How to Assess and Treat Acute-Onset Non–Weight-Bearing Lameness in an Ambulatory Emergency Setting

HOW TO MANAGE CRITICAL FIELD EMERGENCIES

C. Ryan Penno, DVM

1. Introduction 2. History and Physical Examination Acute-onset non–weight-bearing lameness is a com- A thorough and complete history is important in the mon emergency complaint to the ambulatory prac- examination of horses with non–weight-bearing titioner. The initial consultation commonly lameness. Factors such as age, sex, breed, and dis- contains the phrase “he was fine yesterday and to- cipline can predispose a horse to particular injuries. day cannot bear any weight on the leg,” or, “he was Historical details such as prior lameness or recent sound while being ridden and suddenly came up farriery can help further narrow the list of differen- severely lame.” The most common causes of acute tial diagnoses. Horses engaged in different disci- non–weight-bearing lameness include subsolar ab- plines may sustain discipline-specific injuries, which scessation, penetrating hoof injury, fracture, may help focus the differential diagnosis list and laminitis, severe soft tissue injury, and cellulitis.1,2 reduce time to diagnosis. It is important to observe the horse’s attitude, Diagnosis of the lameness can be difficult especially level of distress, and respiratory effort from outside if the initial cause was not witnessed. Using the the stall to ascertain the level of pain the horse is AAEP lameness scale, these emergency cases would experiencing without the added stress of a veteri- be classified as Grade 4 to 5 of 5. Grade 4 is defined nary examination. A rapid assessment of the nat- as “obvious lameness with a marked nodding, hitch- 2 ural environment of the patient including number ing, or shortened stride” and Grade 5 is defined as and character of pasture mates, quality of fencing “lameness produces minimal weight bearing in and housing, loose structural materials, and charac- motion and/or at rest or a complete inability to ter of the footing can also affect the diagnosis. 2 move.” Once a full history and visual inspection of the en- This article is intended to assist the ambulatory vironment is complete, a gross examination of the practitioner in preparation of appropriate diagnostic horse in its own environment is very useful. tools and therapeutic options for an acute-onset A brief but thorough physical exam should be non–weight-bearing lameness emergency. completed before focusing on the affected limb.

NOTES

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Orig. Op. OPERATOR: Session PROOF: PE’s: AA’s: COMMENTS ARTNO: 1st disk, 2nd beb meadel 11 3286 HOW TO MANAGE CRITICAL FIELD EMERGENCIES The patient’s posture and stance can guide the prac- should prompt the practitioner to give the distal titioner to the affected limb. A visual assessment structures a more thorough inspection. Given the of swelling, hemorrhage, or trauma should be per- prevalence of subsolar abscessation, this is a good formed. In an ambulatory setting, a horse may location to begin the examination of the limb. Ele- spend significant time outdoors and can be covered vate the limb, if possible, and remove debris from in dirt and mud. Cleaning off all dust or mud and the sole and frog, allowing a thorough exam of the removing all blanketing materials is necessary to foot for foreign bodies, penetrating wounds, or drain- complete a thorough examination. Although it age. Apply the hoof testers to all areas of the sole, may be obvious to the practitioner which limb or frog, and across the heels searching for a pain re- limbs are affected, other factors can help to deter- sponse such as an increase in muscular tension, mine severity, secondary complications, or the pos- jerking the foot away, or behavioral changes such as sibility that multiple lesions need to be addressed. attempting to bite the handler or pinning of the ears. Temperature, heart rate, and respiratory rate can Once the examination of the foot is complete, begin help determine severity, character of a lesion and moving proximally on the limb analyzing each struc- the presence of systemic disease. An increased ture in careful detail. Examine the limb thor- body temperature can also help determine if an in- oughly while the horse is weight bearing and also fectious agent, bacterial or viral, is present, whereas with the limb elevated, as lesions in deeper struc- tachycardia and tachypnea can indicate the level of tures such as the suspensory ligament may not be pain the horse is experiencing. This is particularly easily accessible without flexion of the limb. Each helpful in our more stoic patients. Mucous mem- joint should be carefully flexed and extended and branes can help determine hydration status, an im- evaluated for lateromedial motion as well. The cli- portant consideration in horses injured while nician should pay close attention to the response of working. Occasionally, the horse is in such signif- the horse as this can help guide the isolation of the icant pain that a tranquilizer or sedative must be source of pain. Some common responses indicating administered immediately, but performing a thor- local discomfort include reluctance to allow full flex- ough physical exam before sedation or tranquiliza- ion or extension and jerking the limb away from the tion is preferable. If sedation is required, use the practitioner. A noticeable reduction or unexpected minimum amount necessary to ensure proper re- increase in the range of motion indicates possible straint and safety of the patient and handler with- pathology of the joint or periarticular structures, out significantly altering the clinical picture. such as collateral ligaments, requiring closer atten- Once an overall assessment of the horse and a tion. While performing flexion and extension mo- basic physical examination is completed, examine tions, it is important to remember that multiple the affected limb or limbs. Each practitioner has ongoing conditions may be present and a positive his or her own procedure for performing a lameness test may not indicate the cause of the acute non– examination, and it should be the goal of a new weight-bearing lameness. Perform a careful evalu- practitioner to develop a system that works well for ation of the limb, noting any abnormalities such as him or her. No one method is superior, provided obvious trauma, heat, swelling, discharge, pain on that all structures are thoroughly examined and palpation, and change in the size or character of palpated and the same procedure is followed with tendons, ligaments, or muscles. Once a thorough each subsequent case, reducing the possibility of exam is complete, the practitioner should be able to missing a subtle lesion. Diagnosis becomes more narrow down the list of differentials and formulate a challenging when multiple limbs are affected, as diagnostic plan to confirm a diagnosis. with acute-onset laminitis or a front and hind limb Many diagnostic tools are available to the ambu- concurrently affected. The safety of the practitio- latory practitioner to aid in diagnosis. Radiogra- ner and handler during examination and manipula- phy remains one of the most important tools tion of limbs must remain the primary priority. available. Portable digital radiography has signif- Watching the horse move in the stall or alley, even icantly increased the accuracy and speed of diagno- for a minimal number of steps, is very important. sis with the ability to image the affected limb on site Analyzing the foot placement; engagement of the and assess the severity immediately. Radiography pastern, fetlock, and proximal joints; and amount of should be used when a bony abnormality is sus- weight being borne on the limb can help determine pected given the history of the lesion and the clinical location of pain. exam findings. Perineural analgesia is a very im- Start the examination with the most distal struc- portant diagnostic tool and can be used to locate a tures and move proximally in a methodical manner. source of lameness, especially if the clinical exam Palpate the hoof capsule and coronary band for in- findings are not conclusive, such as with subsolar creased temperature or defects, and palpate the dig- abscessation or severe soft tissue trauma at the level ital arteries at the level of the fetlock for an of the distal phalanx. However, radiography may increased or “bounding” digital pulse to determine if be required to first rule out the possibility of a bony the hoof is affected. Typically, an increased digital fracture before performing local anesthesia so that pulse indicates inflammation or pain originating excess weight is not borne on the injured limb, fur- from an area distal to the point of palpation and ther complicating the problem. Other diagnostic

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Orig. Op. OPERATOR: Session PROOF: PE’s: AA’s: COMMENTS ARTNO: 1st disk, 2nd beb meadel 11 3286 HOW TO MANAGE CRITICAL FIELD EMERGENCIES modalities that are useful to the ambulatory practi- ture,a or a medicated poultice pad.b The diaper or tioner include ultrasonography and thermography, cotton is applied to the solar surface, wrapped with which confirm or rule out diagnoses once the exam an elastic cohesive bandage material,a and coated has finished. with a protective layer such as duct tape. Another treatment option includes flushing the tract with 3. Subsolar Abscessation water and an iodine solutiond to aid in disinfection of One of the most common causes of acute-onset non– the underlying tissue. Soaking or poulticing is con- weight-bearing lameness in an ambulatory setting tinued until drainage has ceased and the patient is is subsolar abscessation.1,2 Horses affected with comfortable bearing weight on the limb. The use of subsolar abscessation will typically present with an antibiotics is controversial in the treatment of sub- increased digital pulse at the level of the fetlock and solar abscessation. Unless it is suspected that the will respond to repeated hoof tester application. infection includes deeper structures, antibiotics are Horses will occasionally respond to a small localized widely considered to delay the progression of abscess area with hoof tester application but more fre- drainage. Nonsteroidal anti-inflammatory drugs quently will be painful over a larger area of the sole. (NSAIDs) may be used to provide analgesia in a If the horse has been shod recently, particular at- distressed animal. Controlled exercise, such as tention should be paid to the nail locations in the hand-walking or limited turnout, can be beneficial sole of the hoof. Frequently, distal limb swelling to promote drainage using the weight-bearing cy- occurs starting at the level of the coronary band and cle of the horse’s gait. Tetanus prophylaxis is progressing proximally if the abscess has not com- highly recommended for any injury or infection in menced draining. In the author’s experience, some a patient with an unknown or unclear vaccination of the common causes of abscessation include pene- history. trating wounds, tight horseshoe nail placement, and previous laminar trauma such as laminitis or sub- 4. Penetrating Solar Injuries solar bruising. Once a lesion has been accurately Penetrating wounds to the solar surface of the hoof localized, the sole is pared with a hoof knife to iden- capsule are common in any farm situation. The tify a solar crack or tract of debris. Establishing most common offending foreign bodies in our prac- drainage is the most important therapeutic option tice include malpositioned horseshoe nails, construc- and can rapidly improve comfort and soundness. tion nails, screws, wire, and other metallic pieces Once a tract has been located, establish drainage from farm implements. These injuries should be with a small hook hoof knife or bone curette. Con- considered serious due to the many sensitive struc- tinue paring through the tract until the abscess tures within the hoof capsule. Common injuries in begins to drain or the tract nears the level of the our practice include puncture to the distal phalanx sensitive solar corium, at which time paring should creating a sequestrum, puncture to the deep digital be discontinued. The pared solar opening must be flexor tendon, damage to the collateral cartilages of just large enough to ensure proper drainage without the caudal heel, and penetration into synovial struc- being sealed by edematous tissue. Another option tures such as the distal interphalangeal joint, the is to notch the distal wall of the hoof to establish distal flexor tendon sheath, or the navicular bursa. drainage, thereby preserving the integrity of the Progression from puncture wound to non–weight- sole. This may be beneficial if the suspected ab- bearing lameness occurs when swelling commences scess covers a large surface area of the sole. If the due to injury, and, combined with the rigidity of the abscess drains, the resultant fluid is typically light hoof capsule, significant pressure builds within the grey to black in color and ranges from profuse wa- hoof capsule, causing severe discomfort.3 Horse tery discharge to a thick tar-like consistency and is owners or barn managers will frequently attempt to often malodorous. remove the offending object before the veterinary Treatments of choice for abscesses vary widely by visit; this must be avoided if possible because it can practitioner. The goal of any treatment is to induce then be difficult to find the site of puncture. The drainage of the abscess material and to allow the ability to radiograph the object in place can greatly surrounding structures of the foot to heal the defect. assist in developing a treatment program or in the A common therapy is to soak the foot once to twice decision to refer for further debridement. Keeping daily in an Epsom salts and warm water solution for the horse immobile to prevent further advancement 15 to 20 minutes. Care must be taken as this type of the foreign body is crucial. If the foreign body of treatment can dehydrate the hoof capsule reduc- was removed or if came out on its own, you may see ing its overall strength and predisposing the hoof to a small dark spot or hemorrhage resulting from further damage. Another option is to poultice the puncture to the solar corium. Locating a puncture foot, which promotes softening of the hoof capsule to the soft tissue of the frog can be difficult because making it more malleable to pressure. During the tissue may close over the tract, obscuring the weight bearing, the hoof capsule deforms, which pro- site of entry. motes further drainage. Common poulticing meth- If the foreign body is present upon the practitio- ods include coating a baby diaper or cotton in a ner’s arrival, radiographs are necessary to ascertain compound such as ichthammol, an Epsom salts mix- the location, vector, and structures involved. If the

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Orig. Op. OPERATOR: Session PROOF: PE’s: AA’s: COMMENTS ARTNO: 1st disk, 2nd beb meadel 11 3286 HOW TO MANAGE CRITICAL FIELD EMERGENCIES foreign body is not present, thorough cleaning and 5. Fractures disinfection of the hoof is done to identify the entry Traumatic fractures can occur in any environment. wound and then a malleable radiopaque probe or A diagnosis of fracture should be ruled out with any radiopaque contrast material can be passed into the occurrence of an acute non–weight-bearing lame- tract and radiographs taken. It is important to ness. When a fracture occurs, the bone loses its take multiple radiographic views of the foot because structural function in varying degrees depending on it may be difficult to ascertain the involved struc- the location, type, and character of the fracture. tures with only a lateral view. Once a diagnosis of Severity of lameness is dictated by the degree of loss the structures involved is made, a treatment plan of structural function and the specific bone affected. can be formulated. Fracture of the major load supporting bones typi- Once the penetration site is located, it is crucial to cally results in severe lameness.6 Fractures of the open the tract with a hoof knife or bone curette and long bones, scapula, and pelvis can occur due to remove all necrotic debris. The hoof should be con- severe trauma such as kick injury or the result of a sidered at risk to develop a subsolar abscess and fall. Fractures of the distal limb can occur due to treated accordingly as discussed in the previous sec- stress torsion, hyperextension, or hyperflexion. tion. Thorough irrigation of the tract with a teat Fractures of the distal phalanx typically occur with d cannula using sterile saline and an iodine solution heavy concussion on an uneven object, such as a rock is an effective method for disinfection. If synovial or uneven frozen ground, or can be a pathologic distension is noted in the distal interphalangeal fracture secondary to pre-existing disease. If the joint or distal flexor tendon sheath during the exam, fracture is open, the prognosis is significantly worse, a synovial fluid sample should be taken for cytology, proportional to the amount of contamination and culture, and sensitivity. The synovial structure length of time exposed to the environment. Body should be thoroughly irrigated with a sterile saline weight of the horse can also have an effect on overall solution and infused with an antibiotic such as ami- prognosis. As body weight increases, the prognosis kacin. If it is likely that the deeper structures such for full recovery decreases due to the load placed on as the deep digital flexor tendon (DDFT), distal pha- the implant or on external coaptation. lanx, or synovial structures sustained damage or A fracture of the major load supporting bones will were penetrated, referral for aggressive treatment often present with acute swelling, pain, and occa- and surgical debridement of the affected tissue sionally crepitus on palpation and manipulation of should be considered. Advanced diagnostic proce- the limb in the region of the fracture. If a fracture dures, such as MRI and CT, can be very helpful to is suspected, radiography is an invaluable tool to diagnose the amount of damage sustained. assess the character of the fracture, whether the Broad-spectrum antibiotics for 10 to 14 days, fracture is simple or compound, and the location of NSAIDs, and tetanus prophylaxis are recommended the fracture. In certain circumstances, radiogra- in treating a penetrating solar wound. After initial phy may not be essential to determine the presence treatment is complete, bandaging the foot is neces- of a fracture such as open fractures where bone sary to prevent continued contamination. A hospi- fragments are visible. These factors will dictate tal treatment plate can be applied and ensures good the type of coaptation needed. A diagnosis of frac- protection and support for the affected foot while ture in the limb that is able to be stabilized surgi- allowing easy access for continued treatment. A cally should prompt an ambulatory veterinarian to treatment that is commonly used and very effective recommend referral. Some fractures may not re- is a distal regional limb perfusion with antibiotics. quire or are unable to receive surgical intervention A tourniquet is placed just proximal to or at the level such as a pelvic fracture or depression fracture of of the fetlock; a catheter or butterfly cannula is the scapula. If surgery is not an option, long-term aseptically placed in the digital vein, and an antibi- coaptation is possible but likely to carry a guarded to otic/saline mixture is infused. The most common poor prognosis. Therefore, due to the severity of antibiotic used in our practice is amikacin. An ef- the injury, euthanasia must be considered as a hu- fective combination is using 20 mL of sterile saline mane alternative. and 500 to 1000 mg of amikacin sulfate injected into A number of resources exist for coaptation of a the digital vein with the tourniquet removed after fracture in preparation for transport to a referral 30 minutes.4 Studies have shown that 125 mg of facility and for adequate stabilization for the level of amikacin in a regional limb perfusion causes intra- injury within the limb.7,8 At minimum, a Robert synovial concentrations to reach 25 to 50 times the Jones bandage consisting of multiple layers of cotton minimum inhibitory concentration of most patho- and tension bandaging can be used to provide sup- gens.5 Few data exist to determine the amount of port to the affected limb. The overall size of the antibiotic required to reach adequate minimum in- bandage should be least 3 times the diameter of the hibitory concentrations in extrasynovial tissues limb. Apply each layer of cotton and firmly secure when performing this technique; therefore, using a with rolled gauze. With each successive layer, the higher dosage of antibiotics (the aforementioned 500 amount of tension placed on the gauze should in- to 1000 mg of amikacin) may be needed. crease to create a stable support wrap. The outer

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Orig. Op. OPERATOR: Session PROOF: PE’s: AA’s: COMMENTS ARTNO: 1st disk, 2nd beb meadel 11 3286 HOW TO MANAGE CRITICAL FIELD EMERGENCIES layer is then secured with an elastic cohesive ban- the repair by less-developed muscle/tendon units. dage materialc and nonporous adhesive tape. If the Certain types of fractures, uncommon in adult fracture is open, a thorough lavage, cleaning, and horses, are more common in foals. These include disinfection of the wound should be done with great Salter-Harris type fractures, which warrant a closer care. Aggressive cleaning and debridement could inspection of the physis and epiphysis on radio- further destabilize the fracture. Apply a wet-to-dry graphs. A similar diagnostic approach is used in bandage directly to the wound and then apply the foals as in adults to identify a fracture and develop a Robert Jones bandage to the limb. Once a Robert treatment protocol. Due to less body weight, ban- Jones bandage is secured, apply a splint of PVC or daging and splinting methods may be more success- wood in proper alignment for the level of the frac- ful in treating a simple fracture than in adult horses ture. Secure the splint in place with nonporous but referral to a surgical facility should be offered. adhesive tape overlying the entire bandage. The As in adult horses, certain types of fractures may goal of splinting is to ensure immobilization of the warrant the inclusion of euthanasia as a humane joint proximal and distal to the fracture site. If option due to a poor prognosis. possible, two splints applied at a 90° angle to each other will provide the most effective stabilization. 6. Laminitis Good references exist for splinting a fracture,8,9 and Laminitis remains one of the most common and keeping a copy in the ambulatory vehicle can be very most difficult conditions to treat in equine medicine. helpful. If the fracture is located in the distal limb, There is a vast amount of data published on lamin- a Kimsey splint can be used to align the bony col- itis and research will continue as equine practi- umn and relieve the fulcrum at fetlock and pastern tioners struggle to understand and control this de- joints. Depending on the level of distress of the bilitating disease. Laminitis can result from a patient, sedation may be needed. Care must be multitude of conditions including “grass” founder, taken to not use an excessive amount of sedative, carbohydrate overdose, endotoxemia, retained reducing the patient’s ability to maintain a solid placenta, gastrointestinal disease, respiratory dis- stance. Appropriate analgesia is crucial to main- ease, metabolic disease, and iatrogenic treatment. taining comfort of the patient and reducing stress. Laminitis can occur unilaterally, bilaterally, or in- NSAIDs and opioids such as butorphanol can be volve all four limbs. The disease can be broken used to reduce pain at appropriate dosages. If con- down into three general phases. The developmen- tamination of the fracture is suspected, broad-spec- tal phase is the time between the initial insult and trum intravenous antibiotics should be started the onset of clinical signs. The acute phase is the immediately. Once the bandage and splint are ap- time from the onset of clinical signs but before the plied, load the horse as soon as possible for trans- displacement of the distal phalanx, typically lasting portation to a referral hospital for further workup the first 72 hours. The chronic phase is the time and treatment. Horses should ideally be positioned after the displacement of the distal phalanx has straight, forward to rear, with the fractured limb occurred.9 From an ambulatory emergency per- pointing to the rear of the trailer. This allows the spective, patients requiring treatment will be in the horse to brace for the braking inertia of the trailer. acute laminitic and/or chronic active laminitic cate- When adequate fracture stabilization is not possible, gories. Clinical signs emerge after enzymatic lysis as with some proximal limb fractures, transport has occurred in the lamina of the hoof due to the should not be attempted. In these cases, an on- metabolic processes that occurred during the devel- farm supportive care program can be considered, opmental stage. Once the lamellar bonds begin to utilizing methods such as highline or cross-tie re- break down, the combination of weight-bearing straint, distal limb support, and environmental and forces on the bony column and the pull of the deep behavioral management. Euthanasia should also digital flexor tendon causes the distal phalanx to be considered a viable and humane option in frac- rotate or descend inside the hoof capsule. tures in which adequate stabilization by external Horses with laminitis typically present with se- coaptation or surgery is not possible or supportive vere discomfort on one or two limbs, most commonly care is not feasible. These fractures may include in the forelimbs. Unilateral laminitis is usually but are not limited to open contaminated fractures associated with excessive weight bearing secondary with comminution, catastrophic compound fractures to contralateral limb lameness. Clinical signs of of load-supporting bones, or severe fractures with acute laminitis include an increased digital pulse, difficult or impossible access such as acetabular increased heat of the hoof capsule, swelling or de- fractures, in which external stabilization also not an pression of the coronary band, shifting weight be- option. tween affected limbs, and a “rocked back” or Fractures in foals tend to carry a better prognosis “camped under” stance. Tachycardia, tachypnea, than in adult horses. Some of the reasons for a and pyrexia are common findings and are attribut- more favorable prognosis include lower body weight, able to significant pain. Horses with laminitis will potential for growth, ability to repair more rapidly, often be acutely sensitive to hoof tester application. the ability to restrain the foal, the ability to remain However, it may be difficult to evaluate a limb when recumbent for longer periods, and reduced strain on the contralateral limb is also involved due to the

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Orig. Op. OPERATOR: Session PROOF: PE’s: AA’s: COMMENTS ARTNO: 1st disk, 2nd beb meadel 11 3286 HOW TO MANAGE CRITICAL FIELD EMERGENCIES reluctance of the horse to bear weight. Perineural currently is beneficial with careful monitoring of analgesia can be used to improve short-term comfort secondary complications of their use. Butorphanol or for performing minor procedures but is not always administered episodically or diluted in a polyionic successful in extreme pain situations. If perineural solution as a constant rate infusion provides effec- analgesia is needed for application of therapeutic tive analgesia. Combining butorphanol with seda- implements, the horse should be reevaluated once tive compounds such as xylazine or detomidine, the analgesia has worn off. Radiography of the dis- which also have analgesic effects, can be very effec- tal phalanges of horses with laminitis is desirable, tive if the patient is in distress. While little sup- especially when rotation or distal displacement is porting scientific evidence exists, dimethylsulfoxide suspected. A minimum of a lateromedial view and (DMSO) administered intravenously is widely used a horizontal dorsopalmar/plantar view are needed to by veterinarians as an anti-inflammatory by way of assess the degree of rotation and/or descent of the scavenging free radicals. DMSO is diluted in poly- distal phalanx. The lateromedial view alone can- ionic saline solutions and administered as a con- not assess the amount of medial or lateral asymmet- stant rate infusion. Acepromazine can have a ric descent of the distal phalanx. Once radiographs beneficial effect by providing peripheral vasodila- are taken, measurements can be used to determine tion. While treating the effects of laminitis, it is the degree of rotation, the solar thickness at the important to treat the primary causative condition. apex of the distal phalanx, the amount of descent of Antibiotic treatment, anti-endotoxic therapy, and the coffin bone, and the separation of the lamina intravenous fluids should be considered as adjunc- from the hoof capsule. Even if no radiographic tive treatment if the ongoing laminitis is secondary changes have taken place, this baseline set of radio- to an identifiable primary insult. The horse owner graphs can prove invaluable later in the course of should be made aware of the potential treatment treatment. options once the horse progresses to the chronic Treatment of acute or chronic active laminitis is phase of laminitis such as corrective shoeing, anal- highly variable and dependent on the client, patient, gesics, and rehabilitation programs. and attending practitioner. The goal of treatment is to reduce the discomfort of the horse and to aid in 7. Severe Soft Tissue Injury stabilization of the distal phalanx within the hoof Severe injury to the soft tissue supporting struc- capsule either during descent or immediately after tures of the limb can cause significant lameness, termination of the acute phase. In the author’s particularly in the pre-acute stages. Horses will practice, cryotherapy is very beneficial in reducing typically present with tachycardia, tachypnea, and discomfort of horses with laminitis. It is important pyrexia consistent with significant pain. Injuries to apply the cryotherapy from the metacarpal bones to the suspensory ligament, flexor tendons, collat- to the distal phalanx. This will aid in cooling the eral ligaments, and major muscle groups may all blood flow before arrival at the distal limb. Con- present initially with acute non–weight-bearing stant cryotherapy in the form of ice boots has shown lameness. This type of injury may not present with to be more beneficial than episodic treatment.10 significant swelling in early stages and can initially It is important to treat as frequently as possible be a diagnosis of exclusion. The environment can when using episodic cryotherapy. The patient play a role in the diagnosis of the injury. In condi- should be housed in a stall or confined area with tions of deep mud, snow, or ice, soft tissue injuries to deep, soft bedding such as shavings or sand. Solar muscle groups and periarticular structures are more hoof support can help support the bony column and common. Injuries incurred in performance disci- distribute the weight of the horse over a larger sur- plines such as jumping, barrel racing, or endurance face area thereby reducing focal pressure on the should prompt close examination of the flexor ten- central toe region of the sole. Using Styrofoam, dons, suspensory ligaments, and periarticular struc- closed cell foam material, frog support pads, or mal- tures. In the absence of significant swelling or leable impression material formed to the frog and heat, it is crucial to rule out other causes of severe sulci can provide effective support. When using lameness such as fracture or pathology of the hoof. moldable materials, it is important to remember If significant swelling and pain are present, ruling that they can be easily compressed and should be out bony fracture is also important. Careful palpa- changed frequently. The initial compressed por- tion and manipulation of the involved structures is tion that has molded to the structure of the sole can critical to diagnosing a soft tissue lesion. Muscle be reused and fresh material applied in combina- injuries are typically painful on direct palpation and tion. The support material of choice is held in place extension or flexion of the limb. In performance with an elastic cohesive bandage materialc or duct situations, exertional rhabdomyolysis must be con- tape wrapped around the hoof and heel bulbs, taking sidered. Horses with a muscle condition often will care not to compress the coronary band. be painful over the psoas and gluteal muscle groups. Systemic analgesia with NSAIDs such as phenyl- Supporting soft tissue structures such as the super- butazone, flunixin meglumine, ketoprofen, or firo- ficial and deep digital flexor tendons and suspensory coxib should be administered immediately. Use of ligament are likely to be painful on direct palpation NSAIDs such as phenylbutazone and flunixin con- and tend to form localized swelling. Injuries to the

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Orig. Op. OPERATOR: Session PROOF: PE’s: AA’s: COMMENTS ARTNO: 1st disk, 2nd beb meadel 11 3286 HOW TO MANAGE CRITICAL FIELD EMERGENCIES periarticular structures may present with signifi- inflammation, swelling, and pain. Placing a firm cant joint effusion and pain elicited on joint stress wrap of cotton padding, rolled gauze, and an elastic manipulation. Radiography of the affected limb cohesive bandage materialc is important to provide should be considered to rule out bony lesions such as support to the limb and limit ongoing swelling and fracture. If the instrumentation is readily avail- edema. If the injury has occurred to the proximal able, a complete blood cell count can be helpful in region of the limb, a stacked bandage or Robert ruling out differential diagnoses such as cellulitis Jones bandage may be necessary. It is important or intra-articular sepsis. Serum chemistry panels to replace or reset the bandage once to twice daily to containing muscle-specific enzymes such as creatine limit secondary pressure injury. In addition to pro- kinase, lactase hydrogenase (LDH), and aspartate viding support to control swelling and edema, cer- aminotransferase (AST) can help determine the tain severe soft tissue injuries require bandaging for extent of muscle damage and aid in the diagnosis stabilization purposes. These include flexor tendon of rhabdomyolysis. Urinalysis can also be very use- ruptures and collateral ligament ruptures. The ful in determining if muscle damage has occurred, placement of a firm support wrap is indicated in as the urine will typically be discolored from red to these instances; a splint in the appropriate location brown. may be necessary to achieve adequate stabilization. For soft tissue lesions, ultrasonography is one of If referral to a hospital is indicated, further support the most important diagnostic tools available to the such as a Robert Jones bandage and a splint should ambulatory practitioner. Diagnosis of a significant be considered to limit damage during transporta- lesion in structures such as the suspensory ligament tion. Topical products, such as DMSO and nitro- or collateral ligaments can alter treatment in the furazone, alcohol, or commercially available poultice acute stages. Once the lameness has been localized products have been used successfully to reduce in- to a region of the limb, targeted ultrasonography can flammation and edema. Care must be taken to help determine the structures involved, the extent to avoid a dermatological reaction in an already com- which the tissues have been damaged, and the treat- promised tissue and to avoid further exacerbating ment plan required. the pain and irritation of the horse. Treatment of severe soft tissue lesions varies, depending on the diagnosis. Strict stall rest should 8. Cellulitis be instituted to limit further damage to the affected structures until a detailed treatment plan has been Cellulitis is a difficult and frustrating condition to made. If severe muscle damage is present due to a diagnose and treat. In the practice region of the pre-existing muscle condition or trauma, intrave- author, cellulitis occurs rapidly, with little warning, nous fluid therapy with balanced electrolyte solu- and frequently results in partial to full limb swell- tions is important to prevent renal damage from ing, increased heat, significant pain on palpation, circulating myoglobin. If intravenous therapy is and variability in the grade of lameness from sound not readily available, oral rehydration should be at a walk to non–weight-bearing lameness. The instituted. Rehydration is important before ad- hind limb tends to be more frequently affected than ministering NSAIDs due to the possibility of renal the forelimb, and the condition tends to be unilat- 11 damage. In the absence of laboratory values such eral. The prevalence of hind limb cellulitis over as packed cell volume, total protein, or urinalysis, forelimb cellulitis is not fully understood but could fluid therapy can be estimated based on findings of a relate to the higher likelihood of trauma from kick- thorough physical exam including capillary refill ing or less frequent care due to safety concerns. time, skin tent assessment, and urine production. Cellulitis of the limb can be initiated by many fac- Electrolytes may be added to replace losses or cor- tors including puncture trauma, blunt trauma, or rect metabolic alkalosis or acidosis but should be skin barrier disruption but is commonly idiopathic. used only after serum chemistry has been The most common infectious agents isolated from performed. cellulitis cases are Staphylococcus sp. and Strepto- Once hydration status has been assessed and fluid coccus sp.11,12 These infectious agents are normal therapy instituted if necessary, pain control should dermal flora of the horse thereby leading to the be administered. NSAIDs are typically used ini- prevalence of their isolation. Other pathogens tially for controlling inflammation and pain. If the such as Escherichia coli have been found, and poly- patient continues to show severe distress or pain, microbial infections are not uncommon.12 As with administration of sedatives such as detomidine and severe soft tissue injuries, other causes of significant xylazine combined with butorphanol may be indi- swelling, pain, and lameness should be ruled out cated. Corticosteroids can be a very effective anti- before a diagnosis of cellulitis is made. Intra-artic- inflammatory therapy when indicated. Muscle ular or intrasynovial infections should not be over- relaxants such as methocarbamol intravenously or looked, but frequently these structures are obscured orally can significantly reduce muscle spasm and by periarticular swelling and distension. A thor- provide rapid comfort for the patient. For lesions of ough history must be documented, especially if the upper and lower limb, frequent use of cryother- intra-articular therapeutic products have been ad- apy can be a very useful tool in controlling ongoing ministered in the recent past.

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Orig. Op. OPERATOR: Session PROOF: PE’s: AA’s: COMMENTS ARTNO: 1st disk, 2nd beb meadel 11 3286 HOW TO MANAGE CRITICAL FIELD EMERGENCIES Clinical signs of cellulitis include pyrexia, tachy- inflammatory effects and free radical scavenging. cardia, tachypnea, significant heat, swelling, and As in other instances, if distress is present due to pain. Due to the anatomical location of major blood pain or inability to bear weight, sedation can be and lymphatic vessels, swelling and pain is usually given on an as needed basis. Butorphanol can be more pronounced on the medial aspect of the limb. administered either alone or in combination with a If available, a complete blood cell count is very use- sedative to provide additional analgesia. Frequent ful in determining the systemic impact of infection. cryotherapy in the form of cold-water hosing or ice Typically, leukocytosis and neutrophilia are seen packing can provide immediate relief to the patient along with an increased fibrinogen. Ultrasonography and aid in the reduction of swelling. Cooling the of the limb can be helpful if a traumatic lesion is found. entire limb proximal to distal is ideal. Topical If the lesion can be adequately visualized, drainage products to reduce inflammation may be used but and treatment of the infected region can decrease the can occasionally cause additional irritation and in- progression of the condition. A culture and sensitiv- flammation and thus should be chosen carefully. ity of the infected site should be obtained if possible. DMSO, nitrofurazone, and menthol-based products all Ultrasonography can be of little assistance in the ab- may be useful but may lead to additional dermatolog- sence of a gross visible lesion, as the inciting cause of ical reaction. Clay poultices, especially on the distal the swelling may be very small in a large, swollen limb limb, are effective at drawing heat without the likeli- and therefore very difficult to find and treat accord- hood of irritation. Support bandaging can limit addi- ingly. Another diagnostic option occasionally used is tional swelling, thereby reducing discomfort, and thermography. should be applied with firm tension but not overly If a traumatic lesion is present, the wound should tight. If traumatic wounds exist, they should be ban- be treated aggressively. Debridement of damaged daged accordingly. Applying a wet-to-dry bandage or necrotic tissue and frequent irrigation with an can aid in drawing exudate from infected wounds antiseptic solution, such as a diluted iodine solu- away from the surrounding tissue. A support wrap tion,d is indicated. Arthrocentesis for culture and can then be applied over the wound bandage. sensitivity is indicated if intra-articular or intrasy- Once the patient is able to bear weight, inducing novial sepsis is suspected. Case selection is critical motion through the use of controlled exercise can when deciding if arthrocentesis is appropriate due to greatly aid in the dispersal of dependent fluid from the risks of introducing infectious agents into a ster- the lower limb and reduce the severity of lameness. ile synovial structure. After arthrocentesis is per- In the lower limb, the mechanical motion of the formed, a thorough lavage with a sterile saline joints combined with the stretch and release of the solution and administration of a suitable antimicro- muscle-tendon unit will apply pressure to the vas- bial product is necessary. cular and lymphatic system circulating the fluid Systemic antimicrobial therapy should be com- proximally into the central circulatory system. menced as quickly as possible if cellulitis is sus- The owner should be made aware of the potential of pected. Broad-spectrum treatment with two or contralateral limb laminitis as a possible conse- more antibiotics is recommended until a culture and quence of the excessive weight bearing. Frequent sensitivity is received or if initiating cause is un- cryotherapy, use of anti-inflammatories, and appro- known and a culture is unavailable.12 Common an- priate exercise can reduce the incidence of laminitis. timicrobials used include potassium penicillin, gentamicin, oxytetracycline, ceftiofur, enrofloxacin, 9. Conclusion and metronidazole. Regional limb perfusion is a Acute-onset non–weight-bearing lameness is and very effective method to introduce high concentra- will continue to be one of the most common emer- tions of antimicrobials to the intravascular and ex- gencies faced by the ambulatory practitioner. The travascular structures of the distal limb.13 This is key to approaching horses in this condition is to be a technique that is relatively easy for the ambula- well prepared with the basic equipment and ever- tory practitioner to perform. This method should evolving knowledge to provide clients and patients be considered if adequate visualization of a superfi- with the best possible care. The basic principles of cial vein is possible. Ultrasound guidance can be patient care should apply to all emergency lameness helpful in locating a suitable site at which to per- scenarios including taking a thorough and complete form this procedure. If adequate visualization of a history, performing a complete physical exam, not site is not possible, as in severe full limb swelling solely examining the affected limb but the entire and tissue distension, this procedure should not be patient, creating a differential diagnosis list, using attempted due to potential complications of intro- the diagnostic tools available to you to form a diag- ducing infectious agents to synovial structures if the nosis, starting the appropriate treatment, develop- vascular system is missed. ing and implementing a treatment protocol going NSAID therapy is indicated to provide analgesia forward, and referring when necessary. and to control inflammation. If the patient is nor- mothermic, corticosteroids can be used to reduce References and Footnotes inflammation and resulting edema. Intravascular 1. Dyson SJ. Assessment of acute-onset, severe lameness. administration of DMSO has been used for anti- In: Ross MW, Dyson SJ, editors. Diagnosis and Man-

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agement of Lameness in the Horse. 1st edition. St. Louis: 8. Bramlage LR. Current concepts of emergency ﬁrst aid treat- Saunders Elsevier; 2003:145–149. ment and transportation of equine fracture patients. Com- 2. Stashak TS. Examination for Lameness. In: Stashak TS, pend Contin Educ Pract Vet 1983;5:S564–S574. editor. Adams’ Lameness in Horses. 5th edition. Balti- 9. Parks AH, Mair TS. Laminitis: a call for uniﬁed terminol- more: Lippincott Williams & Wilkins; 2002:113–183. ogy. Equine Vet Educ 2009;21:102–106. 3. Redding RW. An in-depth look at puncture wounds to the 10. Pollitt CC, van Eps AW. Prolonged, continuous distal limb foot, in Proceedings. Am Assoc Equine Pract 2010;56:512– cryotherapy in the horse. Equine Vet J 2004;36:216–220. 521. 11. Fjordbakk CT, Arroyo LG, Hewson J. Retrospective study of 4. Palmer SE, Hogan PM. How to perform regional limb per- the clinical features of limb cellulitis in 63 horses. Vet Rec 2008;162:233–236. fusion in the standing horse, in Proceedings. Am Assoc 12. Adam EN, Southwood LL. Primary and secondary limb Equine Pract 1998;44:124–127. cellulitis in horses: 44 cases (2000–2006). J Am Vet Med 5. Murphey ED, Santschi EM, Papich MG. Local antibiotic Assoc 2007;231:1696–1703. perfusion of the distal limb of horses, in Proceedings. Am 13. Rubio-Martinez LM, Cruz AM. Antimicrobial regional limb Assoc Equine Pract 1994;40:141–142. perfusion in horses. J Am Vet Med Assoc 2006;228:706–712. 6. Baxter GM, Turner AS. Diseases of bone and related structures. In: Stashak TS, editor. Adams’ Lameness in Horses. aMagnaPaste™, Butler Schein Animal Health, Dublin, OH th 5 edition. Baltimore: Lippincott Williams & Wilkins; 2002: 43017–7545. 401–457. bAnimalintex®, Robinson Animal Healthcare Ltd., Carlton in 7. Walmsley JP. Initial fracture management before transport Lindrick, Worksop, UK S81 9LB. to a referral centre, in Proceedings. Br Equine Vet Assoc cVetrap™, 3M™, St. Paul, MN 55144–1000. Conf 2008;47:220–221. dBetadine®, Purdue Products L.P., Stamford, CT 06901–3431.

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