David M. Cline
The management of soft tissue infections in the ED involves an understanding of appropriate antibiotic treatment, outpatient or inpatient treatment options, and an understanding of when surgical intervention is necessary.
METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS
Community-acquired methicillin-resistant Staphy-lococcus aureus (MRSA) is epidemic across all populations.
A significant majority of soft tissue infections in adults and children are caused by community-acquired MRSA.
Understanding the treatment of community-acquired MRSA is vital for those managing soft tissue infections in the ED.
CLINICAL FEATURES
Lesions are typically warm, red, and tender, and may be draining a purulent fluid.
MRSA lesions are frequently mistaken as spider bites by patients as well as clinicians.
DIAGNOSIS AND DIFFERENTIAL
The diagnosis of MRSA is largely clinical.
Community-acquired MRSA should be considered in any infection where S. aureus or Streptococcus is typically considered the etiologic agent. This includes skin and soft tissue infections as well as sepsis and pneumonia.
Bedside ultrasound is helpful to identify abscess collections in equivocal cases (see Fig. 92-1).
FIG. 92-1. Typical appearance of a subcutaneous abscess on a thigh. The abscess cavity is rounded and hypoechoic with mixed internal echogenicity. There is posterior acoustic enhancement that reflects the liquid nature of the abscess contents. The surrounding skin is hyperechoic because of adjacent tissue edema and possibly cellulitis. (Reproduced with permission from Ma OJ, Mateer JR, Blaivas M: Emergency Ultrasound, 2nd ed. Copyright © The McGraw-Hill Companies, 2008. All rights reserved. Figure 16–89.)
EMERGENCY DEPARTMENT CARE AND DISPOSITION
For many community-acquired MRSA cutaneous infections, adequate incision and drainage is adequate to manage these infections. Suggested criteria for withholding antibiotics include abscesses that are small <5 cm, abscesses in immunocompetent patients, and abscesses without accompanying cellulitis.
If local epidemiology supports MRSA as the likely etiology of cellulitis, antibiotics effective against MRSA should be given. These include clindamycin 300 milligrams PO four times daily or trimethoprim/sulfamethoxazole double-strength 1 to 2 tablets twice a day for 7 to 10 days.
Consider adding cephalexin 500 milligrams four times daily to a regimen with trimethoprim/sulfam-ethoxazole to cover Streptococcus. If the infection is severe, vancomycin 1 gram every 12 hours should be used, and inpatient therapy is indicated.
Patients who are at the extremes of age and have fever, significant comorbidities, or a large number of lesions may require admission for parenteral antibiotics.
NECROTIZING SOFT TISSUE INFECTIONS
Necrotizing soft tissue infections are a spectrum of conditions that may be polymicrobial or monomicrobial.
Group A Streptococcus and S. aureus are often the etiologic agents in monomicrobial infections.
Clostridial infections are now uncommon due to improved hygiene and sanitation.
CLINICAL FEATURES
Patients present with pain out of proportion to physical findings and a sense of heaviness in the affected part.
Physical findings typically include a combination of edema, brownish skin discoloration, bullae, malodorous serosanguineous discharge, and crepitance.
The patient frequently has a low-grade fever and tachycardia out of proportion to the fever.
Mental status changes, including delirium and irritability, may accompany necrotizing soft tissue infections.
DIAGNOSIS AND DIFFERENTIAL
Familiarity with the disease and an appreciation of the subtle physical findings are the most important factors in making the diagnosis of necrotizing soft tissue infections.
Additional findings that may confirm the clinical suspicion include gas within soft tissue on plain radiographs, metabolic acidosis, coagulopathy, hyponatremia, leukocytosis, anemia, thrombocytopenia, myoglobinuria, and renal or hepatic dysfunction.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
The patient with necrotizing soft tissue infections should be adequately resuscitated with crystalloid intravenous (IV) fluids and packed red blood cells if there is significant hemolysis with anemia.
Urine output and central venous pressure readings should be used to assess volume status.
Vasoconstrictors should be avoided in these patients because of compromised perfusion in the affected extremity.
IV antibiotics should be administered, including vancomycin 1 gram IV every 12 hours plus meropenem 500 to 1000 milligrams IV every 8 hours. Alternatively, piperacillin/tazobactam 4.5 grams IV every 6 hours may be used. The use of clindamycin should also be considered as it inhibits toxin synthesis.
Tetanus prophylaxis should be administered as indicated.
Surgical consultation for debridement should be obtained immediately and may include fasciotomy or amputation.
Hyperbaric oxygen therapy and IV immunoglobulin therapy are controversial and typically the decision of the treating surgeon.
CELLULITIS
Cellulitis is a local soft tissue inflammatory response secondary to bacterial invasion of the skin.
Cellulitis is more common in the elderly, immuno-compromised patients, and patients with peripheral vascular disease.
CLINICAL FEATURES
Cellulitis presents as localized tenderness, erythema, and induration.
Lymphangitis and lymphadenitis may accompany cellulitis and indicate a more severe infection.
Patients may have fever and chills but are infrequently bacteremic.
DIAGNOSIS AND DIFFERENTIAL
The clinical presentation is usually sufficient for diagnosis.
Obtaining a white cell count or blood cultures rarely changes management of otherwise healthy patients with simple cellulitis.
The differential diagnosis includes any erythematous skin condition. Cellulitis of the lower extremity is sometimes complicated by deep venous thrombosis and may require venogram or Doppler studies for a complete evaluation.
In patients with systemic toxicity (fever and leukocytosis), cultures of pus, bullae, or blood should be obtained.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Simple cellulitis in which MRSA is not suspected can be treated in an outpatient setting using cephalexin 500 milligrams PO four times daily, dicloxacillin 500 milligrams PO four times daily, or clindamycin 300 milligrams four time daily.
If local epidemiology supports a high likelihood of MRSA in patients with soft tissue infections, antibiotics effective against MRSA should be given. In these cases clindamycin, trimethoprim/sulfamethoxazole, or doxycycline ± cephalexin should be given (see treatment of MRSA in the first section of this chapter).
All patients discharged should have close follow-up within 2 to 3 days to evaluate the cellulitis and response to therapy.
Skin markers may be helpful to mark the extent of cellulitis in patients discharged from the ED.
All patients with systemic toxicity or evidence of bac-teremia should be admitted to the hospital. Patients with diabetes mellitus, alcoholism, or other immuno-suppressive disorders should be considered for admission for IV antibiotics.
IV antibiotics, such as clindamycin, vancomycin, or linezolid, should be used in patients requiring hospital admission.
ERYSIPELAS
Erysipelas is a superficial cellulitis with lymphatic involvement caused primarily by group A Streptococcus. Infection is usually through a portal of entry in the skin.
CLINICAL FEATURES
Onset is acute, with sudden high fever, chills, malaise, and nausea.
Over the next 1 to 2 days, a small area of erythema with a burning sensation develops.
FIG. 92-2. Butterfly rash of erysipelas. The sharp demarcation between the salmon-red erythema and the normal surrounding skin is evident. (Reproduced with permission from Shah BR, Lucchesi M: Atlas of Pediatric Emergency Medicine, © 2006, McGraw-Hill, New York.)
The erythema is sharply demarcated from the surrounding skin and is tense and painful (see Fig. 92-2).
Lymphangitis and lymphadenitis are common.
Purpura, bullae, and necrosis may accompany the erythema.
It is primarily an infection of the lower extremities.
DIAGNOSIS AND DIFFERENTIAL
The diagnosis is based primarily on physical findings.
Leukocytosis is common.
Cultures, Antistreptolysin O (ASO) titers, and anti-DNAase B titers are of little use in the ED. Differential diagnosis includes other forms of local cellulitis.
Some believe necrotizing fasciitis is a complication of erysipelas and should be considered in all cases.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Treatment is with parenteral antibiotics active against streptococci, including ceftriaxone 1 gram every 24 hours or cefazolin 1 to 2 grams every 8 hours.
If it is difficult to distinguish between cellulitis and erysipelas, cover for S. aureus as well as streptococci (see above).
If the disease is severe, treat for MRSA with van-comycin, clindamycin, or linezolid and admit to the hospital.
Patients with mild disease may be treated with an initial dose of parenteral antibiotics and discharged on penicillin 500 milligrams PO every 6 hours.
If the patient is allergic to penicillin, a macrolide or cephalosporin may be used.
Duration of treatment is 5 to 10 days, and these patients should be re-evaluated in 2 days for follow-up.
CUTANEOUS ABSCESSES
Cutaneous abscesses are the result of a breakdown in the cutaneous barrier, with subsequent contamination with resident bacterial flora. Incision and drainage is usually the only necessary treatment.
CLINICAL FEATURES AND DIAGNOSIS
Patients present with an area of swelling, tenderness, and overlying erythema.
The area of swelling is frequently fluctuant.
Cutaneous abscesses are usually localized, although they may cause systemic toxicity in the immunosuppressed.
Cutaneous abscesses should be inspected closely for predisposing injury and foreign bodies.
Radiography may be indicated if foreign body is suspected.
Needle aspiration or ultrasound may aid in the diagnosis when it is unclear whether the patient has an abscess or cellulitis (see Fig. 92-1).
EMERGENCY DEPARTMENT CARE AND DISPOSITION
See Chapter 9 for information on procedural sedation.
BARTHOLIN GLAND ABSCESS
Bartholin gland abscess presents as unilateral painful swelling of the labia with a fluctuant 1- to 2-cm mass.
These infections are typically polymicrobial but may contain Neisseria gonorrhoeae and Chlamydia trachomatis.
Routine antimicrobial treatment is not necessary unless there is a suspicion of sexually transmitted disease.
Treatment involves incision and drainage along the vaginal mucosal surface of the abscess, generally followed by the insertion of a Word catheter.
The Word catheter can be left in place for up to 4 weeks. Sitz baths are recommended after 2 days.
Follow-up with gynecology is recommended within 2 days in patients with severe symptoms and within 1 week in patients with mild symptoms.
HIDRADENITIS SUPPURATIVA
Hidradenitis suppurativa is a recurrent chronic infection involving the apocrine sweat glands.
These abscesses tend to occur in the axilla and in the groin. The causative organism is usually Staphylococcus, although Streptococcus also may be present.
The abscesses are typically multiple and in different stages of progression.
ED treatment involves incision and drainage of any acute abscess, treating with antibiotics for any cellulitis that may be present, and referral to a surgeon for definitive treatment.
INFECTED SEBACEOUS CYSTS
Infected sebaceous cysts may develop in the sebaceous glands, which occur diffusely throughout the skin.
Cysts present with an erythematous, tender, cutaneous mass that is often fluctuant.
Incision and drainage is the appropriate ED treatment, with wound rechecks in 2 to 3 days in the ED or physician’s office.
The cyst contains a capsule that must be removed to prevent recurrence. This capsule can sometimes be grasped at the time of the initial incision and drainage; however, this is typically done at a later follow-up visit.
PILONIDAL ABSCESS
Pilonidal abscess presents as a tender, swollen, and fluctuant mass along the superior gluteal fold.
Treatment includes incision and drainage followed by iodoform gauze packing.
The patient should be rechecked in 2 to 3 days, and the wound should be repacked.
Surgical referral is usually necessary for definitive treatment.
Antibiotics are not necessary unless there is an accompanying cellulitis.
FOLLICULITIS AND CARBUNCLES
Staphylococcal soft tissue infection may cause fol-liculitis; the inflammation of a hair follicle is caused by bacterial invasion, and is usually treated with warm compresses.
When deeper invasion occurs, the soft tissue surrounding the hair follicle becomes infected, and a furuncle (boil) is formed.
Warm compresses are usually adequate to promote spontaneous drainage.
If several furuncles coalesce, they may form a large area of interconnected sinus tracts and abscesses called a carbuncle.
Carbuncles usually require surgical referral for wide excision.
In the healthy, immunocompetent patient, routine use of antibiotics following abscess incision and drainage is not indicated unless there is a secondary infection.
In the potentially immunocompromised patient, the threshold for antibiotic use should be lowered.
Patients presenting with secondary cellulitis or systemic symptoms should be considered for antibiotic therapy.
Abscesses involving the hands and face also should be treated more aggressively with antibiotics.
Prophylaxis for endocarditis in patients with structural cardiac abnormalities should be considered (see Chapter 95 for information on those at risk).
SPOROTRICHOSIS
Sporotrichosis is caused by traumatic inoculation of the fungus Sporothrix schenckii, which is found on plants and in the soil.
CLINICAL FEATURES
After a 3-week incubation period, three types of infection may occur.
The fixed cutaneous type occurs at the site of inoculation and looks like a crusted ulcer or verrucous plaque.
The local cutaneous type also remains at the site of inoculation but presents as a subcutaneous nodule or pustule. The surrounding skin may become ery-thematous.
The lymphocutaneous type is the most common of the three. It presents as a painless nodule at the site of inoculation that develops subcutaneous nodules that migrate along lymphatic channels.
DIAGNOSIS AND DIFFERENTIAL
The diagnosis is based on the history and physical examination.
Tissue biopsy cultures are often diagnostic but of limited use in the ED.
The differential diagnosis includes tuberculosis, tularemia, cat-scratch disease, leishmaniasis, nocardiosis, and staphylococcal lymphangitis.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Itraconazole 100 to 200 milligrams/d PO for 3 to 6 months is highly effective when treating sporotrichosis.
If disseminated, sporotrichosis may be treated with IV amphotericin B 0.5 milligram/kg/d (after test doses to determine tolerability).
Most cases of cutaneous sporotrichosis can be treated on an outpatient basis.
Those patients who have systemic symptoms or who are acutely ill should be admitted for possible treatment with amphotericin B.
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 147, “Soft Tissue Infections,” by Elizabeth W. Kelly and David Magilner.