Assessment of Infection in Burn Injuries

Introduction

Burn injuries place a severe economic burden on healthcare infrastructure worldwide. They are also associated with high mortality due to serious complications. Infection is the most common complication of burns. Therefore, timely and accurate diagnosis is crucial Prevent harmful outcomes and optimize healing outcomes for this patient population. [1]

There are several reasons for the increased risk of burn wound infection: (1) the body’s physiological response to the burn presents many of the same signs and symptoms as a developing infection (2) the burn damages many body systems, limiting the patient’s innate Ability to fight infection. [2]

Physiological Response to Burn Injuries

Burn injuries have local and systemic consequences. [2] This requires wound care professionals to work closely with interdisciplinary teams to properly monitor and manage patients in a holistic manner. Understanding the pathophysiological changes that occur after burn injury Injury will greatly enhance the wound care professional’s ability to prevent and/or control infection.

Local response to burn wounds

Local reactions involve the burned area and surrounding tissues. This is best described using Jackson’s burn model, which divides the wound into three regions. [3]

1. Jackson’s Burn Model

   Coagulation zone (also known as necrotic zone). This area suffers the most damage and suffers irreversible tissue loss.

2. stagnation zone. This area is located around the freezing zone. It indicates decreased tissue perfusion and thus can be salvaged with proper care. The area may also suffer complete tissue loss from prolonged hypotensive infection or edema.
3. Congested area. This is the outermost area of injury. Tissue perfusion is increased in this area. The area is likely to recover unless there is severe sepsis or chronic hypoperfusion.

For more information, check out this page.

Systemic response to burn wounds

Burns can cause damage to multiple body systems, which puts patients at a higher risk of infection. [2]

1. Cardiovascular function [4] and burn shock [3]
   • Increased capillary permeability leads to loss of intravascular protein and fluid into the interstitial compartment, resulting in edema [2][4]
   • Decreased myocardial contractility [4] Decreased cardiac output immediately following burn injury
   • When these changes are combined with fluid loss from the burn wound, they result in systemic hypotension and end-organ hypoperfusion [3]
   • Localized vascular damage occurs in deep localized and full-thickness injuries in which the arterial supply is compromised or destroyed by the burn [2]
2. Respiratory changes
   • Inflammatory mediators cause bronchoconstriction [4]
   • Acute respiratory distress syndrome (ARDS) can occur in severe burns [4]
   • Pulmonary function is affected by edema regardless of inhalation injury [3]
3. Metabolic changes[2]
   • Basal metabolic rate can be tripled after burning [4]
   • A systemic immunoendocrine response develops after extensive burns and can persist for up to 3 years. This response can lead to: (1) immunocompromised (2) sepsis (3) increased risk of bone fractures (4) reduced growth rate (5) decreased organ function (6) reduced wound healing and (7) death[3]
4. Gastrointestinal changes
   • Atrophy of the gastrointestinal mucosa, decreased intestinal blood flow, and impaired absorption [3]
   • Post-burn patients are in a state of persistent hypermetabolism due to the burn injury. Initially this will boost the energy response and help fight infection and start the healing process. However, as the hypermetabolic state becomes a prolonged response, it becomes an energy drain, and it It becomes more difficult for the patient to defend himself and continue the healing process. [2]
   • Early enteral feeding is essential to prevent malnutrition[3]
5. Immunological changes
   • Globally suppressed immune response after burn, severity depends on size of burn
   • Burns elicit both innate and adaptive immune responses [2]
   • Patients experience an exaggerated and prolonged inflammatory response [2]
   • Loss of the protective skin layer puts the body at risk of infection[3][2]
   • Immunocompromise further suppresses the body’s ability to fight infection – sepsis is the leading cause of death after burns [3]

Burn shock results from hypovolemia caused by direct tissue injury and the interaction of multiple inflammatory mediators that affect both microcirculation and cardiorespiratory function. [5]

Other Risk Factors for Burn Infection

Additional risk factors for burn infection: [2]

1. An increased length of stay in the ICU
2. Increased time waiting for test results (ie, wound culture or biopsy) to determine the source of infection delays the use of targeted antibiotics or antiseptics to most effectively treat the infection
3. Delays likely due to transport time to burn center for skilled active care
4. Delays in surgery due to patient medical instability or lack of surgical facilities
5. Any deep localized and/or full-thickness injury with a burn area greater than 20% of the body surface area is at high risk for infection regardless of the patient’s underlying condition
6. Infection risk increased more when patients were younger than 4 years or older than 55 years
7. Infection risk is increased in patients who are immunocompromised or have pre-existing comorbidities that put them at risk of infection
8. The presence of eschar in a wound increases the risk of infection

Signs and symptoms of burn wound sepsis

The detection of burn wound infection has multiple layers of complexity. A normal reaction to a burn resembles many of the signs and symptoms of an infection. Thus, the ability to recognize infection is overshadowed by the patient’s response to the burn. [2] Censorship Covert and Overt See this article for signs and symptoms of infection.

Although infection is one of the most common complications following burn injuries, sepsis is the leading cause of death in both adults and children with burn injuries. The diagnosis and management of burn sepsis also has multiple layers of complexity. Diagnosis in patients with sepsis Severe burns (>20% total body surface area) are complicated by clinical signs of a typical postburn hypermetabolic response overlapping with sepsis. [6]

To diagnose a burn wound as purulent, a patient must exhibit at least three of the following:

Table modified from: Norbury W et al. Al. Burn infection. Surgical Infection 2016; 17(2): 250-255. Not age specific AdultsChildrenTemperature>39°C or 102.2°F or 110 beats/min (bpm)> No pre-existing diabetes) untreated plasma glucose >200 mg/dL or equivalent mM/L insulin resistance. Examples include: >7 units of insulin/hour IV (in adults) Insulin resistance (>25% increase in insulin requirements over 24 hours) unable to continue Enteral feeding >24 hours Examples include: Bloating Enteral feeding intolerance (residual >150mL/h in children or 2 times feeding rate in adults) Uncontrolled diarrhea (>2500mL/d in adults or >400mL/d in children) Documented infection record one One of the following: culture-positive infection OR histologic source established OR clinical response to antimicrobials

Sources of Infection

Research has shown that burn wounds are sterile for the first 6-12 hours after the initial injury. Contamination occurs quickly, however, and bacterial growth rapidly increases. [2]

Contamination sources for burns: [2]

1. Normal skin flora
2. Endogenous sources such as the lungs or gut or any mucous membrane where the bacteria multiply in the normal system
3. Exogenous sources such as the environment or cross-contamination

Bacterial infections

For more in-depth information on bacterial infections, read this article.

Rough timeline of bacterial concentrations in burn wounds: [2]

• Early in infection: Gram-positive is usually the first to be detected
  • Staphylococcus aureus is often the first pathogen found in burn wound infections, including methicillin-resistant Staphylococcus aureus (MRSA)
  • Staphylococcus aureus is also often the first organism found in sepsis and wound arterial bacterial transmission
• Five days after injury: Gram-negative bacteria predominate,
  • Pseudomonas aeruginosa was the main bacterium identified. It is the most common pathogen in burn wounds and is very common in the formation of biofilms.
• Late stage: development of fungal or yeast infection independently of or in combination with pre-existing bacterial infection

Fungal infections

For more in-depth information on fungal infections, read this article.

Fungal infection is also a major concern for burn patients. It is often difficult to distinguish a fungal infection from a bacterial infection in a burn wound by appearance alone. [2]

Risk factors for fungal infection in burn wounds: [2]

1. Total body surface area involvement >30%
2. Long hospital length of stay
3. Multiple comorbidities

Clinical observation on fungal infection of burn wound: [2]

1. Changes in the wound appearance
   • Accidental separation of eschar is a key hallmark of fungal infection
2. Rapid transition from partial-thickness burns to deep partial-thickness or full-thickness burns
3. A blackening of the burn wound tissue
4. persistent fever that has not changed despite antibiotic treatment

Candida albicans and Aspergillus are the most common fungal pathogens. Aspergillus can be a very serious fungal infection requiring urgent evaluation and potential surgical debridement.

• Example of fungal wound infection. Image used with permission of Diane Merwarth PT.

Sample collection

Biopsy

Wound biopsy is an important diagnostic component in chronic wound management to monitor for potential malignancy or infection. [7] For a long time, tissue biopsy, especially of burn wounds, has been recognized as the gold standard. It is the most quantitative collection of tissue and To determine the extent of bacterial contamination or infection in the wound. [2]

Performing a wound biopsy involves sampling the wound edges and bed. The procedure is invasive and requires the skill of the nursing staff to collect the sample. Biopsy takes extra time to get results but allows for accurate targeting of antibiotics or antimicrobials For anti-infection. It has been found that bacteria are not homogeneously present in the wound bed, rather they accumulate in different areas. Therefore, multiple biopsies should be collected from a single burn wound. [2]

A wound biopsy is also recommended for wounds that do not respond to treatment after 2-6 weeks. [7]

Semiquantitative swab culture

Controversy exists regarding the validity of performing swab cultures and whether the results represent infection. However, studies have shown a correlation between bacteria identified in swab cultures and bacteria identified from tissue samples, especially biopsies. cotton swab Culture will not provide the same level of quantitative results as biopsy, but if performed properly, the results will identify microorganisms that require antimicrobial intervention. [2]

Benefits of performing a swab culture:[2]

• Less invasive than a biopsy
• Easily performed by bedside clinicians
• Provides faster results, allowing for more timely targeted antimicrobial interventions

General guidelines for treating burn wound infections

Unfortunately, there is no standardized protocol for treating burn wound infections. [2]

Topical antimicrobial agents[2]

• These treatments need to be individualized
• Initiate topical antiseptics once local infection is identified
• Initiate systemic antimicrobials for dissemination or systemic infection
• More than one broad-spectrum antibiotic may be used while awaiting tissue sample results
• Fungal infection requiring topical and antifungal agents and possibly surgical debridement
• Due to the rapidly forming nature of biofilms, treatment may include biofilm-based wound management

.

• Biofilm populations will need to be removed. Wounds often require frequent surgical debridement. It has been found that biofilms will begin to reorganize within 24 hours of being disrupted and mature within three days. Therefore, it is important to take appropriate follow-up Biofilm-based wound management.
• Fungal infection may require surgical debridement
• Early removal of eschar provides a good environment for bacterial proliferation
• Skin grafts instantly close wounds and reduce exposure to new sources of infection

Infection Prevention[2]

1. Vigilance
   • Watch closely for overt and subtle signs and symptoms of infection
   • Closely monitor vital signs and laboratory values for signs of infection
   • Accurate and thorough documentation of wound appearance and characteristics
2. Frequently reevaluate and update care plans based on patient response to current interventions
3. Manage patient’s comorbidies
4. Maintain optional nutrient and water intake
   • Oral is the most valuable and effective method
   • Nasogastric tube is the second most effective method
   • Enteral nutrition is the least popular as it does not utilize the gut
5. Manage oedema
   • Elevate limbs to reduce edema
   • Apply compression bandages to extremities if tolerated
6. Provide psychosocial support and education
   • A Positive Mindset Helps Wound Heal and Prevent Infection
   • Include the patient in care plans
7. Temperature control
   • Regulates the temperature of a patient room or operating room (OR) by preventing the patient from getting too hot or too cold. Hospitals typically set room temperature to a minimum of 29-31°C (85-88°F) to prevent burn patients from becoming too cold.
   • Dressing Considerations: Wounds cool down when they become saturated with drainage fluid or are exposed to air for too long during dressing changes.
8. Recommended Strategies for Minimizing Infection Episodes in Healthcare Facilities
   • Universal precautions Proper use of personal protective equipment (PPE) and hand hygiene
   • Patients at high risk of infection should be placed in negative pressure wards and strict isolation measures should be taken.
   • Wound care should use aseptic (sterile) techniques whenever possible, and clean (non-sterile) techniques should be used otherwise.
   • Strict aseptic technique should be used when inserting any type of device (intravenous intraarterial foley catheter). It is also recommended that these devices be removed once they are no longer needed to support the patient’s recovery from burns.
   • Environmental controls include: (1) Thorough cleaning of the patient room twice daily wiping down all high-touch surfaces (2) Final cleaning of the room when the patient is not present (3) Three days are recommended for the room after the patient is discharged The terminal was cleaned before being used by another person.
9. Many burn centers recommend monitoring cultures
   • This includes nasal cultures wound cultures possibly anal cultures vancomycin resistant enterococci (VRE)
   • Weekly culture collections are recommended on admission and throughout the hospital stay

Resources

Optional Additional Recommended Reading:

• Hettiaratchy S Dziewulski P. Pathophysiology and burn types. Bmj. 2004 Jun 10;328(7453):1427-9.
• Nunez Lopez O et al. Al. Prediction and management of sepsis in burn patients: current perspective. therapy. clinical. Risk Management 2017;17: 1107-1117

Optional Video:

Watch this optional video for an overview of burn wound anatomy and classification and a detailed description of burn wound pathophysiology.

[8]