Soft Tissue Infection 01-20, 24 Flashcards

Question

A 34-year-old woman undergoes laser-assisted liposuction of the abdomen, hips, and inner and outer thighs using a tumescent technique. A total of 2500 mL of aspirate is removed. Postoperative recovery is uneventful, and the patient is discharged home the same day. She comes to the emergency department 4 days later with intense pain over the lower abdomen and flanks. Temperature is 101°F (38.3°C). Physical examination shows the skin has well-demarcated erythema, induration, and bullae forming at multiple sites. Her incisions are seeping clear, grey fluid. Which of the following is the most appropriate management? A) Exploratory laparotomy for presumed bowel perforation B) Intravenous administration of antibiotics and local burn care C) Intravenous administration of antibiotics only D) Oral administration of antibiotics E) Surgical debridement of the involved tissue

Answer 1

The correct response is Option E. Necrotizing fasciitis is a rapidly progressive soft-tissue infection characterized by necrosis of the fascia and subcutaneous fat with subsequent necrosis of the overlying skin. Although complication rates associated with liposuction are not unduly increased, infection is a major concern, and cases of prolonged inflammation, septic shock, and infections have been documented. Likewise, cases of necrotizing fasciitis following liposuction have been reported on several occasions and, according to data reported in the literature, the overall incidence of necrotizing fasciitis is equal to 0.4 per 100,000 patients. There are two common forms that are reported: infections caused by Streptococcus pyogenes and mixed infections caused by a variety of microbes, including Escherichia coli, Proteus, Serratia, and Staphylococcus aureus. A detailed case of necrotizing fasciitis sustained by Mycobacterium chelonae after a combined procedure of liposuction and lipofilling has also been described. The progressive necrosis of the tissues typically involves the superficial fascia and the subcutaneous layer, but is limited in extension to the skin; the extent of the gangrene at the fascial layer is usually more severe and greater than at the skin level. Necrotizing fasciitis is virtually unnoticeable in the first 48 hours with nonspecific symptoms. In the days that follow, an extensive, hardened region forms, which is often dark in the center. Severe pain and necrosis follow at the level of the infection. Drainage of “dishwater fluid” is often pathognomonic. Metabolic changes occur, ending with respiratory distress, oliguria, acidosis, increased troponin concentrations, and sepsis. Diagnosis and treatment consist of surgical exploration and debridement that reveal necrotic, edematous, subcutaneous fat. Bacteriologic analysis of exudate, cultures, and histologic evaluation complete the diagnosis. Early diagnosis is imperative to avoid a fatal outcome. Treatment is based on immediate and aggressive surgical debridement with combined antibiotic therapy. Because necrotizing fasciitis is a progressive, rapid infection, the wound typically is left open for a planned “second-look” operation and additional debridement if necessary. The mortality rates are increased and range up to 70% but decrease to 4.2% after immediate surgical intervention. Delay in debridement increases mortality.

Answer 2

The correct response is Option E. Hidradenitis is a chronic and often disabling skin condition of the apocrine glands. It results in abscesses, inflammatory nodules, and draining sinuses in the axillae, groin, perineum, and occasionally the submammary area. It affects approximately 1 in 300 people, and it is more common in women, people who smoke, and people who are overweight. The axillae are more commonly involved in women, and the perineum more commonly in men. Early treatment centers around local wound care, oral antibiotics, corticosteroid injections, hygiene, weight loss, and smoking cessation. Decreased estrogen levels may also contribute, and disease often subsides with oral contraceptives and during pregnancy. Unresponsive or extensive disease requires surgical intervention for long-term resolution. Relapse rates are high, and healing is often slow. Although limited excision and closure of solitary lesions is an effective short-term treatment, new lesions are likely to develop. Fistulotomy alone has an unacceptably high recurrence rate. A long-term resolution in this severely affected patient requires complete excision of the hair-bearing skin of the affected area. The large defect created needs broad skin coverage. The best options include split-thickness skin grafting or grafting with negative pressure wound therapy immobilization. Negative pressure wound therapy followed by healing by secondary intention or coverage with local flaps are additional options, though scar contractures and shoulder stiffness are risks. Laser treatments are too superficial to treat the deeper apocrine structures. Lymphadenectomy is not necessary for a cure.

Answer 3

The correct response is Option B. Vibrio vulnificus is a common Vibrio species causing soft-tissue infections of the hand. Vibrio species are ubiquitous in aquatic environments including saltwater bodies. Immunocompromised hosts are at greater risk for amputation and death. The best chance for patient survival includes early diagnosis and initiation of appropriate antibiotics, as well as urgent surgical debridement for any evidence of necrotizing infection. A broad range of antibiotics are effective against Vibrio species, including V. vulnificus. Agents effective against gram-negative rods, including quinolones, aminoglycosides, and aminopenicillins, are all effective against V. vulnificus. While all cephalosporins are effective against Vibrio species, third-generation cephalosporins are up to 130 times more potent than first- or second-generation cephalosporins. Vancomycin, nafcillin, and linezolid are all narrow-spectrum antibiotics, primarily effective against gram-positive cocci, and are not effective against Vibrio species.

Answer 4

The correct response is Option B. Rhinocerebral mucormycosis is a rare opportunistic infection of the sinuses, nasal passages, oral cavity, and brain caused by saprophytic fungi. The infection can rapidly result in death. Rhinocerebral mucormycosis commonly affects individuals with diabetes and those in immunocompromised states. The diagnosis of mucormycosis is established by obtaining a biopsy specimen of the involved tissue, and frozen tissue samples should be immediately evaluated for signs of infection. Microscopic characterization of non-septate hyphae, rhizoids, columellae, sporangia, and sporangiospores helps to define genus and species within the order Mucorales. Optimal therapy requires a multidisciplinary approach that relies on prompt institution of appropriate antifungal therapy with amphotericin B (AmB), reversal of underlying predisposing conditions, and, where possible, surgical debridement of devitalized tissue. Surgery should be considered early, and if possible, emergently with the goal of removing all necrotic tissue. Repeated debridements are frequently necessary and the extent of surgery should ideally be guided by evaluation of frozen tissue sections examined histologically. In the scenario provided, orbital involvement will most likely require sacrifice of the eye.

Answer 5

The correct response is Option E. Staphylococcus is still the most common organism in hand infections. The most common in felons is Staphylococcus aureus. Methicillin-resistant Staphylococcus aureus community-acquired (MRSA-CA) infections are now the most predominant strain in hand infections, comprising 60% of Staphylococcus aureus infections. Pasteurella multocida should be considered with most animal bites, although it is most common with cat bites. Eikenella corrodensis associated with human bites. There is no history of bites in this case. Listeria monocytogenes has been reported in flexor tenosynovitis in immunocompromised patients. Candida albicans is usually associated with chronic paronychia.

Answer 6

The correct response is Option B. Aeromonas hydrophila is an organism present in the leech species Hirudo medicinalis gastrointestinal tract that can lead to an infection if used medicinally. In this patient with venous congestion and application of leeches, antibiotic prophylaxis is recommended with fluoroquinolones, tetracycline, or trimethoprim-sulfamethoxazole. Actinobacillus lignieresii is seen in horse bites, Pasteurella canis in dog bites, and Eikenella corrodens in human bites. In a recent review of ear reattachment methods, a variety of approaches have been used including microsurgical reattachment, burying of the part in a subcutaneous pocket, periauricular tissue flaps for coverage of the part, and direct reattachment as a composite graft. Microsurgical replantation is associated with the best aesthetic outcome even if venous anastomosis is not possible and leeching is necessary.

Answer 7

The correct response is Option D. The most appropriate next step in management is to surgically explore the wound in the operating room. The clinical picture is of a severe, rapidly progressing infection, possibly necrotizing fasciitis. A high index of suspicion and early treatment are vital for successful outcomes. Necrotizing fasciitis is a rare and rapidly progressive infection of the deeper layers of skin and subcutaneous tissues, easily spreading across the superficial fascial plane, with subsequent death of the overlying skin and severe systemic toxicity. Liposuction is the most frequently associated cosmetic surgery with this infection. Signs and symptoms are insidious, nonspecific, or virtually unnoticeable early in the course of the disease. Later, erythema, prominent edema, and induration appear, accompanied by intense or intolerable pain. The clinical picture evolves into systemic toxicity and eventually multiple organ failure. Risk factors for necrotizing fasciitis include diabetes mellitus, immunosuppression, age older than 50 years, malnutrition, and peripheral vascular disease. There are two forms of the disease: one caused by Streptococcus pyogenes, and the other by mixed infections caused by a variety of microbes, including Escherichia coli, Proteus, Serratia, and Staphylococcus aureus. The progressive necrosis of the tissues typically involves the superficial fascia and the subcutaneous layer. The extent of the gangrene at the fascial layer is typically more severe and greater than at the skin level. This insidious infection is virtually unnoticeable and nonspecific in the first 24 to 48 hours; however, in the following days, an extensive, hardened area appears, which is often dark colored in the center. Intense pain and skin necrosis follow at the level of the infection. Metabolic changes occur, ending with respiratory distress, oliguria, acidosis, increased creatine kinase activity, increased troponin concentrations, and toxic syndrome. Diagnosis and treatment consists of surgical exploration and debridement that reveal necrotic, edematous subcutaneous fat. Bacteriologic analysis of exudate, cultures, and histologic evaluation complete the diagnosis. Early diagnosis is imperative to avoid a fatal outcome. Because necrotizing fasciitis is a progressive, rapid infection, a staged “second-look” operation and, if necessary, additional debridement should be performed. The mortality rates are high and range from 20 to 70%, but decrease to 4.2% after immediate surgical intervention. Though antibiotic therapy is an integral part of the treatment, surgical exploration is key. CT scans and ultrasonography will not change the treatment plan and are therefore not the appropriate next step in management.

Answer 8

The correct response is Option C. The patient described has a web space (collar-button) abscess. Pus resides dorsal to and volar to the natatory fibers of the palmar fascia with a small connection between the two spaces passing through the natatory fibers. It is drained through proximal dorsal and volar incisions in the web space. One should not incise through the apex of the web space, as this may lead to a web space contracture. Incisions are allowed to heal by secondary intention. Cleland ligament is a separate portion of the palmar fascia located within the finger dorsal to the neurovascular bundle. It is distal to the purulence in a web space abscess. Absence of pain with axial loading of the digits makes a joint space infection unlikely, so drainage of the metacarpophalangeal joint is unnecessary. Some approaches to drainage of flexor tenosynovitis involve release of the proximal sheath through the A1 pulley; the appearance in the photo (lack of fusiform swelling), and absence of pain with passive extension of the fingers, make flexor tenosynovitis unlikely in this patient. Infection of the mid-palmar space would produce more proximal pain and swelling in the palm, which is not present in this patient.

Answer 9

The correct response is Option C. Given the patient’s history of diabetes and necrotizing non-purulent infection after minimal trauma, he is likely to have mucormycosis, a life-threatening fungal infection caused by organisms from the class Zygomycetes. On microscopy, tissue samples from patients with mucormycosis demonstrate right-angle nonseptate branching hyphae. Grape-like clusters of gram-positive bacteria is not appropriate. This option describes the characteristic appearance of a staphylococcal infection. Given the patient’s lack of cellulitis or purulent infection, it is an unlikely mechanism for this necrotizing ulceration. Septate nonbranching hyphae and yeast forms is not appropriate. This option describes the characteristic appearance of a candidal infection. Given the patient’s lack of marked erythema and excoriation, and location of the infection on the face, rather than in skin folds, the likelihood of Candida as the primary pathogen is extremely low. Chain-like collections of gram-positive bacteria is not appropriate. This option describes the characteristic appearance of a streptococcal infection. Although streptococcal infections are common in the head and neck region, the patient’s history and appearance of the lesion do not support Streptococcus as the causative organism. Tiny yeast forms with occasional unequal bud formation is not appropriate. This option describes the characteristic appearance of Histoplasma capsulatum, an opportunistic fungus, which may cause marked pulmonary infections in immunocompromised patients. Often emergent debridement is required, and that decision will need to be made on Gram stain, not on final culture.

Answer 10

The correct response is Option A. A prospective, randomized study has shown that antibiotic prophylaxis is superior to placebo in decreasing infections after human bites that are less than 24 hours old. The most common pathogens in human bite wounds are S aureus, E corrodens, H influenzae, and beta lactamase-producing anaerobic bacteria. Eikenella species are resistant to clindamycin. Meanwhile, doxycycline and trimethoprim-sulfamethoxazole are not effective against anaerobes. Of the options mentioned, only amoxicillin-clavulanate has good activity against all common oral pathogens.

Answer 11

The correct response is Option B. The most appropriate next step in management is to initiate intravenous dexrazoxane. Recent data support the use of this agent in extravasation of anthracyclines (e.g., doxorubicin) as an antidote. It has been shown to decrease the frequency and severity of tissue injury. The mechanism by which dexrazoxane diminishes tissue damage is unknown. However, two mechanisms of action are hypothesized: 1) reduction of oxidative stress due to complexes of metal ions and anthracyclines by chelating metal ions; 2) and blockade of topoisomerase II poisons by catalytic inhibition of topoisomerase II. Patients receive treatment with dexrazoxane 1000 mg/m2 administered intravenously on days 1 and 2, and 500 mg/m2 on day 3. The infusion is given in the opposite arm of the extravasation site and is administered as soon as possible and no longer than 6 hours after the extravasation accident. Flushing the port is not indicated because the port may be malfunctioning and this action could extravasate the flushing agent. Adding more fluid to the area (extravasation of saline from the port, subcutaneous saline injection, etc.) will only add to the pressure on the overlying skin, injuring the skin further. Removal of the port is not indicated until it has been ascertained it is malfunctioning. Dimethyl sulfoxide (DMSO) is a known treatment option for anthracycline extravasations. However, it is used as a topical agent with or without cortisone, not as a subcutaneous injection. Additionally, it should not be used in patients who are receiving dexrazoxane because it has been shown to decrease the efficacy of the dexrazoxane therapy.

Answer 12

The correct response is Option B. The patient described has an occupation that exposes him to contaminated water and raw seafood. Infections from Mycobacterium marinum and Vibrio vulnificus are both possible. Mycobacterium marinum is the most common atypical mycobacterium seen in hand infections, often seen after penetration by aquatic equipment, colonized marine life, or contact with contaminated water. The most common deep infection is flexor tenosynovitis, and may present as a chronic tenosynovitis. Sporothrix schenckii is a fungus found in plants and soil. Inoculation with the pathogen results in a papule at the entry site, followed by development of lesions along the lymphatic chain. Suppurative flexor tenosynovitis typically presents with pain over the tendon sheath, semiflexed position of the involved digit, pain on passive extension, and symmetrical swelling of the finger. This classic presentation is commonly caused by pathogens such as Staphylococcus aureus or Eikenella corrodens (often seen in association with human bite injuries). In tenosynovitis infections involving atypical mycobacterium, however, there is absence of pain. Vibrio vulnificus is a species of gram-negative, motile, curved bacterium found in the coastal waters of the United States. Infections from V vulnificus may be caused by direct exposure of an open wound to warm seawater containing the organism or from handling raw seafood or marine wildlife. Infections caused by V vulnificus result in painful cellulitis that progresses rapidly and presents with marked local tissue swelling with hemorrhagic bullae. Bacteremia with systemic symptoms is commonly seen.

Answer 13

The correct response is Option D. The patient described has cervical necrotizing fasciitis (CNF) that likely extends into the mediastinum. Pharyngeal and tonsillar infections, along with dental abscesses, are the most common sources of infection. Diabetes and other immunocompromised states are frequent comorbidities in this disease. Early presentation may be clinically indistinguishable from a superficial soft-tissue infection and, therefore, requires a high index of suspicion. Skin necrosis is often a late finding, as the infection begins in the fascial and deep tissues of the neck. CT scan is usually obtained to define the extent of the disease and may or may not show gas within the soft tissues. Patients are treated with broad-spectrum antibiotics and aggressive surgical debridement. Mastoiditis is an infection of the mastoid air cells usually arising in the setting of untreated otitis media. Mastoiditis can spread to surrounding structures, including the brain. Meningitis is an infection of the meninges that is associated with neck pain as well as fever, headache, and photophobia. It does not present with unilateral neck erythema and swelling. Parotitis is an infection of the parotid gland that usually arises in the setting of an obstructed parotid duct and is a very rare but potential cause of CNF. Sinusitis is not usually associated with CNF but may spread to the orbit, resulting in orbital cellulitis or orbital abscess, and, occasionally, cavernous sinus thrombosis. Cavernous sinus thrombosis is a life-threatening condition.

Answer 14

The correct response is Option B. The most appropriate first step in management in the scenario described is to aspirate fluid from the joint for analysis. There are several conditions that mimic acute hand infections, and it is important to recognize them so that the appropriate treatment can be initiated. Crystalline deposition diseases, such as gout and pseudogout, tend to present with joint swelling, erythema, pain with motion, and fever, much like the signs of infection. The only way to confirm the diagnosis is to aspirate the joint and look for crystals with polarizing microscopy. Though the description of the thumb in the scenario described is consistent with possible infection, the fact that there has been no trauma or break in the skin around the joint, and the patient’s history of acute arthritic episodes in other joints, raises some suspicions that this could be noninfectious. Therefore, joint aspiration to rule out other causes of acute arthritis is warranted. Administration of antibiotics and elevation and splinting should begin after the aspiration, if indicated. MRI of the joint and surgical washout are not indicated at this time.

Answer 15

The correct response is Option C. For the patient described with a penicillin or cephalosporin allergy, trimethoprim-sulfamethoxazole (TMP/SMX) and clindamycin or metronidazole, or a fluoroquinolone and clindamycin or metronidazole, are good antibiotic therapy combinations. Cat bites account for 5 to 15% of animal bites and occur more often in women and adults (median age is 20 years). Most cat bite injuries occur on the upper extremity with 'scratches' on the finger or hand. Infection rates after cat bites range from 50 to 75%. This is typically attributed to the fine, sharp teeth of cats, which produce puncture wounds and penetrate deeply into the soft tissues and joint capsules of the hand. Wounds to the hand demonstrate an increased risk of infection; closed fist injuries have the highest risk. Initial medical management of bite wounds includes ascertaining the rabies status of the animal and updating the tetanus immunization of the patient if necessary. If rabies is suspected, irrigation with povidone-iodine solution will reduce the development by up to 90%. A careful examination of the affected hand/extremity should address the surrounding soft tissues and potential spaces of the hand, tendons, joint and joint capsules, and underlying bone. The wound should be irrigated with saline after obtaining wound cultures. Necrotic tissue should be debrided, and any cat bite with worsening pain will require incision and irrigation of the puncture site. All cat bite wounds should be left open, although large gaping wounds can be loosely approximated. Before definitive surgical treatment of any associated abscess or debridement of devitalized tissue, empiric antibiotic therapy should be started. The majority of cat bite wounds are polymicrobial and the anaerobic organisms are often overlooked. Common aerobic pathogens include Staphylococcus aureus, viridans streptococcus, Corynebacterium, Pasteurella multocida, and various gram-negative enteric organisms. The most common anaerobic pathogens include Bacteroides, Fusobacterium, Peptostreptococcus, and Actinomyces species. Pasteurella multocida, an aerobic, facultative anaerobic gram-negative pathogen, is the most commonly isolated pathogen in cat bites and is present in up to 50% of infected wounds. Symptoms of Pasteurella multocida infection develop rapidly within 24 hours and typically include cellulitis and seropurulent drainage. Other uncommon infections have been reported after cat bites, including tularemia (Francisella tularensis) and cat-scratch disease (Bartonella henselae). Patients with severe wounds (crush injury, joint involvement, deep space infection), cellulitis, sepsis, diabetes, immunosuppression, or other high-risk factors for treatment failure should receive parenteral antibiotics. Alternatives to amoxicillin and clavulanate potassium or ampicillin and sulbactam include other penicillins or cephalosporins, provided they display adequate anaerobic coverage. In the scenario described, the choices containing amoxicillin, ampicillin, and cefazolin are not appropriate because of the patient’s penicillin allergy. Additionally, this patient will require intravenous antibiotics because of the wound severity, so amoxicillin and clavulanate potassium would not be appropriate. The combination of tetracycline and TMP/SMX alone does not provide adequate anaerobic coverage.

Answer 16

The correct response is Option E. Analysis of synovial fluid is the most useful diagnostic test. The most definitive test of the joint fluid, bacterial Gram stain and culture, is unfortunately not consistently positive in an acute septic joint. Culture may be negative in about 50% of cases, especially gonococcal, and Gram stain is even less frequently positive. One has to wait a few days for culture results. As one lowers the threshold for the white cell count in a joint aspirate, the test becomes more sensitive, but less specific. If the white cell count threshold is set at 50,000/mL, which is traditionally the value considered to be the threshold for diagnosis of a septic joint, the sensitivity is 61%. If a white cell count at 17,500 is set as the threshold, the sensitivity is 83%, but specificity is 67%. The specificity rises to 77% if the threshold for the white cell count is raised to 100,000. Sedimentation rate, serum white cell count, and C-reactive protein do little to change pretest probability of a septic joint. Radiographic changes are a late finding in septic arthritis.

Answer 17

The correct response is Option E. A paronychia is an infection occurring in the space between the nail plate and the paronychial or eponychial fold. Common causes include nail biting and aggressive manicuring. In an otherwise healthy individual, Staphylococcus aureus and Streptococcus species are the most common pathogens causing a paronychia. The remaining bacteria listed would only be expected to cause a paronychia in special circumstances. Enterococcus is an enteric bacterium. Mycobacterium marinum can be present in aquatic environments including fish tanks and has also been reported in the Chesapeake Bay. Pasteurella multocida is a common flora of cat mouths. Pseudomonas occurs in areas with moist environments and can be problematic in a burn unit.

Answer 18

The correct response is Option C. Orbital cellulitis may be caused by local extension of a superficial infection such as a hordeolum, or from adjacent infected sinuses, or by hematogenous seeding from a dental or facial abscess. It is important to distinguish between preseptal and orbital cellulitis, which should be suspected when unilateral proptosis is present, and to identify the presence of an intraorbital abscess. Infection within the orbit has implications for management and prognosis due to the effect of high mechanical pressures generated in an unyielding compartment, which will manifest as proptosis, and other symptoms including diplopia, ophthalmoplegia, and chemosis. Orbital cellulitis requires hospitalization and prompt initiation of parenteral antibiotics. An intraorbital abscess can form if treatment is delayed, further compounding the intraorbital pressure and causing tissue necrosis. An intraorbital abscess requires immediate surgical drainage due to risk of blindness. Preseptal cellulitis is an infection of periorbital tissues superficial to the orbital septum, and if the source is from a nearby superficial skin infection, then initial management may be done with oral antibiotics and close follow-up. Preseptal cellulitis from a hematogenous source is more likely to become complicated with orbital cellulitis and abscess if it is not managed with parenteral antibiotics. Infections inside the orbit may extend to the central nervous system and may also cause cavernous sinus thrombosis. CT scan or MRI will confirm intraorbital infection, and related sources such as a facial or dental abscess or a sinusitis, and can direct the surgeon to areas requiring surgical drainage. Blood cultures are useful in identifying the causative organism of the infection during periods of bacteremia, and are an appropriate test in the general workup of the patient; however, blood cultures alone do not diagnose or exclude intraorbital infection. Cell counts are also useful in the general workup of the patient to characterize the systemic impact of the infection, and to be used as a guide in the responsiveness to treatment. The counts do not diagnose or exclude intraorbital infection specifically. On Waters view x-ray studies, increased facial or eyelid edema may be seen as a slight diffuse opacification, but they are unable to delineate orbital and periorbital soft tissues individually. Sinus opacification can be suggestive of active sinusitis and a potential cause of orbital cellulitis. In general, plain x-ray study offers far less information than CT scan or MRI and is not diagnostic of intraorbital infection. Wound swabs are helpful in identifying the causative organism of the infection when there is an obvious source, and are an appropriate test in the general workup of the patient; however, wound swabs alone do not diagnose, exclude, or characterize the extent of intraorbital infection.

Answer 19

The correct response is Option D. Necrotizing fasciitis is a severe soft-tissue infection affecting the skin, subcutaneous tissue, and fascia. It characteristically spares the underlying muscle, progresses quickly, and is associated with high morbidity and mortality rates and severe systemic sepsis. The inciting event is often trauma, even minor trauma and small puncture wounds, but hematogenous spread is also a recognized etiology. The vast majority of patients have some form of chronic debilitating disease that weakens the immune system. Diabetes mellitus appears to be the most common disease, but these may include substance abuse and renal failure. These patients are at higher risk for increased mortality. Two types of necrotizing fasciitis have been described. Type I are mixed aerobic and anaerobic infections, with facultative anaerobic bacteria and non-group A streptococci being present. This is the most common type and is present in about 75% of cases. Type II infections are monomicrobic and are caused by group A Streptococcus species alone or in combination with staphylococcal species. For this reason, antibiotic coverage should be broad. The disease progresses quickly but does evolve through several stages. Initial symptoms include tenderness, erythema, edema, warm skin, and fever; however, symptoms may vary depending on patient characteristics. Initial lab findings may include leukocytosis, thrombocytopenia, and hyperkalemia, but these are variable. When critical skin ischemia occurs, blisters or bullae are formed. In the late stage, lesions turn black and necrotic and are anesthetic as the nerves become involved. Diagnosis begins with a high clinical suspicion in all patients, particularly those with risk factors. Appropriate treatment is surgical debridement, broad-spectrum intravenous antibiotic therapy covering gram-positive, gram-negative, and anaerobic organisms, and careful monitoring and correction of fluid and electrolytes in an intensive care setting. Most authorities agree that hyperbaric oxygen is to be recommended for the treatment of necrotizing fasciitis as an adjunct, if facilities are available and there is no delay in surgical debridement. However, most studies regarding the efficacy of hyperbaric oxygen are anecdotal with a distinct lack of properly designed prospective randomized controlled trials. Mortality rates are reported to be 10 to 75% and are increased in patients with underlying immune compromise, delayed treatment, or involvement of the chest wall.

Answer 20

The correct response is Option E. Of the listed factors relating to risk of postoperative infection in this scenario, the strongest correlation is with contamination type. The Gustilo–Anderson fracture classification has been found to have some correlation with open fracture infection rates, but this relationship is not as strong in the distal radius as it is in long bones of the lower extremity. Recent studies by Glueck, et al, and Swanson, et al, have shown that contamination is a much stronger correlate. A history of systemic illness, such as diabetes mellitus, and the type of fracture fixation seem to have a modest correlation to postoperative infections in distal radius fractures, but the findings are generally not statistically significant. The timing of the initial debridement, as long as it occurs within the first 24 hours of injury, does not significantly affect infection rate. In contrast, there is evidence to suggest that performing multiple serial debridements in significantly contaminated wounds is of benefit in preventing postoperative infection.

Answer 21

The correct response is Option A. Cat bites usually result in puncture wounds because of their long, slender, sharp teeth. It has been reported that as many as 80% of cat bites become infected. Pasteurella species are the most common, occurring in as many as 75% of cat bite infections. Other types of bacteria can also be involved as well, including Streptococci, Staphylococci, and anaerobes. Appropriate antimicrobial treatment for bite wounds must take into account the usual bacteriology of these infections. Pasteurella species are susceptible to penicillin, ampicillin, second- and third-generation cephalosporins, doxycycline, trimethoprim-sulfamethoxazole, fluoroquinolones, clarithromycin, and azithromycin, but are resistant to cephalexin, dicloxacillin, erythromycin, and clindamycin. Appropriate choices for prophylaxis and treatment of cat bite wounds would include amoxicillin and clavulanate or a combination of penicillin plus cephalexin. For those patients who have an allergy to penicillin, moxifloxacin or combination therapy with ciprofloxacin and clindamycin are appropriate choices. Azithromycin may also be effective for the penicillin-allergic patient, but it has less activity against anaerobes. Coverage for community-acquired MRSA (CA-MRSA) infection is not recommended because oral colonization of the human and animal mouth with CA-MRSA is unlikely. Cefazolin, an intravenous form of a first-generation cephalosporin, is not an appropriate treatment for this wound as Pasteurella species are resistant, just as they are to cephalexin, the oral form.

Answer 22

The correct response is Option D. The specific treatment of an extravasation injury is dependent on the drug infused. Application of topical dimethyl sulfoxide has been advocated for the treatment of extravasation of anthracyclines and is supported by several studies. The value of hyperbaric oxygen therapy has not been proven. In the case of doxorubicin extravasation injury, cold compresses may exacerbate the complication by venous constriction, which localizes the drug, whereas hot packs may cause vasodilatation with further extravasation. Inflammation and pain can be managed with anti-inflammatory analgesics. Early excision is rarely performed without evidence of at least ulceration, and the main indication would then be for pain control. In the scenario described, an option would be early surgical debridement and delayed closure of the wound; however, some of the surrounding skin may heal. Thus, a conservative initial approach with later excision after 2 to 3 weeks is recommended since this will give a better cosmetic result.

Answer 23

A) Administration of acyclovir

Answer 24

The correct response is Option C. The patient described has a severe, necrotizing soft-tissue infection, as suggested by tenderness and swelling of the entire limb compartment. Urgent debridement is required. Necrotizing fasciitis must be suspected in any patient with a compromised immune system, even when he or she has a relatively small surface wound. The infection spreads along deep tissue planes €”in this scenario, the muscle fascia. Severe inflammation may result in elevated compartment pressures, requiring fasciotomy. Intraoperative bacterial cultures should guide specific antibiotic therapy. Patients with severe continued or extensive necrosis may benefit from hyperbaric oxygen (HBO) therapy. After all of the necrotic tissue is removed, vacuum-assisted compression (VAC) dressings may be applied to expedite granulation. Definitive closure may involve healing by second intention, skin grafts, or flaps as clinically indicated.

Answer 25

The correct response is Option B. Field management for frostbite includes rapid rewarming of the affected area with circulating water at 104 to 107.6 °F (40 to 42 °C) for a period of 15 to 30 minutes, protection from mechanical trauma, and appropriate analgesia. Next steps in management include elevation, antitetanus prophylaxis, debridement of clear blisters, leaving hemorrhagic blisters intact, and application of aloe vera. Penicillin should be administered for cellulitis. Adjuvant therapies can include anticoagulation, thrombolytics, hyperbaric oxygen, and sympathetic blockade; however, data to support these therapies are scant and equivocal at best. Definitive surgical amputation should be delayed for at least 3 weeks to allow for tissues to demarcate, in terms of viability.

Answer 26

The correct response is Option D. The most likely diagnosis is Fournier disease. Diabetes mellitus, alcoholism, heavy smoking, leukemia, and AIDS can predispose to this condition. Common sources of infection include urogenital disease, trauma, or recent manipulation (iatrogenic trauma, ie, endoscopic procedures). Key steps in treatment include early diagnosis, intravenous hydration, and broad-spectrum antibiotics (anaerobic coverage for Clostridium perfringens should continue as it is difficult to culture this). Immediate surgical debridement along fascial plains is of utmost importance. Orchiectomy is rarely needed, as testicles have their own blood supply and are protected by external spermatic fascia. Mortality rate is quoted to be 7% to 75%, with the higher rate in patients with diabetes, alcoholism, and in cases of delayed diagnosis.

Answer 27

The correct response is Option B. Necrotizing soft-tissue infections are rapidly progressive, polymicrobial infections that require prompt diagnosis, debridement of devitalized tissue, and administration of appropriate antibiotics. Some studies have shown that mortality rates in necrotizing infections can be reduced with the addition of hyperbaric oxygen treatment. High-dose corticosteroids, intravenous gamma globulin, and topical papain-urea ointment have not been shown to increase survival rates of necrotizing soft-tissue infections.

Answer 28

The correct response is Option B. The most appropriate next step in management is to update this patient €™s tetanus status and observe closely for signs and symptoms of envenomation. The area of involvement should be outlined with a marking pen and the patient observed closely for progression of local tissue injury, clinical evidence of coagulopathy, and hemodynamic instability. In the United States, 99% of snake bites are caused by the Crotalidae (pit viper) family of snakes, which includes rattlesnakes, copperheads, and cottonmouths. Rattlesnake bites deliver the most potent venom and are responsible for the majority of fatalities from snake bites; however, 10% to 50% of snake bites have been reported as dry bites. Acute first aid interventions include avoiding excessive activity of the affected site, immobilization in a neutral position, and expeditious transportation to a hospital. Antivenin is not recommended for dry bites (ie, no clinical evidence of envenomation) or if envenomation appears to be mild. Anaphylaxis and serum sickness are potential significant complications of equine antivenin. The general indication for antivenin administration is progressive venom injury. This is defined as worsening local injury (eg, swelling, pain, or ecchymosis), the onset of clinical coagulopathy, or the development of systemic effects including hypotension or changes in mental status. The patient should be monitored closely because the clinical presentation can change rapidly. Antivenin therapy should be instituted if signs or symptoms of envenomation develop or progress. Debridement of the bite site and suction therapy have not been shown to be beneficial in reducing the effects of envenomation and can cause additional necrosis to the tissue under the suction cup. Arterial tourniquets are contraindicated because they may worsen tissue ischemia and necrosis. Fasciotomy should be performed only for clinical signs and symptoms of compartment syndrome. Compartment syndrome and infection from extremity bites are extremely rare.

Answer 29

The correct response is Option E. The patient described has signs and symptoms of a rapidly progressive and advancing soft-tissue infection, which is characteristic of necrotizing fasciitis. The treatment of choice is prompt operative debridement and excision of infected soft tissues and fascia. Necrotizing fasciitis is commonly polymicrobial; Group A hemolytic streptococcus and Staphylococcus aureus are the most common offending agents, although other aerobic and anaerobic bacteria are frequently involved. The infection travels along fascial planes and induces local hypoxia and profound overlying soft-tissue necrosis. Patients with necrotizing fasciitis often require repeat debridements early in the course of treatment to limit the spread of infection. Obtaining blood cultures, adding antifungal antibiotics, elevation, and ice compression do not directly address the surgical emergency of necrotizing fasciitis and would potentially delay treatment. Increasing the dosage of intravenous antibiotics would have little effect on the progression of necrotizing fasciitis. Fasciotomy of compartments is useful for a case of compartment syndrome, but not necrotizing fasciitis.

Answer 30

The correct response is Option A. Cat and dog bite infections have a complex microbiologic mix, with Pasteurella as the most frequent isolate. Common aerobes isolated include streptococci, staphylococci, Moraxella, and Neisseria; common anaerobes include Fusobacterium, Bacteroides, Porphyromonas, and Prevotella. Patients are most often treated with a combination of a β-lactam antibiotic and a β-lactamase inhibitor, such as amoxicillin and clavulanic acid. Alternative treatments include clindamycin plus fluoroquinolone for adults and clindamycin and trimethoprim/sulfamethoxazole for children. Ciprofloxacin does not provide adequate coverage for expected pathogens. In general, cat bites tend to be small puncture wounds that seal almost immediately; thus, wounds should be opened sufficiently to be cleaned and allowed to drain. Dog bite wounds tend to be longitudinal lacerations that are more likely to stay open by themselves. However, canine lacerations, as compared to cat bite punctures, are more likely to result in direct structural damage to nerves, tendons, vessels, and joint structures. Rabies is uncommon in dogs and cats in the United States. Because the cat owner is known, the vaccination record is obtainable. An animal that appears healthy and has been vaccinated should still be quarantined for 10 days to ensure it does not show signs of rabies. If the animal is found to have rabies, postexposure prophylaxis should be started as soon as possible. If the animal is a stray, the animal should be located so it can be tested for rabies. If, however, the animal cannot be located, postexposure prophylaxis is reasonable. Administration of tetanus immune globulin is recommended only for patients with tetanus-prone wounds who have never completed a primary immunization series. If a patient with an acute soft-tissue injury has not been immunized previously, a tetanus toxoid booster is required. The patient must complete the series. If the patient has been immunized previously, a booster dose is given if the last dose was more than five years previously (for a tetanus-prone wound) or more than 10 years previously (for a nontetanus-prone wound). Patients with a contraindication to tetanus toxoid must be managed with tetanus immune globulin alone. Observation alone would not be appropriate for a deep puncture wound with purulent drainage and a mildly elevated leukocyte count. After adequate drainage of the wound and treatment with oral antibiotics, the patient requires follow-up to ensure the infection does not progress, possibly requiring intravenous antibiotics and further surgical drainage.

Answer 31

The correct response is Option E. The most likely causative organism is Streptococcus pyogenes (Group A Strep). Necrotizing soft-tissue infections (necrotizing fasciitis) are rapidly progressive and potentially lethal. Symptoms usually begin with localized erythema and swelling and may mimic cellulitis in the early stages. Severe pain, crepitus, and systemic toxicity can provide clues to the diagnosis. Radiographs may show air in the soft tissues, and patients may exhibit grayish, watery discharge (dishwater pus). These infections can be caused by polymicrobial synergistic infections or may be monobacterial in nature. A recent study showed that group A streptococcus was the most common cause of monobacterial necrotizing fasciitis and that diabetes was the most commonly associated comorbidity. Early intervention and radical debridement are key to management of necrotizing fasciitis. Eikenella corrodens is an anaerobic organism present in human oral flora and has been associated with human bite wounds. Pasteurella multocida is a gram-negative anaerobic bacterium most commonly associated with cat bite infections. Pseudomonas aeruginosa is a gram-negative rod that can be associated with diabetic wound infections. Staphylococcus epidermidis is a gram-positive coccus present on the skin. It has been associated with implant infections. Clostridial and beta streptococcal infections are the most common causes of early-onset necrotizing infection. Diabetes mellitus is the most common morbidity.

Answer 32

The correct response is Option C. Purpura fulminans is a frequently fatal, rapidly evolving syndrome of septic shock and hemorrhagic bullae, which can result in massive desquamation. Management includes prompt recognition of the infection (which is usually caused by Neisseria meningitidis), initiation of broad €‘spectrum antibiotic therapy, mechanical ventilation, and aggressive fluid resuscitation with inotropic support. Disseminated intravascular coagulopathy (DIC) develops, and patients seem to benefit from replacement of activated protein C. A recently published multicenter, retrospective review of 70 patients documented an amputation rate of 90% and suggested the need for early fasciotomy to improve limb salvage. It is difficult to determine tissue viability during the resuscitation period; therefore, debridement, coverage, and amputation are delayed until demarcation has occurred.

Answer 33

The correct response is Option E. The infection described is most likely caused by a subset of Staphylococcus aureus, which is methicillin €‘resistant. Although methicillin €‘resistant S. aureus (MRSA) has traditionally been iatrogenic in its etiology, community €‘acquired MRSA is becoming more prevalent. In the Emergency Department population, the proportion of soft tissue infections presenting with MRSA is increasing. MRSA is not sensitive to penicillin €‘related antibiotics such as piperacillin/tazobactam and typically requires vancomycin or linezolid for effective treatment. Older antibiotics such as clindamycin and trimethoprim €‘sulfamethoxazole may also be effective in treating MRSA. MRSA takes longer than the other bacteria listed to grow out in culture. Bacteroides fragilis, Escherichia coli, group B streptococcus, and Pseudomonas aeruginosa are all common bacteria found in abscesses of the hand; however, they are all sensitive to penicillin €‘related antibiotics such as piperacillin/tazobactam.

Answer 34

The correct response is Option B. Necrotizing fasciitis is a severe form of subcutaneous infection that tracks along fascial planes often extending beyond the superficial signs of infections. Early diagnosis and treatment are critical in reducing mortality. Early surgical intervention is often required for diagnosis and treatment. Initial antibiotic therapy is directed at the most likely pathogens. Two clinical subtypes of necrotizing fasciitis have been identified. Type I is a polymicrobial infection caused by aerobic and anaerobic bacteria occurring primarily in patients who are immunocompromised or have certain chronic diseases like diabetes. Type II is a monomicrobial infection that can occur in healthy individuals in any age group. Often, the individual has a history of blunt trauma, penetrating injuries or lacerations (often minor), surgical procedures, childbirth, or burns. In Type II fasciitis, the most common causative organisms are group A streptococci. Clindamycin and penicillin in combination are recommended. Clindamycin has been shown to suppress toxin production, whereas metronidazole has not. Clindamycin also facilitates phagocytosis of Streptococcus pyogenes. Penicillin is added because of increasing resistance of group A streptococci to clindamycin. Infection with Staphylococcus aureus is a less common cause of Type II necrotizing fasciitis. Oxacillin could be used to treat susceptible S. aureus infection, whereas vancomycin is appropriate therapy for methicillin-resistant S. aureus (MRSA). Type I necrotizing fasciitis requires a multiple antibiotic regimen to cover aerobic and anaerobic bacteria. Therefore, broad €‘spectrum coverage with ampicillin €‘sulbactam, clindamycin, ciprofloxacin, or gentamicin is recommended.

Answer 35

The correct response is Option E. Hidradenitis suppurativa is an inflammatory disease of the apocrine glands and follicular epithelium, presenting most commonly as deep recurrent infections or chronic sinus tracts in hair-bearing regions of the skin. It is most commonly seen in the axillary region in young women, but the groin and perineum may also be affected. After the diagnosis has been confirmed, a short course of treatment with local drainage and suppressive antibiotics is appropriate. However, once the disease process is established, the only appropriate therapy is complete excision of the scarred area. The successful treatment of chronic hidradenitis with injection of botulinum toxin A has been reported. Sweat glands have a sympathetic innervation. Botulinum toxin works by blocking the release of acetylcholine from nerve endings, thus decreasing sweat production. However, this is expensive and represents a temporary treatment of a chronic problem. The mainstay of treatment for larger areas is complete excision of axillary skin followed by split-thickness skin grafting. Negative pressure dressings are helpful to stabilize the graft. Although numerous local fasciocutaneous pedicled and free flaps have been described, they increase the risk of donor site morbidity and are generally not necessary. Healing by secondary intention has also been described. However, it is preferable to undertake excision of one axilla at a time so the patient is not disabled in the perioperative period.

Answer 36

The correct response is Option C. The radial and ulnar bursas are connected through the Parona space, which lies between the pronator quadratus fascia and the flexor digitorum profundus tendon sheath. The flexor tendon sheath of the small finger often connects with the ulna bursa, which extends proximal to the transverse carpal ligament. This connection can give rise to a €œhorseshoe abscess. € This abscess results when an infection starting in the thumb or small finger progresses proximal through the wrist and then into the opposite flexor tendon sheath through the Parona space. The Parona space can be explored by performing an extended carpal tunnel release. Another potential space in the hand is the thenar space, which is bordered ulnarly by the vertical septum between the flexor sheath and metacarpal of the long finger, dorsally by the fascia of the adductor pollicis, and radially by the thenar muscle fascia. It should be noted that this space does not include the thenar muscles. The midpalmar space is bordered radially by the vertical septum between the flexor sheath and metacarpal of the long finger, dorsally by the fascia over the interossei of the third and fourth web spaces, ulnarly by the fascia over the hypothenar muscles, and volarly by the flexor tendons. The posterior adductor space is defined as the space dorsal to the adductor pollicis and volar to the first dorsal interosseous. The dorsum of the hand contains the posterior interosseous space, which is dorsal to the first dorsal interosseous. The ring finger would be explored if the patient had displayed signs of tenosynovitis of this digit.

Answer 37

The correct response for Item 198 is Option B and for Item 199 is Option E. Septic arthritis may result from extension of an adjacent subcutaneous abscess or by intra-articular contamination caused by a laceration or puncture wound. The joint is a poorly vascularized potential space, favoring colonization. Early diagnosis and drainage are crucial to treatment, as a joint infection can progress rapidly to destruction of articular cartilage. The two most common organisms that cause hand infections are Staphylococcus aureus and B €‘hemolytic streptococci. Minor staphylococcal and streptococcal infections are treated with first-generation cephalosporins. More significant infections of the interphalangeal joint should be performed through a midaxial incision. Neisseria gonorrhoeae usually manifests as a primary venereal infection. However, it can disseminate and sometimes present as a secondary hand infection, which is often confused with a purulent tenosynovitis or arthritis. It is important to distinguish gonococcal from pyogenic infection because, unlike a pyogenic infection, a gonococcal infection does not usually destroy tendon or articular cartilage. Therefore, incision, drainage, and debridement are unnecessary and should be avoided. Disseminated gonococcal infection is the most common cause of acute infectious arthritis in sexually active adults. A history or evidence of trauma are lacking. Fluid aspiration with Gram staining for gram €‘negative diplococci allows definitive diagnosis. Hospitalization and intravenous administration of a third €‘generation cephalosporin is recommended. Manifestations of Sweet syndrome can masquerade as acute hand infections. Sweet syndrome, originally described as an acute febrile neutrophilic dermatosis, belongs to a class of skin lesions that histologically have intense epidermal and/or dermal inflammatory infiltrate of neutrophils without evidence of infection or vasculitis. The lesions can erupt at sites of minor trauma. The clinical picture is consistent with infection initially. The unresponsiveness of these lesions to antimicrobial therapy and the lack of associated cellulitis is a clue to the diagnosis. The treatment of choice involves a tapering dose of corticosteroids. Herpetic whitlows are often confused with paronychia or felon and are treated mistakenly as such. Initial signs include intense pain and erythema of the fingertip, followed by edema and tenderness. A Tzanck smear of vesicular fluid may show multinucleated giant cells. Primary herpes simplex infections typically resolve without treatment within three weeks. Incision and drainage of herpetic whitlow is contraindicated because surgical treatment converts a closed wound to open and may result in a secondary bacterial infection or viral superinfection. To date, there have been no controlled studies that assess the efficacy of acyclovir for the treatment of herpetic whitlow, but case reports suggest that it both suppresses and decreases the length and severity of recurrent infections when taken orally.

Answer 38

The correct response for Item 198 is Option B and for Item 199 is Option E. Septic arthritis may result from extension of an adjacent subcutaneous abscess or by intra-articular contamination caused by a laceration or puncture wound. The joint is a poorly vascularized potential space, favoring colonization. Early diagnosis and drainage are crucial to treatment, as a joint infection can progress rapidly to destruction of articular cartilage. The two most common organisms that cause hand infections are Staphylococcus aureus and B €‘hemolytic streptococci. Minor staphylococcal and streptococcal infections are treated with first-generation cephalosporins. More significant infections of the interphalangeal joint should be performed through a midaxial incision. Neisseria gonorrhoeae usually manifests as a primary venereal infection. However, it can disseminate and sometimes present as a secondary hand infection, which is often confused with a purulent tenosynovitis or arthritis. It is important to distinguish gonococcal from pyogenic infection because, unlike a pyogenic infection, a gonococcal infection does not usually destroy tendon or articular cartilage. Therefore, incision, drainage, and debridement are unnecessary and should be avoided. Disseminated gonococcal infection is the most common cause of acute infectious arthritis in sexually active adults. A history or evidence of trauma are lacking. Fluid aspiration with Gram staining for gram €‘negative diplococci allows definitive diagnosis. Hospitalization and intravenous administration of a third €‘generation cephalosporin is recommended. Manifestations of Sweet syndrome can masquerade as acute hand infections. Sweet syndrome, originally described as an acute febrile neutrophilic dermatosis, belongs to a class of skin lesions that histologically have intense epidermal and/or dermal inflammatory infiltrate of neutrophils without evidence of infection or vasculitis. The lesions can erupt at sites of minor trauma. The clinical picture is consistent with infection initially. The unresponsiveness of these lesions to antimicrobial therapy and the lack of associated cellulitis is a clue to the diagnosis. The treatment of choice involves a tapering dose of corticosteroids. Herpetic whitlows are often confused with paronychia or felon and are treated mistakenly as such. Initial signs include intense pain and erythema of the fingertip, followed by edema and tenderness. A Tzanck smear of vesicular fluid may show multinucleated giant cells. Primary herpes simplex infections typically resolve without treatment within three weeks. Incision and drainage of herpetic whitlow is contraindicated because surgical treatment converts a closed wound to open and may result in a secondary bacterial infection or viral superinfection. To date, there have been no controlled studies that assess the efficacy of acyclovir for the treatment of herpetic whitlow, b

Answer 39

The correct response in Option B. Staphylococcal folliculitis is the most common form of infectious folliculitis. One or more pustules may appear, usually without fever or other systemic symptoms, on any body surface. Staphylococcal folliculitis may occur because of injury, abrasion, or nearby surgical wounds or draining abscesses. The two gram-positive cocci, Staphylococcus aureus and Streptococcus pyogenes (group A), account for the majority of skin and soft tissue infections. The streptococci are secondary invaders of traumatic skin lesions and cause impetigo, erysipelas, cellulitis, and lymphangitis. S. aureus invades skin and causes impetigo, folliculitis, cellulitis, and furuncles. Elaboration of toxins by S. aureus causes the lesions of bullous impetigo and staphylococcal scalded skin syndrome.

Answer 40

The correct response is Option C. In this clinical scenario of a snakebite to the upper extremity, the patient meets criteria for moderate envenomation, which can also yield orthostatic changes and mild coagulation parameter changes. Guidelines for management include the administration of 10 to 20 vials of antivenin after skin testing with horse serum for possible hypersensitivity reaction. Criteria for minimal envenomation include fang marks, local swelling or pain, and no systemic reaction; therapy includes delivery of up to five vials of antivenin. Severe envenomation can produce subcutaneous ecchymosis, marked swelling of the extremity, coagulopathy, shock, and compartment syndrome; therapy includes delivery of 20 or more vials of antivenin (without delaying for skin testing), resuscitation with correction of acidosis and coagulopathy, and fasciotomy for compartment pressures greater than 30 mmHg or worsening findings on neurologic examination. Tourniquets and cryotherapy, although used in the past, are controversial and may be associated with increased tissue damage. Resuscitation should be performed with lactated Ringer’s solution. Normal saline is contraindicated because this solution will exacerbate metabolic acidosis due to its high chloride load (154 mEq/l). In a series of 107 patients with pit viper snakebites managed at a university teaching hospital in the southeastern U.S., 27% of patients underwent surgical debridement and 4% of patients required fasciotomies. Antivenin was administered to 34 patients, and serum sickness developed in nine patients. Coagulopathy was present in 4% of patients, and no deaths were reported. Copperhead bites accounted for 68% of all envenomations.

Answer 41

The correct response is Option A. Tuberculosus tenosynovitis is the most frequent tuberculosus infection in the hand. It may clinically simulate rheumatoid tenosynovitis. The most common pathogen is Mycobacterium marinum. Radiographs often show no abnormalities and pathology alone will often show only nonspecific tenosynovitis, but granulomas may be present. Cultures must be requested at 30 degrees Celsius to identify M. marinum. There are several diagnostic clues for tuberculous tenosynovitis, such as proliferative synovitis occurring in the absence of a known rheumatoid or collagen vascular disease as well as the presence of rice bodies during surgical exploration. Rice bodies are infected villous bodies on the synovial surface that break off and become trapped within the inflammatory mass. CT scan of the abdomen is sometimes recommended for women with palmar fibromatosis and arthritis because this condition may be associated with ovarian cancer. Amyloidosis can cause tenosynovitis and carpal tunnel syndrome but does not commonly produce rice bodies. Allopurinol is a treatment for gout, and potassium hydroxide stains are used to identify fungus.

Answer 42

The correct response is Option E. Bite injuries resulting from fistfights usually occur over the dorsal aspect of the third, fourth, or fifth metacarpophalangeal joint where a tooth penetrates the skin, extensor tendon, potentially the joint capsule, and even bone. When the hand is opened, the inoculating bacteria are dragged proximally by the extensor tendon and soft tissue. The patient may present acutely before clinical signs of an infectionCwith what appears to be a simple laceration or abrasion over the metacarpophalangeal jointCbut more typically after signs of infection have developed. If there are no signs of infection, it is prudent to explore the wound to rule out injury to the extensor tendon, joint capsule, and cartilage. To do so, the hand must be examined through the entire range of motion, particularly with the fingers flexed as in a clenched fist position. If there is no injury to the deeper structures, the wound can be washed out and the skin left open to heal by second intention. The patient can then be discharged with prophylactic antibiotics to cover the most common bacteria isolated from human bite wounds, i.e., Staphylococcus aureus, followed by Streptococcus species, Corynebacterium species, and Eikenella corrodens. Follow-up within 24 to 48 hours is important in outpatient management of these injuries. If injury is noted to the tendon, joint capsule, or joint cartilage, then operative washout and admission for intravenous antibiotics is appropriate. When the patient presents with a well-developed infection, antibiotic therapy alone is insufficient. Careful exploration must be performed to rule out injury and infection to deeper structures, most importantly the joint. Unrecognized or untreated pyarthrosis can lead to joint destruction and osteomyelitis. Inadequate exploration in the emergency department is usually due to inadequate anesthesia. Formal washout and drainage is sometimes best performed in the operating room. Elevation and immobilization are important in the management of edema in patients with hand infections. In the clinical scenario presented, however, this alone would be insufficient treatment because surgical drainage of the joint is required.

Answer 43

The correct response is Option D. Infections of the index finger drain from the flexor sheath proximally into the thenar space. Infections of the long, ring, and small fingers drain into the midpalmar space. The radial and ulnar bursae communicate by Parona’s space, which lies deep to the pronator muscle.

Answer 44

The correct response is Option E. Staphylococcus aureus and viridans streptococcus are the two most commonly isolated organisms in hidradenitis suppurativa. As a result, initial management should include empiric administration of antibiotics effective against these organisms until the results of cultures are received. Hidradenitis suppurativa is a condition that is poorly understood but is thought to result from chronic infection of the apocrine sweat glands. Although the axillae are affected most commonly, the perineum, groin, and genitalia may also be involved. Extensive scar tissue and fistula tracts develop over time, and the condition becomes progressively more difficult to treat. In patients with hidradenitis, appropriate management is application of warm compresses, incision and drainage of the appropriate areas, and administration of antibiotics. Patients with more severe cases should undergo excision of the involved skin and subcutaneous tissue followed by coverage with a local flap or skin graft. Investigational studies of a method of immunotherapy, based on the staphylococcal phage lysate vaccine, have shown promising results in patients with chronic hidradenitis suppurativa.

Answer 45

The correct response is Option C. This 6-year-old boy has purpura fulminans, an uncommon illness that typically affects young children but can also occur in adults. Purpura fulminans often develops in association with a predisposing condition. It manifests as severe hemorrhage and necrosis of skin associated with disseminated intravascular coagulation. Affected patients have petechial rashes, which progress to confluent areas of ecchymosis, and then to necrotic, hard, full-thickness eschar. Bilateral symmetric gangrene of the extremities necessitates amputation in as many as 20% of patients. Reconstructive procedures, including free tissue transfer, are frequently required to resurface necrotic areas and salvage extremities with exposed joints. Septic shock and organ failure may also result. Mortality rates have been reported to be as high as 60%. Purpura fulminans is associated with endotoxin-producing bacteria. Although Neisseria meningitidis is the most common causative organism, Streptococcus pneumoniae, Haemophilus influenzae, and Rickettsia have also been implicated. The mechanism of this condition is believed to be liposaccharide-mediated endothelial damage caused by bacteria, leading to decreased serum levels of proteins C and S. Skin necrosis results from a low-flow coagulative state and microemboli. Management of affected patients includes general hemodynamic support, intravenous administration of an appropriate antibiotic, wound care, eventual soft-tissue reconstruction, and amputation when necessary.

Answer 46

The correct response is Option B. The midpalmar space is one potential site of infection of the palm; others include the subcutaneous tissue, tendon sheaths, and thenar and hypothenar eminences. The midpalmar space is located deep to the flexor tendon. It extends dorsally to the fascia over the second and third volar interossei and the third and fourth metacarpals. The midpalmar space is bordered radially by a fascial septum extending from the third metacarpal to the flexor sheath of the flexor digitorum profundus tendon of the long finger, and ulnarly by the fascia of the hypothenar musculature. The proximal margin of the midpalmar space is a thin layer of fascia that lies just distal to the carpal canal. The distal margin of the midpalmar space is bordered by vertical septa of the palmar fascia, which extend almost to the web spaces. In patients with infection of the midpalmar space, diagnosis is often delayed. Affected patients typically exhibit swelling of the dorsal aspect of the hand, loss of palmar concavity, and difficulty extending and flexing the fingers. Marked tenderness in the midpalmar area is characteristic, and cellulitis is often associated. The thenar space is located radial to the vertical septum between the third metacarpal and the flexor digitorum profundus tendon of the long finger; it extends to the radial edge of the abductor pollicis brevis tendon. The hypothenar space contains the hypothenar muscles and is enveloped within the fascia of these muscles. It is bordered radially by a fascial septum extending from the fifth metacarpal bone to the palmar fascia.

Answer 47

The correct response is Option D. In this patient who has septic arthritis affecting the proximal interphalangeal joint of the index finger, the most likely cause is infection with Staphylococcus aureus organisms. Staphylococcus aureus is an anaerobic gram-positive coccus that is present on the skin and is a frequent cause of skin and soft-tissue infections. It is the most common cause of septic arthritis of the hand and wrist. Eikenella corrodens, an anaerobic gram-negative rod, is present in the human mouth and is more likely to be cultured from a human bite wound. Septic arthritis resulting from Neisseria gonorrhoeae is more likely to occur in young men who are sexually active. Affected patients typically have a history of migratory polyarthralgia. Serratia species are a frequent cause of infection in persons who abuse intravenous drugs as well as patients with diabetes mellitus or immune system compromise. Streptococcus species, including viridans streptococcus, are the second most common causative organism in patients with septic arthritis of the hand.

Answer 48

The correct response is Option C. This patient has a dystrophic nail resulting from a fungal infection (onychomycosis). The diagnosis of onychomycosis can be confirmed by positive findings on fungal culture. Fungal infections are the underlying cause of dystrophic nails in approximately 50% of affected patients; the remaining 50% are caused by other factors, including psoriasis, lichen planus, and trauma. Although they are more common in the foot, fungal infections can cause functional and aesthetic deformities in the fingernails. In the past, long-term administration of antifungal agents was recommended; however, this treatment course was associated with significant toxicity, requiring monitoring of hepatic function, and often disappointing results. More recently, terbinafine and itraconazole have offered new treatment options. This agents are administered for six weeks, and hepatic function is monitored only in those patients who have a history of hepatitis, liver disease, or heavy alcohol use. However, adverse effects associated with terbinafine use include Stevens-Johnson syndrome, neutropenia, hepatotoxicity, hepatic failure, erythema multiforme, toxic epidermal neurolysis, and anaphylaxis. In addition, terbinafine is far more costly than previously used antifungal agents. Topical or oral administration of antibiotics would not be expected to improve this fungal infection. In addition, topical antibiotics may aggravate the nail matrix. Resection of the sterile matrix and replacement with a graft is associated with a high incidence of recurrence and morbidity. Removal of the nail would not eliminate the fungal infection within the underlying matrix.

Answer 49

The correct response is Option E. This 34-year-old man has findings consistent with advanced flexor tenosynovitis. The diagnosis can be made by the presence of one or more of Kanavel’s four signs (fusiform swelling, partial flexed posturing of the finger, tenderness over the flexor tendon sheath, and pain with passive extension of the finger). This patient exhibits three of the diagnostic signs, indicating an advanced disease course. In addition to intravenous administration of antibiotics, the most appropriate management is opening and irrigation of the flexor tendon sheath. The surgeon should make an incision into the palm that is sufficiently wide to allow for access to and visualization of the proximal aspect of the A1 pulley. Another incision is made distally to allow access to the A4 and A5 pulleys. If necessary, the incisions can be extended distally and/or proximally to treat infected, necrotic tissue. In patients with advanced flexor tenosynovitis, the flexor digital sheath is typically distended with purulent material. A plastic irrigation catheter is inserted at the level of the A1 pulley and threaded distally into the sheath to allow for irrigation beyond the A5 pulley. This technique will facilitate complete decompression of the sheath without sacrificing the pulleys. Irrigation can be provided via the catheter continuously for as long as 24 hours, depending on the severity of infection. Needle aspiration is useful in establishing a diagnosis of or treating early tenosynovitis (characterized by the presence of only one or two of Kanavel’s signs) or as initial treatment during pregnancy. Simple incision into the finger, joint, or palm will not address in the infection of the flexor tendon sheath.

Answer 50

The correct response is Option E. This 48-year-old nurse has findings consistent with streptococcal toxic shock syndrome caused by invasive infection with Streptococcus organisms. This condition is characterized by pain disproportionate to the level of injury. Affected patients typically have other minor symptoms, in addition to pain, and have been known to seek treatment frequently before the correct diagnosis is established. Streptococcal toxic shock syndrome is confirmed by the presence of coagulation difficulties and hepatic and renal abnormalities. Clostridial necrotizing fasciitis has symptoms similar to streptococcal toxic shock syndrome but is differentiated by subcutaneous emphysema and air in the tissues on radiographs. With anthrax contamination, primary routes of inoculation are cutaneous and inhalational. Cutaneous anthrax is characterized by a single lesion that initially resembles an insect bite but then becomes ulcerated. Skin trauma is not associated. Pseudomonas ecthyma gangrenosum is an infection that demonstrates rapid progression and is frequently fatal. It occurs in patients with febrile neutropenia, and is often a complication of chemotherapy administered for lymphoreticular malignancies. Although staphylococcal cellulitis is not associated with systemic manifestations, patients with staphylococcal toxic shock syndrome can have failure of multiple organ systems.

Answer 51

The correct response is Option D. This patient has a collar button abscess, which communicates from the volar web space to the dorsal aspect of the hand via the palmar fascia or lumbrical canal. Finger abduction is a characteristic finding. Appropriate management is drainage of the abscess using a combined volar and dorsal approach. The extensor tendons do not lie within sheaths on the dorsal aspect of the hand. Infection of the flexor tendon sheath is known as flexor tenosynovitis. This condition is diagnosed by the presence of one or more of Kanavel’s signs, including fusiform swelling, partial flexed posturing of the finger, tenderness over the flexor tendon sheath, and pain with passive extension of the finger. Finger abduction is not associated. Patients with infection of the palmar bursa have a painful prominence in the palm without finger abduction. Parona’s space lies between the pronator quadratus and flexor digitorum profundus tendons. It communicates with the flexor tendon sheaths to the thumb and small finger (radial and ulnar palmar bursa) and the midpalmar space. Infection within this space is characterized by painful swelling over the volar aspect of the wrist that occurs proximal to the flexion crease of the distal wrist.

Answer 52

The correct response is Option D. In a patient who has been bitten by a potentially rabid animal and who has not been previously vaccinated, management should include wound care and administration of both rabies immune globulin (RIG) and rabies vaccine. Because rabies incubation periods of more than one year have been reported in humans, the prophylactic regimen should be initiated immediately in any person who has been bitten by an animal with suspected or proven rabies regardless of the length of the delay, as long as clinical signs of rabies are not present. Studies have shown that a regimen of one dose of RIG and five doses of human diploid cell vaccine (HDCV) over a 28-day period is a safe treatment protocol that induces an excellent antibody response. Immediate, thorough washing of all bite wounds and scratches with soap and water and irrigation with a virucidal agent (such as a povidone-iodine solution) are also important for preventing rabies. Experimental animal studies have shown that thorough wound cleansing alone without other postexposure prophylaxis markedly decreased the likelihood of rabies. In addition, tetanus prophylaxis and measures to control bacterial infection should be administered as indicated. Suturing of large wounds should be based on cosmetic factors and the potential for bacterial infection. Prophylactic administration of both passive antibody and vaccine is indicated in all exposed patients except for those who have previously received complete vaccination regimens (preexposure or postexposure) with a cell culture vaccine or those persons who have been vaccinated with other types of vaccines and have had documented rabies antibody titers. Instead, these persons should receive the vaccine only. This combination of RIG and vaccine is also recommended for patients who have been exposed to rabies without specifically being bitten.

Answer 53

The correct response is Option D. Tenosynovitis is a bacterial infection within the sheath of the extrinsic flexor tendons of the hand. Suppurative infection of the sheath can develop over time. Classic signs of tenosynovitis include fusiform swelling, partial flexed posturing of the digit, and tenderness along the flexor tendon sheath; however, other inflammatory processes can cause these findings. In contrast, the fourth classic sign, pain with passive extension of the digit, is the most sensitive test for flexor tenosynovitis. Aspiration of the affected tendon sheath will yield purulent drainage. Diagnosis can be confirmed with Gram's stain. In patients with established tenosynovitis, the most appropriate management is surgical irrigation and/or drainage of the tendon sheath. This is best accomplished with a proximal incision at the level of the A1 pulley and a distal incision at the distal flexor crease; the fibroosseous canal is then irrigated copiously. In patients with more extensive infection, open drainage and debridement may be required. Drainage from a finger wound is more likely to be caused by local wound infection than by tenosynovitis.

Answer 54

The correct response is Option E. The most likely diagnosis is tenosynovitis, an infection involving the gliding surface of the flexor tendon sheath that typically develops following a puncture wound. Staphylococcus aureus is the most likely causative organism. The four essential signs of tenosynovitis are fusiform swelling, partial flexed posturing of the digit, tenderness along the flexor tendon sheath, and pain with passive extension of the digit. Cellulitis is a common superficial infection that typically affects the dorsal aspect of the hand and is characterized by erythema, edema, and lymphangitis. Beta-hemolytic streptococcus is most frequently associated. Felons are infections of the pulp space (which is compartmentalized by septa) typically caused by Staphylococcus aureus. Although tenosynovitis may develop in a patient with an advanced felon, the infection is more likely to be localized at the pulp initially, and the patient would have throbbing pain, especially when the finger is placed in a dependent position. Patients with osteomyelitis have localized pain, swelling, and erythema along the course of one of the long bones of the hand. This condition often develops secondary to localized infection by hematogenous spread. In patients with paronychia, the structures surrounding the proximal and lateral nail become infected. This condition is characterized by pain, especially in the region of the nail fold, and erythema. Staphylococcus aureus is the most frequently identified cause of acute paronychia, and Candida albicans is most likely to cause chronic paronychia.

Answer 55

The correct response is Option D. In this patient who has had the spontaneous onset of cellulitis of the arm after undergoing axillary lymph node dissection, the most appropriate management is intravenous administration of an antistreptococcal antibiotic. Fever and leukocytosis are typically associated with cellulitis but are not required to make the diagnosis, as many of these patients will be afebrile and will not have an increased leukocyte count or absolute neutrophil count on serologic testing. Anti-streptolysin O titer may be positive. Although lymphatic massage and compression and elevation of the extremity are useful in controlling the lymphedema associated with lymph node dissection, these measures will not treat cellulitis. Antibiotic therapy should not be based on the results of blood or tissue aspirate cultures because these often do not yield any growth. Topical application of an antibiotic will not effectively treat cellulitis. Incision and drainage of the affected site is not indicated.

Answer 56

The correct response is Option C. This patient has chronic paronychia, which is a recurrent abscess beneath the eponychial edge of the fingernail associated with repeated exposure to a moist environment. In patients with this condition, Candida albicans is the most frequently cultured organism. Chronic paronychia can evolve following an acute episode if drainage of the abscess is inadequate or inappropriate antimicrobial agents are prescribed. Removal of a segment of nail plate is indicated in patients with acute paronychia if there is drainage beneath the plate. In a patient who has paronychia that appears to be caused by a fungal organism, management should focus on administering oral and topical antifungal agents, such as itraconazole and ketoconazole, and minimizing the moist environmental conditions that have predisposed the patient to the infection. If the infection does not respond to treatment, radiographs should be obtained to determine bony involvement. In addition, biopsy specimens and cultures of soft tissue and/or bone may be indicated to identify the pathology of the condition, as the underlying cause may be a misdiagnosed malignant tumor. If radiographs, biopsy specimens, and cultures show no disease, appropriate management is excision of the thickened dorsal nail roof (ie, marsupialization), typically a crescent-shaped piece with a width of 3 to 5 mm. Simple repeat incision and drainage alone will not prevent recurrence. Obliteration of the nail matrix or amputation of the fingertip will not address the symptoms.

Answer 57

The correct response is Option D. This patient's findings are most consistent with toxic shock syndrome. This condition should be suspected in any patient who has fever, hypotension, and erythroderma following surgery, trauma, or infection of structures related to the skin or nares. Symptoms include a temperature greater than 38.9%C (102%F), a diffuse macular rash, and a systolic blood pressure of less than 90 mmHg in adults or less than the fifth percentile for children younger than 16 years. Syncope and orthostatic hypotension are also common. Desquamation of the palms and soles typically occurs one to two weeks after the onset of illness. Appropriate management should include supportive treatment for multisystem organ involvement, antibiotics effective against Staphylococcus aureus, and identification and treatment of the focus of bacterial toxin production. Although the Staphylococcus organisms that produce toxic shock syndrome toxin typically do not produce purulent wounds and the surgical wound may appear normal, an undrained focus of infection may be present in the wound. Therefore, the wound should be debrided to locate any potential source of toxin-producing organisms and to provide tissue for bacterial culture. Acute gastroenteritis is associated with the abrupt onset of hypotension and abdominal symptoms such as nausea and diarrhea. Erythroderma is not an associated finding. Kawasaki disease is a multisystem disease typically seen in children younger than 7 years and characterized by prolonged fever, lymphadenitis, conjunctivitis, and erythema of the mucous membranes. Thrombocytosis and desquamation of the distal digits occur during the recovery phase. Hypotension is rare. Infection with Staphylococcus aureus and/or Streptococcus pyogenes is not associated. Patients with Stevens-Johnson syndrome have a systemic, widespread rash that also affects the mucous membranes. This condition can result from infection, illness, or an allergic reaction to medication. Systemic symptoms are typically severe. In patients with urosepsis, the onset of septic shock can be typically distinguished from toxic shock syndrome by the absence of erythroderma. Profuse watery diarrhea is uncommon in patients with urosepsis but occurs frequently in patients with toxic shock syndrome.

Answer 58

The correct response is Option D. The brown recluse spider (Loxosceles reclusa) is one of two species of North American spider capable of envenomation. It is generally found throughout the southern United States. This spider is believed to be nocturnal but may also be active during the day; it does not weave a web. Features include long slender legs and a distinctive fiddle-shaped marking on its dorsal cephalothorax. Both male and female brown recluse spiders are venomous. Most patients are unaware that they have been bitten by this spider until pain develops or the wound becomes noticeable. Blistering, ischemia, and ulceration may be seen and can ultimately lead to necrosis. Conservative treatment with administration of dapsone 100 mg daily for 14 days is advocated as the injury is often more extensive than initially thought. There is no antivenin to brown recluse spider venom. Dapsone is a leukocyte inhibitor that has both bacteriostatic and bacteriocidal properties and is frequently used in the treatment of leprosy. Hemolysis is the most common adverse effect of dapsone therapy. Because of the risk for hemolysis and other hematologic side effects, including methemoglobinemia, blood counts should be measured weekly. In addition, dapsone should not be administered to patients who have glucose-6 phosphate dehydrogenase deficiency. Diarrhea, diplopia, headache, and peripheral neuropathy are not complications of dapsone therapy.

Answer 59

The correct response is Option A. Because scorpion stings are typically self-limiting in adults, management should be limited to observation and application of cold compresses. Six closely related species of scorpion found in the southwestern United States cause medically significant injuries resulting from a sting. These species are typically 1 to 7 cm long and yellow-brown in color, possibly with vertical bands. The venom is neurotoxic, resulting in activation of the autonomic nervous system and depolarization of the neuromuscular junctions. Affected patients have intense localized pain and hyperesthesia; there is severe pain with light tapping over the area of the wound. Other symptoms seen in patients who sustain scorpion stings include blurred or diminished vision, strabismus, dyspnea, wheezing, dysphagia, urinary or fecal incontinence, opisthotonos, fever, and involuntary muscle contractions. Hospital admission is recommended for children who have scorpion stings because envenomation is much more dangerous than in adults. Appropriate pediatric management includes airway control, sedation, cardiac monitoring for potential arrhythmias, and administration of calcium gluconate for treatment of muscle spasms. Narcotic agents should not be administered as they may exacerbate the neurotoxic effects. Scorpion antivenin is available for use in Arizona. The use of tourniquets is not recommended in patients with scorpion stings. Debridement is not necessary because scorpion venom has only localized adverse effects on soft tissue.

Answer 60

The correct response is Option A. This patient has compartment syndrome due to a snake bite. Pain is the hallmark of compartment syndrome and is accentuated by passive stretching of the involved muscle compartment, which is the most consistent early sign. Patients with injuries of the upper and lower extremities should be closely monitored for the presence of muscle, nerve, and tissue ischemia. However, compartment syndrome occurring in conjunction with a pit viper or other snake bite is often worse than other types of compartment syndrome. Because the venom is injected directly into the tissues, tissue destruction occurs rapidly, leading to the immediate onset of edema, ecchymosis, and swelling. Measurement of compartment pressures is an important step in the diagnosis of compartment syndrome, especially in patients who have sustained head trauma or spinal cord injuries. Decompressive fasciotomy should be performed in normotensive patients when compartment pressures are greater than 30 mmHg and the duration of symptoms is longer than eight hours or is unknown or the patient is unconscious or uncooperative. Patients with hypotension and compartment pressures greater than 20 mmHg should also undergo surgery within six hours. In some patients with compartment syndrome, central or peripheral sensory deficits or late nerve ischemia may preclude the presence of pain as a diagnostic finding. In compartment syndrome, distal pulses may still be present. The affected extremity may appear cyanotic, pale, or normal. Sensation may be normal or diminished. Tenseness and tenderness of the closed compartments are nonspecific findings that are not necessarily associated with ischemic tissue damage.

Answer 61

The correct response is Option A. Adjunctive treatment in this patient should include antibiotic prophylaxis against Aeromonas hydrophila organisms. This is a symbiotic bacteria found in the intestines of medicinal-grade leeches of the Hirudo medicinalis species, which can be applied to flaps or replanted limbs in order to alleviate venous congestion. The Aeromonas bacteria produces digestive enzymes that act to break down hemoglobin within the intestines of the leech. However, patients with devitalized vascular tissue are particularly susceptible to infection with this gram-negative organism. Affected patients will develop a rapidly progressive infection with gas in the soft tissues that can resemble clostridial myonecrosis. Appropriate management consists of debridement of the affected area and administration of aminoglycoside, trimethoprim-sulfamethoxazole, or a third-generation cephalosporin. Eikenella corrodens is a facultative anaerobic gram-negative rod typically associated with human bite wounds. Penicillin or ampicillin is recommended for treatment. Histoplasma capsulatum is a fungus that results in arthralgia and arthritis in affected patients. Administration of amphotericin B is indicated. Pasteurella multocida is an anaerobic gram-negative bacillus, typically associated with cat bites and best treated with penicillin or amoxicillin with clavulanate. Staphylococcus aureus is an anaerobic gram-positive coccus present on the skin that is a frequent cause of skin and soft-tissue infections.

Answer 62

The correct response is Option C. The venom of the black widow spider (Latrodectus mactans) is a neurotoxic agent that causes the hallmark findings of muscle pain and cramping that appear within 15 minutes after the bite. This common species of spider is found throughout the United States. Most patients with latrodectism are bitten by female spiders; in contrast, the bite of the male spider rarely penetrates the skin. Affected patients have sharp pain at the wound site with two small red spots marking the location of puncture. Late findings include pain and cramping of the striated muscles, abdominal pain, vomiting, tremor, excessive salivation, and shock. In a patient who is bitten by a black widow spider, the most appropriate therapy is administration of 10 mL of 10% calcium gluconate solution over a period of 15 to 20 minutes; 1 ampule of methocarbamol or 5 mg to 10 mg of diazepam can be administered additionally. Improvement of the patient's symptoms following treatment is diagnostic of latrodectism. In immunocompromised patients, a diluted dose of black widow spider antivenin (Lyovac) should be administered intravenously at a slow rate. In contrast, the brown recluse spider produces a toxin known as sphingomyelinate, a dermonecrotic factor. Envenomation with sphingomyelinate results in hemolysis, coagulation, and platelet aggregation, often affecting fatty tissue. Symptoms can range from mild irritation to severe necrosis. Hemotoxins, such as cobra venom, are exotoxins that result in hemolysis.

Answer 63

The correct response is Option E. This patient has developed infection with Aeromonas hydrophila after undergoing leech therapy for five days. Medicinal leeches such as the Hirudo medicinalis species (which is the most commonly used leech and is endemic to Southeast Asia and Europe) can be applied to flaps or replanted limbs in order to relieve venous congestion. However, a common complication of leech therapy is the development of infectious organisms such as Aeromonas hydrophila, a gram-negative rod that can be detected in as many as 20% of persons within the first 10 days of therapy. Infiltration of Aeromonas hydrophila organisms can result in a rapidly progressive infection with gas in the soft tissues that can resemble clostridial myonecrosis. If infection does develop, trimethoprim-sulfamethoxazole is recommended for first-line therapy. Fluoroquinolones such as ciprofloxacin are also effective. Antibiotics that are still effective but less frequently recommended include antipseudomonal aminoglycoside, imipenem, meropenem, tetracycline, and second-, third-, or fourth-generation cephalosporins.

Answer 64

The correct response is Option E. This patient who has sustained a pit viper bite to the dominant right thumb requires immediate treatment involving fasciotomy, intravenous administration of antibiotics, and administration of pit viper antivenin. Approximately 98% of venomous snake bites are from pit vipers, and more than 70% of these bites involve the upper extremity. Pit vipers can be distinguished from other snakes by the presence of two retractable maxillae, each of which contains a fang for envenomation. In patients who sustain pit viper bites, immediate first aid should consist of patient reassurance, immobilization of the affected limb and placement of the limb on a level plane, and transportation to a hospital as soon as possible. Envenomation should be assumed with the presence of fang marks and rapid swelling of the extremity; broad-spectrum antibiotics should be administered immediately in the emergency department. Patients who have tense edema of the affected extremity and compartment pressures of greater than 30 mmHg should be diagnosed with compartment syndrome. Urgent fasciotomy should be performed. Because snake venom can greatly worsen myonecrosis and systemic findings, antivenin should be administered to any patient who has systemic symptoms of envenomation associated with increased laboratory values. Following administration of a test dose, five to 10 vials of snake antivenin are typically administered in patients who do not exhibit allergic sensitivity. A central line should be placed and emergency resuscitation should be available. The administration of as many as 20 vials of antivenin may be required in patients who have extreme abnormalities on laboratory evaluation. Application of ice will result in vasoconstriction, ischemia, and tissue necrosis. Incision and suction drainage of the bite wound should be performed within 15 minutes of the bite.

Answer 65

The correct response is Option A. In this patient who has a history of recurrent inflammation consistent with chronic paronychial infection, the most likely causal organism is Candida albicans, which has been shown to be responsible for as many as 97% of cases of chronic paronychia. In patients with this condition, the affected area should be kept dry and a topical antifungal agent such as clotrimazole should be applied. Eponychial marsupialization, which involves the removal of a crescent-shaped piece of skin from the eponychium, may be considered to clear the scarred, infected tissues. Herpes simplex virus results in herpetic whitlow, an extremely painful condition characterized by visible vesicles. It is self-limiting and typically resolves in three to four weeks, but may recur. Incision and drainage are not indicated. Mycobacterium marinum, an atypical mycobacterium, can result in superficial or deep granulomatous infections. The recommended treatment includes multidrug antituberculous therapy and surgical debulking. Although Pseudomonas aeruginosa is part of the normal flora of the hyponychial space, this organism can result in acute infection in patients with diabetes mellitus or can be a secondary cause of chronic paronychia. Discoloration of the nail is a frequent finding. Staphylococcus aureus is the predominant pathogen associated with acute paronychial infection, which manifests as an abscess requiring incision and drainage.

Answer 66

The correct response is Option E. Kanavel signs include pain on passive extension, flexed resting posture, tenderness along the flexor tendon sheath, and fusiform swelling. However, not all signs are present in flexor tenosynovitis, and even then it can be just one symptom. Dailiana et al found that only 54% of patients (22 out of 41) diagnosed with purulent flexor tenosynovitis had all four Kanavel signs. Kennedy and colleagues calculated positive predictive values (PPVs) of the four classic Kanavel signs, with the greatest PPV seen with tenderness to palpation over the flexor sheath, followed by pain with passive extension. Flexed posturing had the lowest PPV. Cellulitis is commonly seen around the finger, but having it spread to the dorsum of the hand is less common. Numbness and tingling and delayed capillary refill can both be late findings if flexor tenosynovitis remains untreated but are not specific to the diagnosis.

Answer 67

The correct response is Option B. Of those listed, the most appropriate pre- and intraoperative dosages of cefazolin for this patient is an initial intravenous dose of 2 g followed by redosing every 4 hours. According to current guidelines by the Centers for Disease Control and Prevention, dosing of prophylactic antimicrobials should be adjusted based on patient weight. Recommended doses for cefazolin are: * 30 mg/kg for pediatric patients * 1 g for adult patients with weight less than 176 lb (80 kg) * 2 g for adult patients with weight greater than or equal to 176 lb (80 kg) and less than 264.6 lb (120 kg) * 3 g for adult patients with weight greater than or equal to 264.6 lb (120 kg) Redosing of the antibiotic agent should occur at intervals of 2 half-lives, measured from the time of initial administration. Shorter redosing intervals should be considered when excessive blood loss occurs. Longer intervals should be considered for renal impairment. The half-life of cefazolin in adults with normal renal function is approximately 1.8 hours (mostly ranging from 1.2 to 2.2 hours).

Answer 68

The correct response is Option C. While antibiotic prophylaxis in orthopedic, cardiac, and other procedures is supported by robust scientific evidence, data to support routine use specifically in plastic surgery is lacking. There is a general consensus for administering an intravenous dose of prophylactic antibiotic in clean breast surgery to decrease the risk for postoperative surgical site infection. This should be given within 60 minutes prior to skin incision. The choice of antibiotic should cover skin flora, primarily gram-positive organisms such as Staphylococcus aureus, Streptococcus pyogenes, Cutibacterium acnes, diphtheroids, lactobacilli, and Bacillus spp. The first choice of antibiotic is typically a first-generation cephalosporin, such as cefazolin. However, this patient has a previous anaphylactic reaction to penicillin. While reported cross reactivity between cephalosporins and penicillins is only 1 to 10%, due to the severity of the prior reaction, cefazolin is not the best choice. When a first-generation cephalosporin is not an option due to allergy or another reason, then clindamycin, vancomycin, and fluoroquinolones represent other acceptable choices. The other antibiotic options are not as effective against skin flora and therefore are not the best choices. Ceftriaxone is a third-generation cephalosporin, which has broader gram-negative coverage but is worse against skin flora, including Staphylococcus aureus. Furthermore, the severe penicillin allergy argues against use of any cephalosporin. Gentamicin is much more effective against gram-negative organisms. Toxicity can affect renal function as well as the inner ear. Piperacillin is a synthetic penicillin which is often combined with the beta-lactamase inhibitor tazobactam, giving it a broader spectrum effect against both gram-positive and gram-negative organisms. It is commonly used for serious infections, such as pneumonia and peritonitis. However, severe hypersensitivity to penicillin for this patient precludes its recommended use.

Answer 69

The correct response is Option A. Honey has been used as a wound dressing since ancient Greece. It is known to stimulate the immune system, suppress inflammation, and cause rapid autolytic debridement. As such, it is an inexpensive and effective topical biologic treatment. There are a myriad of biologic properties responsible for this. Honey not only expedites the wound healing process itself but also has antimicrobial properties. This is a function of the hydrogen peroxide content; however, high concentrations of catalase can inactivate it. In manuka honey, specifically, the antimicrobial properties come from the methylglyoxal, which is not inactivated by the enzyme catalase. Methylglyoxal is able to alter the structure of the bacterial fimbriae and flagella, limiting bacterial adherence and motility. Thus a higher methylglyoxal concentration, such as is found in manuka honey, would be a more effective antimicrobial, not less. The low or acid pH (average 3.9) increases the release of oxygen from hemoglobin and makes the wound milieu less favorable for destructive proteases. The high osmolality of the honey functions to draw fluid out of the wound as well as create an outflow of lymph. The two main types of sugars in honey are fructose and glucose, but varying the concentration of either will not result in an increase in antimicrobial activity.

Answer 70

D Peripheral parenteral nutrition (PPN) and total parenteral nutrition (TPN) are hypertonic, osmotically active agents that cause an imbalance between intracellular and extracellular compartments, resulting in fluid shifts, cellular dysfunction, and injury. Hypotonicity of the substance is incorrect because PPN and TPN are hypertonic, not hypotonic. Extravasation of vasopressors, such as dobutamine or vasopressin, leads to direct local vasoconstriction, causing tissue ischemia and necrosis. Direct cytotoxicity of the infiltrated agent describes chemotherapeutic drugs such as vesicants (eg, doxorubicin) or exfoliants (eg, cisplatin). Some have advocated using local hyaluronidase to treat hypertonic and chemotherapeutic extravasations. Arterial leakage would manifest as a hematoma and compartment syndrome and is not directly related to PPN injury to soft tissue. Compartment muscles may be injured if fasciotomy is not performed emergently.

Answer 71

A The patient is presenting with a necrotizing fasciitis (type 2 monomicrobial) infection due to group A Streptococcus pyogenes. While this condition is rare following aesthetic surgery, the majority of reports are associated with liposuction, and the most common organism is Streptococcus pyogenes. The most appropriate treatment includes surgical debridement and antibiotic treatment with clindamycin and penicillin. Clindamycin suppresses streptococcal toxin and cytokine production, but its use as a monotherapy is not recommended initially due to the possibility of developing clindamycin resistance. It should, therefore, be used in combination with penicillin until antimicrobial sensitivities determine appropriate de-escalation. Other type 2 infections, due to a single micro-organism, are less common and include methicillin-resistant Staphylococcus, Aeromonas hydrophilia, and Vibrio vulnificus. Type 1 necrotizing fasciitis is polymicrobial in nature and can involve aerobic and anaerobic bacteria. Presence of gas gangrene in type 1 infections is often indicative of the presence of clostridial species. Treatment of type 1 infections initially involves the administration of vancomycin or linezolid with piperacillin-tazobactam, a carbapenem, ceftriaxone and metronidazole, or a fluoroquinolone and metronidazole, and then is de-escalated based on sensitivities. Vancomycin monotherapy is not indicated as an initial treatment for either type 1 or 2 necrotizing fasciitis.

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Soft Tissue Infection 01-20, 24 Flashcards

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