact cortex and cortex at the fracture site and then compared it to the contralateral extremity. Further

management and clinical decision was then made by looking at intra- articular involvement and degree of angulation [3].

Anteroposterior, lateral, and oblique radiographs are often required to detect and assess fractures in the elbow joint. When the radiographs are inconclusive, CT exam is often used resulting in higher levels of radi- ation exposure [5]. When evaluating for fractures via POCUS, sensitivity and specificity in elbow fracture detection was found to be 97% and 69%-88% respectively [5,9]. In the same study, POCUS had 97% and 88% sensitivity and specificity respectively, CT scans only had a sensitiv- ity of 67% and specificity of 81% in detecting elbow fractures [5]. Emer- gency physicians evaluating elbow fractures were trained for an hour with a didactic and practical lecture. In order to be identified as an

Fig. 1. Proximal ulnar fracture.

Fig. 2. Metacarpophalangeal (MCP) fracture.

0735-6757/(C) 2017

Correspondence / American Journal of Emergency Medicine 36 (2018) 134–168 135

Fig. 3. Distal fibular fracture.

elbow fractures, POCUS must identify lipohemarthrosis and elevated posterior fat pads. Boniface et al. has described an US evaluation of olec- ranon fossa for hemarthrosis and a Novel method of US guided elbow arthrocentesis [10]. Furthermore, with adjunctive History taking, areas of increased tenderness can be directly visualized and assessed [5] (Fig. 1).

Metacarpal fractures account for approximately 10% of all fractures and 40% of all hand fractures [11]. With ultrasound, two planes are visu- alized at the area of maximal tenderness. After training for 1 h it has been shown that POCUS was able to diagnose hand fractures with a sen- sitivity and specificity of 90 and 98%, respectively [11,12]. The type and

location of the metacarpal fracture was correctly identified with POCUS and the appropriate Treatment modality in relation to reduction was se- lected with a sensitivity of 96% and specificity of 100% as an angulation and step-off distance were accurately measured by POCUS [12]. Meta- carpal fractures were evaluated by POCUS and Treatment decisions were made by measuring angulation and step-off with treatment deci- sions (Fig. 2).

Multiple case reports have presented the use of POCUS to elucidate lower extremity fractures. One case series found that POCUS had the highest sensitivity in detection of femur fractures at 100% [13]. To iden- tify femur fractures, POCUS was performed in the longitudinal and transverse planes with a deep array transducer to look for any patholo- gy in the cortex via breaks, step-offs, or discontinuity. Ali et al. published a case report that diagnosed a femur fracture with only the use of histo- ry and POCUS [6]. Other case reports have found that distal fibula frac- tures were only identified through POCUS 50% of the time, as fractures in this location are subtle [13] (Fig. 3). Dallaudiere et al. has similar find- ings as their study revealed the ability to detect femur fractures as well as all lower extremity fractures with 100% accuracy [14].

Along with femur fractures, patellar fractures have been elucidated by POCUS [15]. Using ultrasound, patellar fractures can be determined by cortical disruption and associated hematoma. An added benefit of ul- trasound includes the evaluation of quadriceps tendon and patellar lig- ament and overall assessment of extensor mechanism, which may be limited by performing an exclusive clinical examination [15].

In addition to patellar and femur fractures, ankle and foot sprains are common presentations to the ED and require X-rays, which are negative 75-80% of the time [16]. By using positive Ottowa foot and ankle rules to determine the need for further evaluation, POCUS was able to detect foot and ankle fractures with 87.3% sensitivity and 96.4% specificity

Table 1

Point-of-care ultrasound in detecting upper and lower extremities fracture.

PPV: positive predictive values, NPV: negative predictive values, POCUS: Point-of-care ultrasound.

136 Correspondence / American Journal of Emergency Medicine 36 (2018) 134–168

compared to anteroposterior (AP) and lateral ankle radiographs as well as AP and oblique foot radiographs. These sonographers were trained in a combined 4-hour practical and theoretical training session [16].

Within set of all foot fractures, fifth metatarsal fracture identification with POCUS has been well documented. The vital importance of this is seen, as 5% of all fractures seen in the ED are metatarsal fractures, of which more than 50% involve the 5th metatarsal. After examining 5 test patients with fractures, ED physicians with no other formal training were able to detect 5th metatarsal fractures with a sensitivity of 97.1% and specificity of 100% by only observing for cortical disruption [17] (Table 1).

Sources of financial support

Dallaudiere B, Larbi A, Lefere M, Perozziello A, Hauger O, Pommerie F, et al. Muscu- loskeletal injuries in a resource-constrained environment: comparing diagnostic ac- curacy of on-the-spot ultrasonography and conventional radiography for bone fracture screening during the Paris-Dakar rally raid. Acta Radiol Open 2015 May 27;4:2058460115577566.

Carter K, Nesper A, Gharahbaghian L, Perera P. ultrasound detection of patellar frac- ture and evaluation of the knee extensor mechanism in the emergency department. West J Emerg Med 2016;17(6):814-6.

Atilla OD, Yesilaras M, Kilic TY, Tur FC, Reisoglu A, Sever M, et al. The accuracy of bed- side ultrasonography as a diagnostic tool for fractures in the ankle and foot. Acad Emerg Med 2014 Sep;21:1058-61.

Yesilaras M, Aksay E, Atilla AD, Sever M, Kalenderer O. The accuracy of bedside ultra- sonography as a diagnostic tool for fifth metatarsal fractures. Am J Emerg Med 2014 Feb;32:171-4.

This study was not funded.

Author disclosure statement

No competing financial interests exist.

A. Pourmand MD, MPH*

H. Shokoohi MD, MPH

R. Maracheril, BS

Atipamezole as an emergency treatment for overdose from highly concentrated alpha-2 agonists used in zoo and wildlife anesthesia

The availability of highly concentrated forms of common Anesthetic agents has revolutionized zoo and wildlife medicine [1-3]. As an exam- ple, using highly concentrated alpha-2 agonists (?2a) such as medetomidine (MED), veterinarians are able to provide safe and effec-

Emergency Medicine Department, George Washington University School of Medicine and Health Sciences, Washington, DC, United States

*Corresponding author at: Department of Emergency Medicine, George Washington University, Medical Center, 2120 L St., Washington, DC

20037, United States.

E-mail address: [email protected] (A. Pourmand).

23 June 2017

http://dx.doi.org/10.1016/j.ajem.2017.06.052

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    tive anesthesia of a 6000 kg elephant with a single 3-ml dart delivered from distances up to 50 m from the ground or by helicopter. Using these potent agents in the field, the potential for fatal accidents in humans is concerning because there is no antidote [1-4]. With highly concentrated medetomidine (HCMED), (40 mg/ml) an accidental dose of one milliliter is potentially 200 times an intravenous dose known to cause cardiac arrest in humans [5-8]. Life-threatening accidents with veterinary ?2a’s have been described in the literature [2,4].

    The current management of accidental overdose (OD) of ?2a is primar- ily supportive care [9]. While not FDA approved for use in humans, atipamezole (AT) is a selective alpha-2 antagonist, which competitively in- hibits alpha-2 adrenergic receptors [10]. AT is routinely used in animals anesthetized with ?2a for the rapid reversal of sedation and analgesia [3]. AT has been studied in both unanesthetized and dexmedetomidine (DEX) sedated humans, and has been shown to be both safe and effective [10-11]. If a dart accident occurred with HcMED in a setting where there is no available intensive care, the results would be life-threatening. For veter- inarians and institutions using these dangerous drugs, an emergency pro- tocol using AT for resuscitation of an overdose of ?2a is badly needed [2]. We performed a PubMed search from 1970 to 2017 for all informa- tion related to AT use in humans [10-15]. We then compared the exper- imental AT dosing information obtained in human subjects with its use in primates and other animals to construct an algorithm for emergent

    management of ?2a OD with AT.

    Determination of a potential human AT reversal dose for use in emer- gencies requires an estimate of how much AT would be both safe and effec- tive using the known data from the human studies. Karhuvaara et al. studied the effect of AT in unanesthetized male volunteers at doses of up to 100 mg [10]. There were minimal side effects. Scheinin et al. studied human volun- teers exposed to 2.5 mcg/kg intramuscular DEX and then given 3 different doses of IV AT, one hour later. Only the 150 mcg/kg AT (AT/DEX ratio 60:1) fully reversed the sedative and Cardiovascular effects [13].

    AT is routinely used at the end of a veterinary anesthetic on animals including primates, gorillas and chimpanzees, to reverse the ?2a for rapid recovery [3]. In Veterinary anesthesia AT is dosed on a milli- gram-to-milligram ratio relative to the amount of the ?2a used for an- esthesia. This reversal ratio is consistent in the veterinary literature, at approximately 5 times the MED dose [16-21].

    The human trial data reveal that compared to animals including pri- mates, humans require approximately 10 times less ?2a such as DEX for deep sedation, and 10 times more AT for adequate reversal. It is also known that 100 mg AT is safe even in unanesthetized humans [10]. Using this information we have a devised a simple and practical