Tangential debridement has been traditionally performed with a dermatome [Humby (Down, Sheffield, U.K.) or Watson (Integra, Plainsboro, N.J.) knife] (Fig. 1) or a guarded knife (Goulian/ Weck knife) (Fig. 2). These instruments can remove very thin slices of tissue (down to 0.006 in) at each passage.
Determining the Level of Excision
One of the challenges with tangential excision is how far down to debride. Debriding too far will result in the loss of valuable dermis, and conversely inadequate debridement will lead to graft loss. For small areas on limbs, or for areas on the head, neck, or trunk for which a tourniquet cannot be used, an acceptable wound bed is identified by active punctate bleed- ing (Fig. 3). The problem however arises where a tourniquet has been placed on an exsan- guinated limb to minimize bleeding. In this situation, great experience is needed to recognize healthy tissue by its color and texture from devitalized tissue. Some surgeons choose to facili- tate this process by not having the limb exsanguinated prior to inflation of the cuff. In this situ- ation bleeding can still be observed, although at a much reduced level (15). Another technique used is to apply the dye methylene blue topically to the burn surface. The assumption is that the dye will only stain dead tissues which can be removed leaving the healthy unstained tissue behind (16). Alternatively, some surgeons have used intravenous fluorescein with the assump- tion that only living tissues will take up the stain. It is of special value in hand burns (17).
The percentage of body surface area which can undergo tangential debridement at one sit- ting depends on several factors. These factors include the stability of the patient, the adequacy of the anesthesia and the surgical team performing the procedure, and the utilization of tourni- quets. For large burns several surgical teams can work simultaneously on different body areas.
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FIGURE 1
This strategy will not only speed up the procedure, but allow larger areas to be debrided with less cooling owing to prolonged patient exposure. For large burns central venous access, an arte- rial line, a nasogastric tube, and a urinary catheter are usually required. Under optimal condi- tions, up to 20–40% total body surface area can be debrided at one sitting.
Control of Blood Loss
Blood loss during debridement is inevitable but should be kept to a minimum. Blood loss can vary greatly (18); however, anticipated blood losses are 0.75 ml/cm2of area of excision during 2–16 days postburn, or 0.40 ml/cm2if excision is performed during the first 24 hours (19). Strate- gies to minimize blood loss include: tourniquets, local pressure, topical thrombin, and subcuta- neous adrenaline (epinephrine) and para-ornithin-8-vasopressin (POR-8). As stated before, the use of tourniquets on limbs can drastically reduce blood loss. Their use, followed by the appli- cation of firm supportive dressings, have been shown to reduce blood loss by as much as 80% (20). Subcutaneous infiltration of adrenaline has been used successfully to reduce blood loss (18). However, side effects of excess adrenaline administration include hypertension and paroxysmal tachycardia, especially in children. Interestingly, topical application of adrenaline has little effect on blood loss when used for wound debridement (21). Topical thrombin solution (1000 units in 1 ml of saline solution) has been used successfully. It is best applied to limbs before the tourni- quet is released and a pressure bandage is applied for 10min for the thrombin to have maximal action. Larger bleeding points should be controlled with electrocautery (22). Subcutaneous infil- tration of POR-8, a synthetic neurohypophyseal-like hormone has had success (23) but has lost popularity because of the potential complication of supraventricular tachycardia (24). Before applying a skin graft, major bleeding points should be controlled but split skin grafts are them- selves hemostatic and can be applied early.
Other Instruments Developed for Tangential Debridement
Although Humby and Goulian/Weck knives cut in thin slices, it is inevitable that some viable tissue will be removed. This may mean that that some deep dermal partial thickness burns are converted to full thickness wounds. This is because it is difficult to take extremely fine cuts with these instruments, compounded with difficult skin contours and the variable depths of the eschar within the individual wound. In an attempt to minimize the amount of living tissue removed, and because these knives are often not suitable for difficult areas such as digits and
Tangential Debridement 47
FIGURE 2
A Guillian/Weck knife with various guards which allow tissue to be cut between 0.006 and 0.012 inch.
faces including ears, other debridement instruments have been developed. Table 1 shows a com- parison of different debridement instruments.
Dermabrasion
Dermabrasion was first described as a debridement tool for burns in 1963 (25). It is a modification of tangential excision which removes tissue in even smaller increments and in smaller areas than one can with a knife. Advocates claim good results from this technique with less bleeding than with traditional debridement knives with easier access to difficult areas (26). In limited studies, dermabrasion has been shown to facilitate shorter wound healing times and a reduction in scar formation than burns treated with traditional tangential excision (27). The disadvantages of using dermabrasion are that it is generally slower than tangential debridement with a knife, and there is a spray of debrided tissue and fluid from the device which has obvious potential dangers to the- atre staff.
Hydrosurgery
Another advance in the field of tangential excision is the VersajetTMHydrosurgery System (Smith & Nephew, Largo, FL) Fig. 4. (28) The device produces a high powered jet of sterile saline which passes across an operating window and into an evacuation collector. This creates
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FIGURE 3
Deep dermal partial thickness burn to anterior chest before (A) and after (B) tangential excision with dermal preservation (note punctuate beeding). (See color insert.)
a localized vacuum across the operating window by the venturi effect, enabling the target tis- sue to be held and cut, while debris is aspirated from the site. Owing to the ability to debride in small increments, hydrosurgery theoretically can preserve more dermis than conventional tangential techniques with a knife. This suggests that the use of hydrosurgery may be of great benefit in reducing scarring in patients. This may be more important in pediatric burns where hypertrophic scarring and scar contractures are common. Our own use of hydrosurgery has been very encouraging in pediatric burns, and its small cutting surface and fine control is espe- cially useful for the “difficult to access areas” on hands, feet perineum, and head and neck.
Laser Debridement
The CO2laser has been used to debride full thickness burns since 1975 (29). The CO2laser is a photothermal laser with a marked coagulative effect. When used in a series of children with full thickness burns it proved to be very useful at minimizing blood loss, without interfering with graft take (30). Recently, the erbium:YAG laser has shown promising results on partial thickness burns. The erbium:YAG is a photomechanical laser and for this reason has a very limited coagu- lative effect on the target tissue. Because the beam produced has such a strong affinity for its tar- get chromophore it only penetrates a short distance into the skin before its energy is fully absorbed (31).
Tangential Debridement 49
TABLE 1
Comparison of Different Debridement Techniques in Burns
Dermal Fluid and tissue
Technique Speed Bleeding preservation spray Availability
Fascial excision Fast Less than Nil Nil No special
tangential equipment
excision required
Debridement knives Fast 0.40–0.75 ml/cm2 Some Nil Debridement knives
are available in all burn centers Dermabrasion Slow Less than with Maximum Yes Only available in
knife some centers
Hydrosurgery Slow, especially Less than with Maximum Yes Only available in
with early knife some centers
debridement
Laser (YAG) Slow and mainly Less than with Maximum Vapor Only available in
experimental knife some centers
FIGURE 4
The Versajet™ Hydrosurgery System (Smith & Nephew, Largo, FL) being used to debride an ankle burn. (See color insert.)