SKIN AND SOFT-TISSUE INFECTIONS (SSTIs) represent a diverse group of infections that vary in clinical presentation and degree of severity. They are one of the most common infections in both the community and hospital settings and account for nearly 4.8 million emergency department (ED) visits annually (Amin et al., 2014; Pallin et al., 2008; Pollack et al., 2015; Rui, Kang, & Ashman, 2016). Rui et al. (2016) indicated that 3.5% of all ED visits are for SSTIs, and the Agency for Healthcare Research and Quality (Moore, Stocks, & Owen, 2017) assert that SSTIs are the fifth most common medical complaint for ED patients in the United States.
There is a range of SSTIs and distinguishing one infection from another leads to appropriate treatment and management. For this reason, it is essential for all emergency care providers, including advanced practice nurses (APRNs), to have a comprehensive understanding of the physical examination findings, clinical practice guidelines, diagnostics, and management. This article reviews the definition, clinical presentation, and management for abscesses, cellulitis, and necrotizing fasciitis and presents a common case study for consideration.
BACKGROUND AND SIGNIFICANCE
Infections of the skin and soft tissue are encountered in community and health care settings and may commonly result in ED visits. The overall incidence of SSTIs has steadily increased over the last few decades. In fact, according to the National Hospital Ambulatory Medical Care Survey (Rui et al., 2016), U.S. ED visits for SSTIs increased from 1.2 million in 1993 to 3.4 million in 2005, whereas hospitalizations for SSTIs have increased similarly (Edelsberg et al., 2009; Pallin et al., 2008; Talan et al., 2015). This dramatic increase coincides with the emergence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) and can be attributed to the increase in incidence of SSTIs, in particular cellulitis and abscesses. These common clinical condition infections can have mild to potentially life-threatening clinical outcomes and complications. Therefore, it is prudent to understand the intricacies of disease recognition, treatment, and management.
CLINICAL FEATURES AND ASSESSMENT
Skin and soft-tissue infections represent a collection of diagnoses that are reflective of an inflammatory microbial invasion of the epidermis, dermis, and subcutaneous tissues (Dryden, 2009). When the skin barrier is compromised, pathogens can cause infections as they gain access from a break in the skin, ulcer, burn, or trauma/surgical wounds (Dryden, 2009). The vast majority of SSTIs are commonly managed on an outpatient basis. However, some cases require hospitalization for parenteral antibiotic coverage and surgical management.
Cellulitis is a potentially serious SSTI that may spread to the blood and lymphatic systems, causing a potentially life-threatening situation. It is characterized by erythematous areas of skin that are edematous, indurated, and poorly demarcated (see Table 1). The area may be tender and warm but not fluctuant (see Figure 1).
Table 1. -
Skin and soft-tissue infections
||A collection of pus within the dermis or deeper that is accompanied by edema, redness, and/or induration
||Erythematous, fluctuant, and tender area within the dermis and deeper tissues
||Anechoic or hypoechoic oblong or spherical collection of echogenic fluid representative of a purulent collection
Streptococcus pyogenes and Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus
||A diffuse skin infection characterized by areas of erythema, edema, or induration
||Erythematous, indurated, and tender area to the skin that is superficial
||Increased echogenicity with progression to hyperechoic fat lobules that are separated by hyperechoic fluid-filled areas producing a cobblestone appearance
Streptococcus species, Staphylococcus aureus, dog bite—Pasteurella multocida, human bite—Eikenella corrodens, salt water exposure—Vibrio vulnificus
||Skin infection characterized by rapid destruction of tissue and system toxicity
||Constitutional symptoms: fever, tachycardia, AMS, DKA, with/without evidence of skin inflammation
Skin changes: Patchy discoloration and swelling
Progressive disease: Development of tense edematous tissue, grayish-brown “dishwater” discharge, bullae, necrosis, and crepitus
|Positive subcutaneous thickening, air, and fascial fluid (STAFF)
Staphylococcus aureus, Streptococcus pyogenes, and enterococci; Escherichia coli and Pseudomonas species; and anaerobic organisms, such as Bacteroides or Clostridium
Abscesses are characterized by purulent drainage from an erythematous wound that is indurated and/or edematous. This collection of pus is within the dermis or deeper and is accompanied by redness, edema, and induration (Center for Drug Evaluation and Research, Food and Drug Administration, United States Department of Health and Human Services [HHS], 2013; see Figure 2). Common bacterial pathogens causing SSTIs are Streptococcus pyogenes and Staphylococcus aureus including MRSA (see Table 1). Less common causes include other Streptococcus species, Enterococcus faecalis, Klebsiella pneumoniae, or gram-negative bacteria (Center for Drug Evaluation and Research, Food and Drug Administration, HHS, 2013; Talan et al., 2011; Yadav, Gatien, Corrales-Medina, & Stiell, 2017).
Cellulitis and abscesses are the most common SSTIs in the community and hospital settings. Ray, Suaya, and Baxter (2013) examined the incidence, microbiology, and patient characteristics of SSTIs from patients enrolled in the Kaiser Permanente program in Northern California and noted that 376,262 individuals experienced 471,550 SSTIs over a 2-year time period. Of those who had a culture performed, Staphylococcus aureus was isolated in 81% of the specimens, of which 46% were MRSA.
Necrotizing Soft-Tissue Infections
Necrotizing soft-tissue infections span a spectrum of diseases characterized by high mortality rates, extensive soft-tissue necrosis, and systemic toxicity (Kelly & Magilner, 2016). Terms utilized to describe necrotizing soft-tissue infections include “necrotizing fasciitis,” “Fournier's gangrene,” or “gas gangrene.” The rapid necrotizing process commences with a direct invasion of subcutaneous tissue from external trauma, including intravenous injection, abscess, insect bite) or direct spread from a perforated viscus. The bacteria will proliferate with invasion into the subcutaneous tissue and deep fascia. Ultimately, exotoxin release leads to tissue ischemia, liquefaction necrosis, and systemic toxicity (Kelly & Magilner, 2016). Classic symptoms of necrotizing soft-tissue infections include severe pain, diaphoresis, and anxiety. Physical examination oftentimes reveals cutaneous inflammation, edema, discoloration, and induration of the subcutaneous tissues that is wooden-hard (see Table 1). With necrotizing fasciitis, the underlying tissues are firm and the fascial planes and various muscle groups are undiscernible (Stevens et al., 2014). These deep infections are potentially devastating due to major tissue destruction that ultimately leads to death (Stevens et al., 2014).
CLINICAL PRACTICE GUIDELINES
The Infectious Disease Society of America (IDSA) established practice guidelines for the diagnosis and management of SSTIs. These recommendations focus on the diagnosis and treatment of all SSTIs from minor infections, for example, impetigo, to life-threatening infections such as necrotizing fasciitis (Liu et al., 2011; Stevens et al., 2014). The guidelines facilitate prompt diagnosis, identification of pathogen, and efficient treatment.
According to the IDSA guidelines, the recommended treatment of an abscess is an incision and drainage. Gram stain and culture of pus from abscesses are recommended, but treatment without obtaining these studies is reasonable. The utilization of antibiotics in addition to the incision and drainage is recommended with the presence of systemic inflammatory response syndrome (SIRS), including a temperature of more than 38 °C or less than 36 °C, tachypnea, tachycardia, a white blood cell count of more than 12,000 or fewer than 400 cells/μL, or evidence of failed initial outpatient treatment (Miller et al., 2015; Stevens et al., 2014).
Cellulitis without signs of systemic illness in the general population should be treated with an antimicrobial agent that is active against streptococci. Parenteral antibiotics are indicated in patients who do present with systemic symptoms. For patients who present with a history of MRSA, penetrating trauma, including intravenous drug use, or SIRS, antimicrobial treatment against MRSA is recommended in addition to the coverage for streptococci (Stevens et al., 2014). Broad-spectrum coverage may be considered in patients who are immunocompromised. Cultures are not routinely recommended unless the patient is neutropenic, has severe cell-mediated immunodeficiency, has a malignancy and is undergoing chemotherapy, has failed outpatient treatment and taking another agent, or has sustained an animal bite (Stevens et al., 2014). In addition to pharmacological management, elevation of the affected extremity is indicated.
Outpatient therapy for SSTIs is recommended for all patients who do not have SIRS, hemodynamic instability, or an altered mental state, whereas hospitalization is recommended if the infection is severe, if there is concern for a deeper infection or necrotizing fasciitis, if the patient is failing outpatient treatment, or if there is a concern for poor adherence to therapy (Cranendonk, Lavrijsen, Prins, & Wiersinga, 2017; Gunderson, Cherry, & Fisher, 2018; Kamath et al., 2018; Stevens et al., 2014).
Necrotizing Fasciitis Management
Prompt surgical consultation is recommended for patients with aggressive infections, including necrotizing fasciitis. Empirical antibiotic treatment should include broad coverage (i.e., vancomycin or linezolid plus piperacillin-tazobactam or a carbapenem; plus ceftriaxone and metronidazole; Stevens et al., 2014). Early recognition is key with necrotizing infections as time is of the essence. In fact, necrotizing soft-tissue infections can spread as fast as 1 inch per hour. Surgery is considered the gold standard for diagnosis and treatment and may include fasciotomy, debridement, or amputation (Kelly & Magilner, 2016).
Community-Associated Methicillin-Resistant Staphylococcus aureus
Staphlococcus aureus is a major cause of both purulent and nonpurulent SSTIs (Moran, Gorwitz, & McDougal, 2006; Stevens et al., 2014). Methicillin-resistant Staphylococcus aureus is associated with health care infections, as well as community-associated infection. Since the early 1900s, there has been a steady increase in incidence of the disease from 1.2 million ED visits to 3.4 million ED visits in just 10 years (Pallin et al., 2008; Rui et al., 2016). This influx of disease has contributed to a notable public health problem and has resulted in an increase in invasive infections nationwide among patients seeking treatment in the ED (Edelsberg et al., 2009; Pollack et al., 2015). For patients with cutaneous abscess, the primary treatment is an incision and drainage alone. Per the clinical practice guidelines for the treatment of MRSA from the IDSA, antibiotic therapy is indicated for patients with the following:
- Signs and symptoms of systemic illness;
- Severe or extensive disease, including infections with multiple sites;
- History suggestive of a rapid progression with associated cellulitis;
- Abscess in a high-risk and complicated area to drain, including the face, genitalia, and hands/feet;
- Associated septic phlebitis;
- Extremes of age from the very young to the very old; and
- Failure to respond to incision and drainage alone. (Liu et al., 2011)
Patients who have purulent cellulitis should receive empirical coverage for CA-MRSA. In contrast, those who have nonpurulent cellulitis should receive empirical therapy for infection due to β-hemolytic streptococci. Only patients who do not respond to treatment of nonpurulent cellulitis with a β-lactam should receive empirical coverage for CA-MRSA (Liu et al., 2011). Hospitalized patients with a complicated SSTI, including those that involve major abscesses, infected burns or ulcers, deeper soft tissue, and surgical/traumatic wounds, should be treated with surgical debridement and broad-spectrum antibiotics with consideration for empirical therapy for MRSA. Wound cultures should be obtained from patients who present with systemic illness, patients who have failed initial treatment, or patients with severe infection (Liu et al., 2011; Moran et al., 2006; Singer & Talan, 2014).
A 28-year-old homeless man presented to the ED with a 2-day history of left lower extremity pain. The patient was well known to the ED for frequent visits related to chronic methamphetamine use, multiple abscesses, and cellulitis. The patient had been evaluated 2 days earlier at a sister hospital for an incision and drainage of a right lower extremity abscess related to intravenous drug use and skin popping. No antibiotics were prescribed at that time. The patient presented to this ED with increased pain to his left leg and was under the influence of methamphetamine. Clinical findings included initial vital signs revealed an afebrile (37.6 °C), mildly hypertensive (148/78) patient with tachycardia (128 beats per minute) and mild tachypnea (22 breaths per minute). On physical examination, the patient was mildly somnolent but when prompted would answer questions appropriately. The bilateral lower extremities of the patient revealed chronic skin changes related to SSTIs secondary to drug use, with various hyperpigmented areas and numerous scars (see Figure 3). No crepitus or fluctuance was appreciated. A bedside ultrasound scan was performed, which revealed subcutaneous thickening, air, and fascial fluid (STAFF) (Castleberg, Jenson, & Dinh, 2014). The surgeon was immediately consulted, and the patient received intravenous antibiotics perioperatively.
Point-of-care ultrasound (POCUS) has proven to be a valuable tool for emergency providers to help guide the diagnosis of many disorders in the ED, including SSTIs (Comer, 2018). The utilization of POCUS can help the clinician differentiate between cellulitis, abscess, and even necrotizing fasciitis and will guide clinical management of these cases. It serves as an adjunct to assist in early diagnosis of each disorder as the presentations of abscess, cellulitis, and necrotizing fasciitis have distinct characteristics via ultrasound (Thom & Warlaumont, 2016; see Table 1).
The case previously discussed presented a commonly seen ED patient and certainly one who may have been overlooked. The patient was a high-risk frequent ED user who was under the influence of multiple substances. His altered mental state may have easily been attributed to drug utilization, though the true cause was likely related to the systemic toxicity secondary to the necrotizing skin infection. Ultimately, the identification of irregularly thickened fascia with fluid tracking along deep fascial planes aided in the clinical diagnosis of necrotizing fasciitis and was an invaluable tool that contributed to the expeditious care for this patient.
Skin and soft-tissue infection is one of the most common complaints in the ED. As emergency medicine providers, APRNs are aware that early recognition and diagnosis of the disease are key with SSTIs. These infections can vary in presentation, treatment, management, and potential for complication. Health care providers play an important role in mitigating these variances in care through the implementation and adherence to national guidelines that address not only the physical examination findings and treatment of the patient but also the sociodemographic characteristics of the patient that may predispose him or her to a higher risk of complication and poor health outcomes. In combination with the guidelines, POCUS is an invaluable tool and asset to emergency clinicians as it will allow for an expeditious evaluation of the disease with ultimate guidance of clinical management.
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