The prognosis for patients with burn injuries is determined by the size, depth, location, and type of burn as well as related factors such as age, pre-existing conditions, and associated injuries (Djmjcki.,1994.).
The size of a burn injury is usually expressed in terms of the percentage of the body surface area involved. This measurement is utilized to predict resuscitation fluid volumes and to assess prognosis. Unfortunately, this number is not readily apparent on inspection of the patient. The simplest and most widely used guide for estimating burn wound size is the rule of nines (Fig 1), which equates each major body part (e.g. a limb) to 9 per cent, or a multiple of 9 per cent, of the body surface area. This handy rule of thumb is sufficiently reliable for most purposes in adult burn patients, but introduces significant error for young children owing to their disproportionately larger heads. If burn size is being estimated in very young children or if precise estimates are necessary, the age-corrected diagrams shown in Fig. 2 are more appropriate. It is often difficult to apply either of these systems to small scattered burns, and the rule of palms may be helpful in such cases. The patient's palmar surface (not the examiner's) is approximately equal to 1 per cent of the body surface area.
Fig. 1 The rule of nines. This is a simple rule of thumb for the estimation of burn size. Each major body part is either 9 per cent or a multiple of 9 per cent of the body surface area. This rule works well enough for routine purposes in adults but is much less reliable for young children owing to the disproportionately larger head.
Fig. 2 The Lund-Browder chart. This chart allows more precise estimation of the body surface area injured. The area of burn is drawn on the figure and then estimated either visually or by planimetry. This chart also allows easy age-specific correction.
Burn wound depth is measured not in millimeters but in terms of which epidermal structures are destroyed. Thus a burn of depth 2 mm on the dorsum of an elderly hand is much 'deeper' than a burn of depth 2 mm on an adolescent's back. Traditionally, burn depth has been classified as first, second, or third degree. First-degree burns, similar to a sunburn, involve only the epidermis and are characterized by erythema and mild discomfort. Such injuries heal in a few days and produce essentially no systemic effects. The area involved in such epidermal burns should not be included in estimates of burn size since they do not contribute to fluid requirements or outcome determinations. Second-degree burns, more descriptively known as partial-thickness burns, represent destruction through the epidermis and to varying depths in the dermis. Such burns have the capacity to regenerate an epidermal layer from the epidermal cells lining skin appendages such as hair follicles and sweat glands which are embedded in the dermis. Many of these burns will heal within 2 to 3 weeks with an acceptable functional and cosmetic result. As the coagulation necrosis extends deeper into the dermis, fewer appendages remain and a longer period of time is required for re-epithelization of the wound. Healing in this fashion is often associated with excessive scarring and contractures which compromise mobility. Third-degree or full-thickness burns have no surviving epidermis or dermis. Such wounds can heal only by epithelial ingrowth from the margins and contracture. If these injuries are more than a few centimeters in size, they require skin grafting to heal.
Since many burn clinicians believe that patients with full-thickness and even deep partial-thickness burns benefit from early aggressive excision and skin grafting, it is crucial to be able to distinguish burn depth early in the patient's course. Superficial partial-thickness injuries characteristically form watery blisters, although these may not appear for several hours after the injury. When the blister is removed, the underlying tissue is moist, pink, and hypersensitive to touch. Because of the increased dermal blood flow, these wounds blanch when pressure is applied. In contrast, full-thickness wounds are firm, dry, and leathery. They have diminished sensitivity to light touch or needle prick, and may show coagulated dermal vessels. Classifying either of these wound types is relatively simple. Unfortunately, many patients have burns which do not fall clearly into either category. Such wounds may blister, but the underlying surface is mottled and does not blanch with pressure. Some sensation is preserved, but they are less sensitive than surrounding skin. Even experienced burn clinicians do not achieve an accuracy of better than 50 to 60 per cent in evaluating such wounds. In addition to physical examination, the mechanism of injury often provides valuable clues to burn depth. For example, scald burns without prolonged contact, such as a splash of hot liquid, often produce superficial partial-thickness wounds, while burning clothing almost always produces either deep dermal or full-thickness injury.
The area of the body involved in burn injury has little effect on resuscitation requirements or survival, but has a major impact on functional and cosmetic outcome. Traditional high-risk areas include the face, hands, feet, and perineum. Facial burns from flame should suggest the possibility of smoke inhalation. The eyes should be examined both directly and with the use of fluorescein and ultraviolet light to detect corneal or conjunctival injury. If burns involve the periorbital area, the patient should be warned to anticipate swelling which may prohibit opening the eyes and often lasts for 48 h. Advance warning will often avoid needless anxiety. Hand burns impair the patient's ability to feed and care for him- or herself. This impairment may last for only a few days as the result of pain and swelling; however, if the burn is deeper multiple surgical procedures and months of therapy may be required to produce acceptable function. Burns of the feet impair the patient's mobility and may lead to toe contractures and long-term problems with gait. Perineal burns present problems in controlling fecal contamination and the potential for scarring and contracture compromising genitourinary function.
Age is probably the most important of the non-burn-specific factors in determining outcome. Patients at either extreme of age have significantly poorer prognosis than children and young adults. There is still significant debate regarding the optimal approach to burn care in the elderly. Should they be treated with early aggressive excision or with a slower and more conservative strategy? Neither approach produces a significant chance of survival of the elderly with burns larger than 35 to 40 per cent (A.npus..and Heimbach 1986). Associated injuries such as fractures may complicate both the management of the burn wound and the patient's rehabilitation. The stress of a major burn injury may aggravate pre-existing medical conditions, leading to delays in necessary surgery or increases in morbidity and mortality.
Numerous authors have combined these factors to produce mathematical models of burn patient survival. Like all statistical methods they must be applied cautiously to the individual patient, but they do provide some generalizations regarding outcome.
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