World J. Surg. 16, 10-15, 1992
World Journal of Surgery O 1992 by the So¢!6t~ lnternational¢ de Chirurgie
Burn Depth: A Review David Heimbach, M.D., L o r e n Engrav, M.D., Baiba Grube, M.D., and Janet Marvin, R . N . , M.N. The University of Washington Burn Center, Harboview Medical Center, Seattle, Washington, U.S.A. Despite the plethora of technologic advances, the most common technique for diagnosing burn depth remains the clinical assessment of an experienced burn surgeon. It is clear that this assessment is accurate for very deep and very shallow burns. But since clinical judgment is not precise in telling whether a dermal burn will heal in 3 weeks, efforts to develop a burn depth indicator are certainly warranted to accurately determine which dermal burns to excise and graft. This review summarizes the considerable literature in which a variety of techniques to determine burn depth have been used.
Along with extent of burn and the age of the patient, the depth of burn is a primary determinant of mortality following thermal injury. Burn depth is also the primary determinant of the patient's long term appearance and function. For many years burns were treated by daily washing, removal of loose dead tissue, and some sort of topical nostrum until they healed by themselves or eventually granulation tissue appeared in the base of the wound. Superficial dermal burns healed within 2 weeks and deep dermal ones healed over many weeks if infection was prevented. Full thickness burns lost their eschar in 2 to 6 weeks by collagenase production from bacteria and mechanically by the daily debridement. When the granulating bed became free of debris and relatively uninfected, split-thickness skin grafts were then applied, usually some 3 to 8 weeks after injury, and a50% grafttake was considered to be acceptable. Repeated graftings eventually closed the wound. The Prolonged and intense inflammatory response made hypertrophic scar and contractures part of normal burn treatment. Vigorous physical therapy, nutritional support, psycho-social support, and pain management were required on a daily basis for many Weeks to yield a satisfactory result. Such is no longer the case. Rather than waiting for spontaneous separation, the eschar is now surgically removed and the wound closed with grafting techniques and acute flaps individualized to each patient. Several technical advances have made this possible. We have "safer" blood, better monitoring equipment and methods, and a better understanding of the altered physiology and the increased metabolic demands of patients with major burns. The ability to stabilize the patient within a few days of the injury has enabled the surgeon to remove deep Reprint requests: David Heimbach, M.D., Harboview Medical Center ZA-16, 325 Ninth Ave, Seattle, Washington 98104, U.S.A.
burn wounds before they become invasively infected. A number of advantages have become clear with an aggressive surgical approach to both large and small burns, Early wound closure shortens hospital stay and duration of illness [1] for adults [2], the elderly [3], and children [4, 5]; and for large burns [6], moderate burns [7], and small burns [8]. Although early studies did not demonstrate dramatic differences in cosmetic and functional results [9], as surgeons have become more experienced, both improved function and appearance are being demonstrated. This is particularly true with burns of the face [10, 11], hands [t2-I6], and feet [17]. When nonoperative treatment is the routine, the accurate assessment of burn depth is of little importance except for predicting mortality. On the other hand, with aggressive surgical treatment, an accurate estimation of burn depth becomes crucial. Burns that heal within 3 weeks generally do so without hypertrophic scarring or functional impairment, although long term pigmentary changes are common. Burns that take longer than 3 weeks to heal often produce unsightly, hypertrophic scars and frequently lead to functional impairment, as well as providing only a thin, fragile epithelial cover for many weeks or months. State of the art care now, at least in patients with small and moderate burns, involves early excision and grafting of all burns that wilt not heal within 3 weeks [18, 19]. The challenge is to determine which burns will heal within 3 weeks. An understanding of burn depth requires an understanding of skin thickness. The living epidermis is an intensely active layer of epithelial cells under layers of dead keratinized cells and is superficial to the active structural framework of the skin, the dermis. The thickness of skin varies both with the age and sex of the individual and with the part of the body considered. The thickness of the living epidermis is relatively constant, but keratinized (dead and cornified) epidermal cells may reach a height of 0.5 cm on palms of hands and soles of feet. The thickness of the dermis, on the other hand, may vary from 5 mm on the posterior trunk. Although the proportional thickness of skin in each body area is similar in children, infant skin in each specific area may be less than half that of adult skin; the skin does not reach adult thickness until approximately 5 years of age. Similarly, in patients over 50 years of age dermal atrophy begins such that all areas of skiri become quite thin in elderly patients. The depth of burn is dependent on the heat of the burn source, the thickness
D. Heimbach et ai.: Burn Depth
of the skin, the duration of contact, and the heat dissipating capability of the skin (blood flow). Thus, an identical scald in an infant or elderly patient will be deeper than in a youngadult [20]. A diabetic with impaired sensation or an inebriated patient with an impaired sensorium who lies on a heating pad all night may sustain a full-thickness burn because of the long duration of contact with the pad and pressure of the body weight which occludes cutaneous blood flow and prevents heat dissipation. The standard technique for determining burn depth has long been clinical observation of the wound. Unfortunately, the burn depth difference between a burn that heals in 3 weeks, a deep dermal burn that will heal only after many weeks, or a fullthickness burn that won't heal at all may be only a matter of a few tenths of a millimeter. Further, a burn is a dynamic process for the first few days and a burn that appears shallow on day 1 may appear deep by day 3. Finally, the kind of topical wound care used can dramatically change the appearance of the burn. Because of these limitations, and because of its increased importance in planning definitive burn wound care, interest has been stirred and technology has been developed for numerous devices and techniques to determine burn depth more precisely than clinical observation. Clinical Observation
Despite modern technology, clinical observation still remains the standard for diagnosis. Very shallow (heal in
World Journal of Surgery O 1992 by the So¢!6t~ lnternational¢ de Chirurgie
Burn Depth: A Review David Heimbach, M.D., L o r e n Engrav, M.D., Baiba Grube, M.D., and Janet Marvin, R . N . , M.N. The University of Washington Burn Center, Harboview Medical Center, Seattle, Washington, U.S.A. Despite the plethora of technologic advances, the most common technique for diagnosing burn depth remains the clinical assessment of an experienced burn surgeon. It is clear that this assessment is accurate for very deep and very shallow burns. But since clinical judgment is not precise in telling whether a dermal burn will heal in 3 weeks, efforts to develop a burn depth indicator are certainly warranted to accurately determine which dermal burns to excise and graft. This review summarizes the considerable literature in which a variety of techniques to determine burn depth have been used.
Along with extent of burn and the age of the patient, the depth of burn is a primary determinant of mortality following thermal injury. Burn depth is also the primary determinant of the patient's long term appearance and function. For many years burns were treated by daily washing, removal of loose dead tissue, and some sort of topical nostrum until they healed by themselves or eventually granulation tissue appeared in the base of the wound. Superficial dermal burns healed within 2 weeks and deep dermal ones healed over many weeks if infection was prevented. Full thickness burns lost their eschar in 2 to 6 weeks by collagenase production from bacteria and mechanically by the daily debridement. When the granulating bed became free of debris and relatively uninfected, split-thickness skin grafts were then applied, usually some 3 to 8 weeks after injury, and a50% grafttake was considered to be acceptable. Repeated graftings eventually closed the wound. The Prolonged and intense inflammatory response made hypertrophic scar and contractures part of normal burn treatment. Vigorous physical therapy, nutritional support, psycho-social support, and pain management were required on a daily basis for many Weeks to yield a satisfactory result. Such is no longer the case. Rather than waiting for spontaneous separation, the eschar is now surgically removed and the wound closed with grafting techniques and acute flaps individualized to each patient. Several technical advances have made this possible. We have "safer" blood, better monitoring equipment and methods, and a better understanding of the altered physiology and the increased metabolic demands of patients with major burns. The ability to stabilize the patient within a few days of the injury has enabled the surgeon to remove deep Reprint requests: David Heimbach, M.D., Harboview Medical Center ZA-16, 325 Ninth Ave, Seattle, Washington 98104, U.S.A.
burn wounds before they become invasively infected. A number of advantages have become clear with an aggressive surgical approach to both large and small burns, Early wound closure shortens hospital stay and duration of illness [1] for adults [2], the elderly [3], and children [4, 5]; and for large burns [6], moderate burns [7], and small burns [8]. Although early studies did not demonstrate dramatic differences in cosmetic and functional results [9], as surgeons have become more experienced, both improved function and appearance are being demonstrated. This is particularly true with burns of the face [10, 11], hands [t2-I6], and feet [17]. When nonoperative treatment is the routine, the accurate assessment of burn depth is of little importance except for predicting mortality. On the other hand, with aggressive surgical treatment, an accurate estimation of burn depth becomes crucial. Burns that heal within 3 weeks generally do so without hypertrophic scarring or functional impairment, although long term pigmentary changes are common. Burns that take longer than 3 weeks to heal often produce unsightly, hypertrophic scars and frequently lead to functional impairment, as well as providing only a thin, fragile epithelial cover for many weeks or months. State of the art care now, at least in patients with small and moderate burns, involves early excision and grafting of all burns that wilt not heal within 3 weeks [18, 19]. The challenge is to determine which burns will heal within 3 weeks. An understanding of burn depth requires an understanding of skin thickness. The living epidermis is an intensely active layer of epithelial cells under layers of dead keratinized cells and is superficial to the active structural framework of the skin, the dermis. The thickness of skin varies both with the age and sex of the individual and with the part of the body considered. The thickness of the living epidermis is relatively constant, but keratinized (dead and cornified) epidermal cells may reach a height of 0.5 cm on palms of hands and soles of feet. The thickness of the dermis, on the other hand, may vary from 5 mm on the posterior trunk. Although the proportional thickness of skin in each body area is similar in children, infant skin in each specific area may be less than half that of adult skin; the skin does not reach adult thickness until approximately 5 years of age. Similarly, in patients over 50 years of age dermal atrophy begins such that all areas of skiri become quite thin in elderly patients. The depth of burn is dependent on the heat of the burn source, the thickness
D. Heimbach et ai.: Burn Depth
of the skin, the duration of contact, and the heat dissipating capability of the skin (blood flow). Thus, an identical scald in an infant or elderly patient will be deeper than in a youngadult [20]. A diabetic with impaired sensation or an inebriated patient with an impaired sensorium who lies on a heating pad all night may sustain a full-thickness burn because of the long duration of contact with the pad and pressure of the body weight which occludes cutaneous blood flow and prevents heat dissipation. The standard technique for determining burn depth has long been clinical observation of the wound. Unfortunately, the burn depth difference between a burn that heals in 3 weeks, a deep dermal burn that will heal only after many weeks, or a fullthickness burn that won't heal at all may be only a matter of a few tenths of a millimeter. Further, a burn is a dynamic process for the first few days and a burn that appears shallow on day 1 may appear deep by day 3. Finally, the kind of topical wound care used can dramatically change the appearance of the burn. Because of these limitations, and because of its increased importance in planning definitive burn wound care, interest has been stirred and technology has been developed for numerous devices and techniques to determine burn depth more precisely than clinical observation. Clinical Observation
Despite modern technology, clinical observation still remains the standard for diagnosis. Very shallow (heal in
