Hyperbaric Treatment of Thermal Burns

Excerpt

Thermal burns are common in the United States, and approximately 2 million people are injured every year, with about 155 per million patients needing admission to a hospital and 6500 cases resulting in death (see Image. Thermal Burn). Burns are complex and dynamic injuries that cause profound activation of platelets and white cells, destruction of the microvasculature by coagulation or thrombosis, and accumulation of edema. Medical treatment of burns is critical, especially when they are second-degree or worse and when a substantial amount of body surface area is affected. There are multiple factors as to why thermal burns are difficult to treat, and hyperbaric oxygen therapy (HBO) can be used as part of the treatment regimen to reduce healing time and improve outcomes.

The characteristic of a burn is described as a zone of coagulation, surrounded by an area of stasis and bordered by erythema. The destruction and obstruction of microvascularization impede cellular and humoral immunity and alter macrophage function. The microcirculation is compromised to the greatest extent during the first 12 to 24 hours after the burn. The injury can remain in a state of flux for 72 hours, and the lack of oxygenation causes ischemic necrosis rather quickly. The burn also causes extensive edema, which is caused by an increase in capillary permeability, leading to hypoproteinemia. This causes a decrease in intravascular oncotic pressure, and fluid can easily leak out of the vasculature and into the interstitial space.

The goals of treating burns are minimizing the edema, keeping tissue viable in the stasis zone of the burn, protecting the microvasculature, and enhancing host defenses to stave off infection. HBO addresses these physiological derangements and can be beneficial to patients. Once the patient is stabilized, treatment is aimed at patient survival, rapid wound healing, and reduced scarring/abnormal pigmentation, all while being cost-effective. Early treatment of thermal burns is critical. It is important to initiate fluid resuscitation as quickly as possible, and the patient sometimes requires several liters acutely. The treatment team should aim to decrease fluid losses from the wound and slow bacterial growth. Topical agents and antibiotics are used for infection and are often used for prophylaxis in certain circumstances. Debridement and placement of a skin graft or flap help control bacterial growth and fluid loss.

The most concerning element of a thermal burn is an infection, the leading cause of death from burns. This is due to a loss in the integumentary barrier that leads to bacterial invasion and growth and obstructed or compromised microvasculature that prevents cellular and humoral elements from reaching the burn site. The immune system is dampened, limiting immunoglobulins and macrophage function in chemotaxis, phagocytosis, and other antibiotic properties. Besides infection, burns can lead to a myriad of different comorbidities as well, which include pneumonia, respiratory failure, cellulitis, urinary tract infection, and sepsis.

Since 1965, HBO therapy has been suggested to improve outcomes in thermal burns after it was observed to heal second-degree burns faster in a group of coal miners being treated for carbon monoxide therapy. The skin adjacent to second and third-degree burns is more hypoxic than normal skin, and continued studies have shown that hypoxic tissue surrounding the burn site can be returned to normal oxygen levels with oxygen administration under pressure. It has been shown to decrease edema through vasoconstriction, preserve microcirculation, and enhance oxygen delivery by a direct osmotic effect. HBO also aids in the deactivation of white cell adhesion.

Most studies of hyperbaric treatment of burns have been reported using various animal burn models, showing that HBO therapy is beneficial in reducing edema, decreasing fluid requirements, preserving dermal structures with improved vascularity, and increasing immune response. In human studies, the results have varied but support the potential benefit of HBO therapy as an adjunct therapy. A Cochrane review was published in 2004 that looked at 2 small randomized trials. These studies demonstrated improved healing, decreased mortality, reduced hospital stay, and decreased need for surgery. However, some studies have shown little to no benefit with HBO therapy. Insufficient evidence is available to support the routine use of patients with thermal burns, although it is a widely used adjunct therapy. Hyperbaric oxygen does have the potential to decrease healing time and fluid requirements, as well as increase the success of skin grafts, but more studies must be conducted to adopt this into routine practice as this therapy requires complex equipment, procedures, and specialized skills in a constricted environment, which may become unsafe when caring for critically ill burn patients.