Skin and soft tissue infections

In the structure of surgical diseases, 35-45% are due to surgical infection - post-traumatic and postoperative wounds, acute and chronic purulent diseases, the development of hospital (nosocomial) infection of the skin and soft tissues.

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Causes of Skin and Soft Tissue Infections

The following reasons are identified:

• surgical infection (aerobic, anaerobic) of soft tissues,
• soft tissue injury complicated by purulent infection,
• soft tissue crush syndrome,
• hospital-acquired soft tissue infection.

Intensive therapy is indicated for extensive soft tissue infection lesions, which is typical for crush syndrome and the development of anaerobic non-clostridial soft tissue infection.

Long-term intensive care is associated with a high risk of developing a hospital infection.

Hospital (nosocomial) infection - development of skin infection after diagnostic and therapeutic measures. Hospital infection may be associated with laparoscopy, bronchoscopy, long-term artificial ventilation and tracheostomy, postoperative purulent complications, including those associated with the use of alloplastic materials (endoprosthetics), drainage of the abdominal or thoracic cavity and other causes. Skin and soft tissue infection may also be associated with violations of aseptic rules during therapeutic measures (post-injection abscesses and phlegmons, suppuration of soft tissues during catheterization of central veins).

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Central venous catheter-associated infection

Central venous catheterization-associated infection is one of the complications (hospital infection) associated with intensive care. Tunnel infection is the development of soft tissue infection over a distance of 2 cm or more from the puncture site and insertion of the catheter into the central vein.

Clinical symptoms in the area of catheter implantation are hyperemia, infiltration and suppuration or necrosis of soft tissues, pain on palpation. Catheter-associated complications are associated with violations of aseptic rules and the formation of an infected biofilm. The biofilm is formed from deposits of blood plasma proteins on the catheter surface. Most microorganisms, especially S. aureus and Candida albicans, have a non-specific adhesion mechanism, which leads to the formation of a microbial biofilm.

Clinical characteristics of skin and soft tissue infection

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Soft tissue status (inflammation, infiltration, viability)

Extensive (more than 200 cm2 ⁾ purulent wounds of soft tissues are one of the common variants of the development of surgical infection after extensive injuries and postoperative complications.

Determination of the wound surface area. Measurement formula:

S = (L - 4) x K - C,

Where S is the wound area, L is the wound perimeter (cm) measured with a curvimeter, K is the regression coefficient (for wounds approaching a square in shape = 1.013, for wounds with irregular contours = 0.62), C is a constant (for wounds approaching a square in shape = 1.29, for wounds with irregular contours = 1.016). The area of human skin is about 17 thousand ^cm2.

Damage to anatomical structures

The involvement of anatomical structures in the process depends on the causes of infection (trauma, postoperative complications, crush syndrome, etc.) and the type of pathogenic microflora. Aerobic microflora affects the skin and subcutaneous tissue (ICD 10 code - L 08 8).

The development of anaerobic non-clostridial infection is accompanied by damage to deep anatomical structures - subcutaneous tissue, fascia and tendons, muscle tissue. The skin is not significantly involved in the infectious process.

Crush syndrome is a common cause of acute ischemia and microcirculatory failure, resulting in severe soft tissue damage, usually due to anaerobic non-clostridial infection.

Non-clostridial phlegmon

Optimal conditions for the development of non-clostridial phlegmon are closed fascial sheaths with muscles, lack of contact with the external environment, and a lack of aeration and oxygenation. As a rule, the skin over the affected area is little changed.

The clinical characteristics of an infectious lesion of soft tissues depend on the localization of the infection:

• Cellulitis (ICD 10 code - L08 8) is a lesion of the subcutaneous fatty tissue caused by anaerobic non-clostridial infection.
• Fasciitis (ICD 10 code - M72 5) is an infectious lesion (necrosis) of the fascia.
• Myositis (ICD 10 code - M63 0) is an infectious lesion of muscle tissue.

Combined lesions of soft tissue microflora predominate, spreading far beyond the primary focus ("creeping" infection). Relatively small changes in the skin do not reflect the extent and volume of damage to soft tissue by the infectious process.

Clinical symptoms include skin edema, hyperthermia (38-39 °C), leukocytosis, anemia, severe intoxication, multiple sclerosis, and impaired consciousness.

Composition of microflora (main pathogens)

The species characteristics and frequency of identification of microflora depend on the causes of infection development.

• Angiogenic, including catheter-associated, infections with coagulase-negative staphylococci - 38.7%,
  • S. aureus - 11.5%,
  • Enterococcus spp -11.3%,
  • Candida albicans - 6.1%, etc.
• Postoperative purulent complications
  • coagulase-negative staphylococci - 11.7%,
  • Enterococcus spp -17.1%,
  • P. aeruginosa - 9.6%,
  • S. aureus - 8.8%,
  • E. coli - 8.5%,
  • Enterobacter spp - 8.4%, etc.

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Anaerobic non-clostridial soft tissue infection

Non-clostridial anaerobes are representatives of normal human microflora and are considered opportunistic pathogens. However, under appropriate clinical conditions (severe trauma, tissue ischemia, development of soft tissue infection in the postoperative period, etc.), anaerobic non-clostridial infection causes severe and extensive tissue infection.

The microbial profile includes an association of non-clostridial anaerobes, aerobic and facultative anaerobic microorganisms.

The main pathogens of anaerobic non-clostridial infections are the following types:

• gram-negative rods - B. fragilis, Prevotella melaninogemca, Fusobacterium spp,
• gram-positive cocci - Peptococcus spp., Peptostreptococcus spp.,
• gram-positive non-spore-forming rods - Actinomyces spp., Eubactenum spp., Propionibacterium spp., Arachnia spp., Bifidobacterium spp.,
• gram-negative cocci - Veillonella spp.

The causative agents of anaerobic non-clostridial infections can be gram-positive cocci - 72% and bacteria of the genus Bacteroides - 53%, less often gram-positive non-spore-forming rods - 19%.

Aerobic microflora in association with anaerobic non-clostridial infection is represented by gram-negative bacteria of the Enterobactenaceae family: E. coli - 71%, Proteus spp. - 43%, Enterobacter spp. - 29%.

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Stages of wound infection

• 1st phase - purulent wound. The inflammatory reaction of tissues to damaging factors (hyperemia, edema, pain) prevails, purulent discharge is characteristic, associated with the development of the corresponding microflora in the soft tissues of the wound.
• 2nd phase - regeneration phase. Microbial invasion decreases (less than 10 ³ microbes in 1 g of tissue), the number of young connective tissue cells increases. Reparative processes accelerate in the wound.

Postoperative complications

The incidence of postoperative infectious complications depends on the area and conditions of the surgical intervention:

• Planned operations on the heart, aorta, arteries and veins (without signs of inflammation), plastic surgery on soft tissues, joint replacement (infectious complications) - 5%.
• Operations (aseptic conditions) on the gastrointestinal tract, urinary system, lungs, gynecological operations - 7-10% infectious complications.
• Operations (inflammatory and infectious conditions) on the gastrointestinal tract, urinary system and gynecological operations - 12-20% of purulent complications.
• Operations in conditions of an ongoing infectious process on the organs of the cardiovascular system, gastrointestinal tract, genitourinary system, musculoskeletal system, soft tissues - more than 20% complications.

Diagnosis of skin and soft tissue infections

Ultrasound - determination of the condition of soft tissues (infiltration) and the spread of the infectious process (leakage).

CT and MRI - determination of pathologically altered, infected tissues. Cytological and histological examination of wound surface tissues. Allows to determine the phase of the wound process and indications for plastic closure of wound surfaces.

Bacteriological examination - bacterioscopy, wound microflora culture. The studies are carried out dynamically, which allows determining the type of pathogenic microflora, sensitivity to antibacterial drugs, indications for repeated surgical interventions and plastic surgeries.

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Treatment of skin and soft tissue infections

Intensive therapy of patients with extensive infectious lesions of soft tissues is carried out against the background of radical surgical treatment.

Surgical tactics for soft tissue infection include radical excision of all non-viable tissues with revision of adjacent soft tissues. Soft tissues in anaerobic infections are saturated with serous turbid discharge. Surgical intervention results in the formation of an extensive postoperative wound surface and the need for daily traumatic dressings under anesthesia with monitoring of the condition of soft tissues.

Infection of a large soft tissue mass (several anatomical structures) is accompanied by general manifestations of SIRS, as a result of biologically active substances entering the blood from damaged tissues, and the development of sepsis. Clinical symptoms include skin edema, hyperthermia (38-39 °C), leukocytosis, anemia, clinical symptoms of severe sepsis (dysfunction or failure of internal organs, severe intoxication, impaired consciousness).

Antibacterial therapy

The clinical diagnosis of anaerobic non-clostridial soft tissue infection involves the association of aerobic and anaerobic microflora and requires the use of broad-spectrum drugs. Early initiation of empirical antibacterial therapy should be carried out with drugs from the carbapenem group (imipenem, meropenem 3 g/day) or sulperazone 2-3 g/day.

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Correction of antibacterial therapy

Prescription of drugs according to sensitivity - is carried out after 3-5 days based on the results of bacteriological cultures of microflora. Under the control of repeated bacteriological cultures, the following are prescribed (aerobic microflora):

• amoxicillin/clavulanic acid 1.2 g three times daily, intravenously,
• cephalosporins III-IV generation - cefepime 1-2 g twice a day, intravenously,
• cefoperazone 2 g twice daily, intravenously,
• amikacin 500 mg 2-3 times a day

Taking into account the dynamics of the wound process, it is possible to switch to fluoroquinolones in combination with metronidazole (1.5 g) or clindamycin (900-1200 mg) per day.

Antibacterial therapy is carried out in combination with antifungal drugs (ketoconazole or fluconazole). Sowing fungi from sputum, blood is an indication for intravenous infusion of fluconazole or amphotericin B.

Adequacy control - repeated bacteriological cultures, i.e. qualitative and quantitative determination of microflora in infected soft tissues.

Infusion therapy [50-70 ml/(kg x day)] is necessary to correct water-electrolyte losses in case of extensive soft tissue infection, and also depends on the area of the wound surface. Colloidal, crystalloid, and electrolyte solutions are prescribed.

Adequacy control - peripheral hemodynamic parameters, central venous pressure level, hourly and daily diuresis.

Correction of anemia, hypoproteinemia and blood coagulation disorders (as indicated) - red blood cell mass, albumin, fresh frozen and supernatant plasma.

Control - clinical and biochemical blood tests, coagulogram. Detoxification therapy is carried out using GF, UV, plasmapheresis methods (as indicated).

Adequacy control - qualitative and quantitative determination of toxic metabolites by gas-liquid chromatography and mass spectrometry, assessment of neurological status (Glasgow scale).

Immunocorrection (secondary immunodeficiency) - replacement therapy with immunoglobulins.

Control - determination of the dynamics of cellular and humoral immunity indicators.

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Enteral and parenteral nutrition

Correction of protein-energy losses is an absolutely necessary component of intensive care in case of extensive soft tissue infection. Early initiation of nutritional support is indicated.

The level of protein-energy and water-electrolyte losses depends not only on the catabolic phase of metabolism, hyperthermia, increased nitrogen losses through the kidneys, but also on the duration of the purulent infection and the area of the wound surface.

An extensive wound surface in the 1st phase of the wound healing process leads to additional nitrogen losses of 0.3 g, i.e. about 2 g of protein per 100 ^cm2.

Long-term underestimation of protein-energy losses leads to the development of nutritional deficiencies and wound wasting.

Development of nutritional deficiency in patients with surgical infection

Duration of infection, days	Moderate nutritional deficiency (body mass deficit 15%)	Severe malnutrition (body weight deficit more than 20%)
Less than 30 days (% of patients)	31%	6%
30-60 days (% of patients)	67%	17%
More than 60 days (% of patients)	30%	58%

Monitoring the effectiveness of therapeutic nutrition - nitrogen balance level, concentration of total protein and albumin in plasma, body weight dynamics.

Thus, extensive infections of the skin and soft tissues, especially in the development of anaerobic non-clostridial infection or nosocomial (hospital) infection, require multicomponent and long-term intensive therapy.

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