Burn Wound Infections: Treatment and Care

Introduction:

Any rapid and noticeable changes in the clinical condition or the appearance of the burn wound may lead to burn wound infection or sepsis (the body’s life-threatening response to an infection). Successful management and burn wound closure at the appropriate time are essential to ensure the patient's survival. Before the advent of effective topical antimicrobial prophylaxis in 1964, death from invasive burn wound infection occurred in 60 % of the patients at the U.S. Army Institute of Surgical Research (the U.S. Army Burn Center).

How Are Burn Wound Infections Caused?

The extent to which a burn patient is prone to infection is proportional to the degree of burn caused. Burn infections are caused due to the following reasons:

• The skin acts as a barrier to the entry of microorganisms, and loss of this barrier in burn patients paves the way for the entry of microorganisms to invade the underlying tissues over a broad area and the protein-laden, avascular eschar (dead tissues that are shed from healthy skin) acts as an excellent culture medium to facilitate this.

• Burn injury also interferes with the normal functioning of the immune system, like impaired neutrophil function, decreased lymphocyte count, decreased production of IgG and IL-2, and reversal of the T-helper to T-suppressor cell ratio.

• The density of microorganisms, antimicrobial resistance, and other factors also influence burn wound infections. Any microorganism can cause burn wound infection in severely immunocompromised persons. The major microorganism which causes burn wound infection is Pseudomonas aeruginosa.

What Are the Types of Burn Wound Infections?

The following are the types of burn wound infections:

• Burn Wound Impetigo: Impetigo results from the loss of epithelium from a surface that has been re-epithelialized previously, such as partial-thickness burns which were allowed to close by secondary intention, grafted burns or healed donor sites. Burn wound impetigo is not linked with mechanical disruption of the graft, inadequate excision of the burn, or hematoma (blood clot in an organ, tissue, or body space) formation.

• Burn-Related Surgical Wound Infection: These infections involve both donor sites and excised burn wound areas that have not yet been epithelialized (the process of covering exposed epithelial surface). The exudate from the wound is culture positive. Surgical wound infections, especially in the open areas, are characterized by changes in the appearance of the wound, loss of biological or synthetic covering of the wound, and erythema (superficial reddening of the skin) in the skin surrounding the wound that is not injured.

• Burn Wound Cellulitis: Burn wound cellulitis arises when the infection invades the healthy, uninjured skin and the soft tissues surrounding the burn wound or the donor site. This can be appreciated by the appearance of erythema that extends into the uninjured skin surrounding the burn. Though burn wound cellulitis is not related to other signs of wound infection, at least one of the following may be present, namely, heat or swelling at the affected site, localized pain or tenderness, progression of erythema and swelling, and signs of lymphadenitis (infection in one or more lymph nodes) or lymphangitis (infection of the lymph vessels) that extend from the affected site along the paths of lymphatic drainage to that area.

• Invasive Infection in Unexcised Burn Wounds: Patients with unexcised wounds that include both partial-thickness and full-thickness burn wounds are more susceptible to developing an invasive infection. Successful treatment involves surgical excision of the wound accompanied by other medical measures.

How to Identify Early Infection in a Burn Wound?

One of the early cues to identify the onset of infection in a burn wound is the change in the appearance of the wound. Cellulitis appears commonly in many surface infections. Cellulitis is an infection caused by bacteria which is characterized by red, warm, swollen, or tender skin around the wound site. Sometimes even a red streak or a red line can originate from the wound. At the initial stage of infection, the burn wound appears red around the outer edges. This redness may begin to invade the surrounding areas with time. In addition, the wound may be warm, tender, and painful. If the infection aggravates, a foul odor may arise from the burn wound accompanied by fever.

What Are the Risk Factors for Burn Wound Infection?

The risk factors include:

• Prolonged stay in the ICU (intensive care unit).

• Increased waiting period for test results like wound cultures or biopsies. The tests are taken to detect the source of infection, which delays the administration of antimicrobial agents or targeted antibiotics used to treat the infection.

• A delay in taking the burn victim to a burn center for skilled and timely care.

• Sometimes, a lack of proper surgical facilities or the patient’s medical instability can delay the surgery, resulting in infection.

• Any kind of burn which is greater than 20 % of the total body surface area of deep partial/full thickness burn injury is highly prone to infection irrespective of the patient’s underlying conditions.

• Age also poses a risk to burn wound infection. The risk of infection is higher in kids under four years of age or adults over 55 years of age.

• Those who are immunocompromised or with accompanying comorbidities can increase the risk of infection.

• The presence of eschar (dead tissues that are shed from healthy skin) in the burn wound also poses a threat of developing a burn wound infection.

What Are the Signs and Symptoms of Burn Wound Infection?

The body’s improper response to an infection is called sepsis, and sepsis is one of the major causes of death in pediatric and adult burn patients. The signs and symptoms of various burn wound infections are as follows:

• Sepsis: The signs and symptoms of sepsis include:

1. Rise in temperature.

2. Progressive tachycardia (an abnormally rapid heart rate).

3. Progressive tachypnea (abnormal, rapid breathing).

4. Thrombocytopenia (low blood platelet count-this condition is not applicable until 3 days after initial resuscitation).

5. Hyperglycemia (elevated blood glucose level) in the absence of already existing diabetes mellitus.

6. Inability to proceed with enteral feedings (supply of nutrients directly into the gastrointestinal tract) for more than 24 hours.

7. Presence of infection that has been confirmed through a culture test or identified from a pathologic tissue source.

• Bacterial Infections: In the early stage of infection, Staphylococcus aureus is the first microorganism to be identified in burn wound infection, including the Methicillin-resistant Staphylococcus aureus (MRSA). After five days following burn injury, Pseudomonas aeruginosa is common in burn wounds and contributes to the development of biofilms. In the later stages, fungal or yeast infections can either occur independently or in unison with a pre-existing bacterial infection.

• Fungal Infections: The signs and symptoms of fungal infections include:

1. There will be a change in the wound appearance, especially the unanticipated separation of eschar, which is the classical sign of invasion of fungal infections in a burn wound.

2. A partial-thickness burn gets rapidly converted to a deep-thickness or a full-thickness burn wound.

3. The burn wound tissues start to blacken.

4. A persistent fever that remains unaffected by antibiotic therapy.

How Are Samples Collected for Diagnosing Burn Wound Infection?

The samples are collected in the following ways:

• Biopsy: Examining the tissue biopsy of burn wounds has been considered the gold standard for detecting the level of bacterial manifestation in the wound. The sample is usually obtained from the wound edge and the wound bed. This procedure requires expertise since the procedure is invasive. Though the biopsy results are obtained after a long time, the results are precise and enable the healthcare provider to provide targeted antibiotics or antimicrobials to treat the infection. Since the bacteria are not spread uniformly in the wound, multiple biopsies should be obtained from a single burn wound. Biopsies are also recommended in cases where the wounds remain unresponsive to treatment even after 2 to 6 weeks.

• Semiquantitative Swab Culture: A controversy prevails over this diagnostic method since there is doubt whether this method will identify the infection correctly. Research has studied the correlation between the bacteria identified from a tissue sample like a biopsy and those identified through a swab culture. Unlike biopsies, a swab culture may not offer the level of quantitative results. Still, if done correctly, the results will detect the microorganisms that need to be aimed at with antimicrobial interventions. Furthermore, the advantages of performing a swab culture are:

1. Less invasive when compared with a biopsy.

2. It can be performed easily at the bedside.

3. Offers quick results which allow the timely intervention of targeted antimicrobial therapy.

How Are Burn Wound Infections Treated?

Burn wound infections are treated in the following ways:

• The treatment should be customized for each patient based on the infection status. In case of identification of local infection, topical antimicrobial agents like 2.5 % Mafenide solution should be started. If no improvement is noticed with topical antimicrobial agents, systemic antibiotics should be initiated.

• Treatment with more than one broad-spectrum antibiotic may be started while waiting for tissue sample results.

• Fungal infections may need a combination of antifungal and topical therapy with the potential for surgical debridement.

• Since biofilms also develop rapidly, the treatment also involves biofilm-based wound management.

• Surgical intervention may be required to eliminate the biofilm population. The wound may also require frequent surgical debridement. The biofilms tend to reappear within 24 hours of destruction and can mature in three days. So, proper follow-up with suitable biofilm-based wound management is necessary.

• Surgical debridement may be required in case of fungal infections.

• Excision of eschar (dead tissues that are shed from healthy skin) in the early stages is recommended since eschar offers a viable environment for the proliferation of bacteria.

• Skin grafts should be used to close the wound as early as possible to prevent exposure to new sources of infection.

How to Prevent Burn Wound Infections?

Different ways to prevent burn wound infections are as follows:

• The burn wound must be closely observed and monitored for any changes in appearance, presence of any signs and symptoms of infection, and watchful observation of vital signs and lab values to detect the presence of infection.

• Based on how the patient responds to the current medical interventions, medical care should be reassessed and updated frequently.

• The patient’s comorbidities should be managed appropriately.

• Optimal nutritional and water intake should be ensured. The first effective method to ensure this is an oral intake, followed by nasogastric intake and enteral nutrition. Enteral nutrition is the least effective since it does not utilize the gut.

• Edema should be managed by elevating the extremities or applying compression bandages to the extremities if tolerated.

• Helping the patient maintain a positive mental attitude can help with the process of wound healing and the prevention of infection.

• The patient should be kept in an environment that is neither too hot nor too cold. Usually, hospitals maintain an optimal temperature of 29-31 degree Celsius (85-88 degree Fahrenheit) that suits the burn patients. Care should be taken in wound dressings as wounds can cool down when the dressings become wet with drainage or when exposed to air for a long time while changing a dressing.

• Proper hand hygiene and use of personal protective equipment (PPE) should be maintained.

• Those who are highly prone to developing an infection should be kept under strict isolation in a negative pressure room.

• A strict aseptic technique should be followed while inserting any device, like a Foley catheter, intravenous line, or intra-arterial line. These devices should be removed as early as possible if not required.

• The patient’s room should be maintained clean. Cleaning should be done at least twice a day. The room should also be cleaned continuously for three days, even after the patient gets discharged, before another person uses it.

• Cultures should be collected frequently, and it is suggested that cultures be collected immediately after admission and weekly throughout the patient’s stay at the hospital.

Conclusion:

With the discovery of effective antimicrobial creams, the management of burn patients has improved with a remarkable decrease in mortality. Other successful interventions include burn wound excision and grafting, prevention of stress ulcers, infection control practices, improvements in mechanical ventilation, and the development of enteral nutrition techniques. Close vigilance and regular examination of burn wounds for any signs of infection are mandatory to prevent the development of burn wound infections.