GENERAL CONSIDERATIONS
The key to surgical intervention in the burn patient is good preoperative planning
in terms of optimal treatment method (see above), prioritization of areas
requiring autografting and the type of skin graft or skin substitute required. It is
best to have the shortest surgical time possible to limit blood loss and hypothermia.
In larger injuries this requires a team of burn surgeons who are experienced
in this type of surgery. Experienced anesthetists are required as these patients
present a challenge in blood volume replacement. An operating room team of
nurses and technicians who have worked in such cases is also invaluable. It is vital
to have blood cross-matched and ready in the operating room before starting any
significant burn wound debridement. A guide to blood requirements is given in
Table 4.2. Perioperative antibiotics are usually required, the choice of which and
duration of treatment are guided by the resident microbiological flora.
TEMPERATURE
The environmental temperature in the operating room must be kept at about
30°C to limit hypothermia and can be achieved by heaters over the operating table.
In addition to the routine hemodynamic parameters measured during surgery,
the patient’s temperature during the procedure and following and the base deficit
on repeated blood gas analysis are useful guides to the patient’s condition and
volume status. A persistent fall in the patient’s temperature to below 35°C is a bad
prognostic sign and should signal the prompt termination of surgery.
PREPARATION OF PATIENTS
Once anesthetized, preparation and skin cleaning of the patient is very important.
In the operating room and under heaters maintaining the environmental
Fig. 4.3. Estimation of burn size—
temperature, all dressings are removed and body is cleaned with warm aqueous
povidone-iodine and the scalp is shaved if burnt or if required for donor site harvest.
Any loose eschar or tissue including previously applied allograft skin is removed.
The areas are then washed down with warm water (37°C) from a selfretracting
hose system. It is important to clean with warm fluids to reduce patient
heat loss. Once cleaned the patient is lifted or log-rolled and all soiled drapes are
removed and replaced by a foam pad with sterile drapes with a shoulder roll to
keep the neck extended.
INSTRUMENTS
The following equipment and instruments are essential for the performance
of burn surgery.
Operating table
Burn surgery can be performed on a standard operating table, but the preference
at our institution is a specially designed table incorporating a lip at the edge
and a drainage hole so that cleaning agents, blood etc., do not run off the table
onto the floor and can be disposed of via the drainage hole and tubing to a drain.
Knives
A variety of knives are required for the excision. Standard surgical 15 and 10
blades are required for sharp excision. Tangential and full thickness excision requires
skin graft knives such as the Braithwaite, Watson or Goulian knives (Fig. 4.4).
The first two skin graft knives are similar and are used for excising large areas on
the trunk and limbs. The Goulian knife is smaller and useful for excision of more
delicate areas such as the hand and face.
Dermatomes
Skin can be harvested using the skin graft knives mentioned above although it
is technically difficult to get consistent, uniform thickness large split skin grafts
with these knives. Most burn surgeons use electric or air driven dermatomes such
as the Zimmer or Padgett to harvest skin grafts particularly if large amounts from
difficult areas are required. The powered dermatomes can be fitted with guards
with widths of 2, 3 and 4 inches to harvest grafts or different widths.
Meshers
These are essential if large areas of wound require covering. There are essentially
two types of machine that can mesh grafts. One type produces a fixed mesh
ratio (2:1, 4:1 etc.) (Brennen Mesher) and if different ratios are required additional
machines are used. The other type relies on dermacarriers or boards to
produce the mesh ratio and thus one machine can produce grafts of differing
mesh ratios using different boards (Zimmer Mesher).
Staplers
Once harvested and applied to the wound (meshed or sheet), grafts require
securing to the wound. They can be secured with dressings, sutures or staples.
Dressings alone used to secure grafts leave them susceptible to shear. Therefore
most surgeons secure grafts with skin staples. Grafts on cosmetically important
areas such as the face tend to be secured with sutures, which are usually absorbable.
Tourniquets
Tourniquets can be used to limit blood loss when excising limb burns. It is
very useful if the tourniquets can be sterilized so that if the whole limb is burnt
the upper part can be excised before application of the sterile tourniquet without
contamination of the operative field. If burns are excised under tourniquet it can
be difficult to determine the exact depth of excision, as there is no bleeding. If the
tourniquets are removed completely, bleeding can be profuse due to reactive hyperemia.
A useful technique is to deflate the tourniquet briefly and apply epinephrine
soaks to the wound, then reinflate the tourniquet after elevation. This
limits blood loss, identifies bleeding vessels in need of hemostasis, and also help in
determining depth of excision by inspection of the wound to see if it bled while
the tourniquet was deflated. To further limit blood loss, skin grafts are then applied
to the excised wounds, a compressive dressing is applied and the limb is
elevated prior to deflation of the tourniquet.
Electrocautery
An electrocautery is essential during burn surgery. In larger burns two, three
or even four may be required. Electrocautery is used for hemostasis and can also be used for full thickness or fascial burn wound excision. Placement of the grounding
plates may be a problem. The soles of the feet can be a useful contact area and
multiple large sterile contact plate coated in contact gel can be placed onto open
wounds or grafted areas as a temporary measure. It is wise to leave a contact plate
attached to the sole postoperatively in case further hemostasis on the ward is
required.
Dermocleisis
Infusion of a weak epinephrine solution (1:1,000,000) under burn eschar can
reduce the blood loss when the wound is excised. Similar infusion subcutaneously
under donor sites (dermocleisis) reduces blood loss and makes skin graft harvesting
easier in difficult sites like the scalp, scrotum, chest wall etc.
Adjuncts for hemostasis
In addition to the above, other adjuncts such as hot saline soaks or weak epinephrine
solutions (1:400,000) applied topically to the excised burn wound reduce
bleeding by stimulating coagulation. Topical thrombin (4-20%) may also be
sprayed onto the wound to help with hemostasis.
TECHNIQUES OF WOUND EXCISION
The technique used to excise the burn wound depends on the factors described
above. In partial thickness wounds an attempt is made to preserve viable dermis,
whereas in full thickness injury all necrotic and infected tissue must be removed
leaving a viable wound bed of either fat, fascia or muscle. In general most areas are
excised with a hand skin graft knife or powered dermatome. Sharp excision with a
knife or electrocautery is reserved for areas of functional cosmetic importance
such as the hand and face.
TANGENTIAL
This technique described by Janzekovic in the 1970s requires repeated shaving
of deep partial thickness burns until a viable dermal bed is reached, which is manifested
clinically by punctate bleeding from the dermal wound bed. The excision is
performed using serial passes of a skin graft knife such as the Braithwaite, Watson
or Goulian or dermatome set at a depth 5-10/1,000 inch until punctate dermal
bleeding is achieved. The more numerous the bleeding vessels in the wound bed,
the more superficial the wound. Hemostasis is obtained with hot soaks and electrocautery
and the wound is ready for grafting.
FULL THICKNESS
A hand knife such as the Watson or powered dermatome is set at 15-30/1,000
inch and serial passes are made excising the full thickness wound. Excision is aided
by traction on the excised eschar as it passes through the knife or dermatome.
Adequate excision is signaled by a viable bleeding wound bed, which is usually fat.
The viability of fat can be difficult to determine but in general viable fat is yellow
and bleeds. Red fat is dead fat, and discoloration of the fat, punctate hemorrhages,
and thrombosed vessels in the wound bed are all indicative of inadequate excision
and necessitate further wound excision. After hemostasis the wound is ready for
grafting.
Full thickness excision can also be achieved using sharp excision with a knife
or with electrocautery. The plane of excision runs between viable and nonviable
tissue, and an attempt is made to preserve viable subdermal structures and fat.
This is used where contour preservation is important such as the face or where
subcutaneous structures such as the dorsal veins in the hand require preservation.
FASCIAL
This technique is reserved for burns extending down through the fat into
muscle, where the patient presents late with a large infected wound and inpatients
with life-threatening invasive fungal infections. It involves surgical excision of the
full thickness of the integument including the subcutaneous fat down to fascia.
This is done with electrocautery and offers excellent control of blood loss and a
wound bed of fascia, which is an excellent bed for graft take.
Unfortunately fascial excision is mutilating and leaves a permanent contour
defect, which is near impossible to reconstruct. Lymphatic channels are excised in
this technique and peripheral lymphedema can be a problem later on.
AVULSION
In some wounds, particularly deeper ones and those treated conservatively,
the necrotic eschar can be avulsed from the underlying viable tissue with minimal
blood loss. This is achieved by applying a heavy pair of tissue forceps to the eschar
and pulling. This technique is usually used in conjunction with fascial or full thickness
excision.
AMPUTATION
Occasionally primary amputation must be considered in management of the
burn wound. It is usually reserved for high voltage electrical injuries or very deep
thermal injuries with extensive muscle involvement and rhabdomyolysis which is
life threatening. In general, limb salvage is attempted if possible with preservation
of length to try and maximize function. Amputation in these cases is reserved for
patients who have an ischemic limb or refractory invasive infection following repeated
debridement. In other circumstances amputation is undertaken only if all
other measures to preserve a useful functioning limb have failed.
WOUND CLOSURE
Following wound excision it is vital to obtain wound closure. Wound closure
is permanent with autologous split skin grafts or temporary using allograft or
skin substitutes. Physiological closure of the burn wound reduces invasive infection,
evaporative water loss, heat loss, pain and promotes wound healing. Temporary
skin substitutes are used to achieve physiological wound closure following
excision until donor sites have regenerated and are ready for harvesting. These
temporary substitutes can be biological. Semibiological skin substitutes can leave
in situ aspects of the skin on a permanent basis such as the dermal portion of
Integra® (see below), but in general all these coverings buy time while the donor
sites heal.
AUTOGRAFT
In general autologous split skin grafts are the gold standard for resurfacing
burns. However they have limitations and attempts are being made to resolve some
of these by the development of skin substitutes. Split skin grafts can be harvested
either as split thickness or full thickness grafts. Full thickness grafts tend not to be
used for acute burns, as the donor sites requires closure, do not regenerate and are
limited. These grafts also require stringent wound conditions to ensure take. Full
thickness skin grafts are extremely useful for postburn reconstruction.
Split skin grafts take more easily, and are the mainstay for wound closure. Split
skin grafts can be harvested either with a hand knife or with a powered dermatome
(see above). Skin grafts can be used as sheet grafts or can be meshed.
ALLOGRAFT SKIN (HOMOGRAFT)
Of all the materials used for temporary wound closure allograft skin is the
most important and its extensive use has been a key factor in improvement in the
mortality associated with extensive burns.
Allograft skin is usually harvested from cadaveric donors after appropriate
donor selection and screening for communicable disease, and consent from relatives
has been obtained. Strict exclusion criteria are applied to ensure safety for
transplantation. Exclusion criteria include any history, physical signs or laboratory
investigation of infection or sepsis, intravenous drug use, neoplasia, hepatitis,
syphilis, slow virus infection, AIDS or HIV, autoimmune disease. Any positive
serologies, evidence of serious illness, death of unknown cause, or toxic substances
within the tissue are also exclusion criteria. Donor age is usually between 16 and
75 years. Skin from refrigerated cadaveric donors should be retrieved within 24 h.
Harvested skin can be either stored fresh in nutrient media at 4°C for up to a
week. If not used the skin is cryopreserved by freezing it in cryoprotectant media
containing glycerol to –196°C in liquid nitrogen. Such cryopreserved skin retains
85% viability of its cells at one year. It is important when thawing cryopreserved
skin to rapidly rewarm it to preserve cell viability. Both fresh and cryopreserved
skin obviously have viable cells within them. Nonviable allograft skin can also be
produced either by preserving it within higher concentrations of glycerol or freezedrying
it. Freeze-dried skin can also be ethylene oxide gas sterilized.
In order of preference of allograft take on the excised burn wound, fresh allograft
is by far the best followed by cryopreserved, glycerolized, then freeze-dried.
When dealing with a sizable wound, the use if viable allograft (fresh or
cryopreserved) is far preferable to nonviable (glycerolized and freeze dried). Nonviable
skin can be useful in the management of smaller wounds when there is
concern about transmission of infectious agents.
Allograft skin is usually harvested, collected, screened, processed, and distributed
by a regional tissue bank. Allograft is analogous to blood, and it is important
to use this vital resource responsibly. When ordering allograft from the tissue bank
it is important to state the type (viable, nonviable, fresh cryopreserved) and amount
of allograft required. The amount can be estimated by determining the body surface
area and burn size in cm2.
Allograft skin can also be obtained from living donors, usually parents or relatives
of burned children. It is usually harvested immediately prior to its use on the
burn victim and is used fresh. In view of the reliable supplies of good quality
allograft skin provided by tissue banks, this method is used infrequently.
Allograft skin can be used either as sheet or meshed graft. It is mainly used
meshed 2:1, and care is taken not to expand the interstices to prevent desiccation,
infection and necrosis of the underlying wound. Meshing the allograft allows any
hematoma and seroma drainage.
Sheet allograft tends to be used to cover cosmetic areas such as the face as even
with unexpanded mesh granulation tissue can grow through the interstices and
leave a permanent pattern.
XENOGRAFTS AND OTHER BIOLOGICAL DRESSINGS
Skin from different species can be used for temporary physiological wound
closure. Porcine skin is commonly used and is commercially available. Its main
use is as a biological dressing for partial thickness wounds. For full-thickness injury
it is not clinically as useful or versatile as allograft and is not generally used
for this indication.
Other biological dressings that have been used mainly on partial thickness
wounds are substances like human placenta and potato skins, which adhere to the
wound, and promote re-epithelialization.
SKIN SUBSTITUTES
Semibiological and synthetic skin replacements are continuously being improved
as investigators try to provide the ideal wound healing environment for
partial thickness injuries, recreate skin by dermal replacement in full-thickness
burns, and attempt to restore epithelial cover by tissue culture techniques. There
are numerous products available and can be differentiated to those that provide
temporary wound cover while the underlying wound re-epithializes or is ready
autografting (i.e., Biobrane®, Dermagraft TC®) and those that close the wound
and help reconstitute part of the resultant skin (Integra®).
BIOBRANE®
Biobrane® is a bilayered material made up of a nylon mesh impregnated with
porcine collagen which has an outer layer of rubberized silicone sheet attached to
it. The outer silicone layer is permeable to gases but not to fluids and bacteria and
thus acts like an epidermal layer. Biobrane® can be used for either partial or full
thickness burns. In partial thickness burns Biobrane® is applied to a clean viable
burn wound and adheres to it allowing rapid re-epithelialization and decreased
pain. After excision of full-thickness wounds, application of Biobrane® can close
the wound temporarily giving donor sites a chance to heal. In both situations
Biobrane® is very susceptible to infection. Purulent exudate can rapidly accumulate
under the Biobrane® and can spread so adherence is lost under the whole
sheet. This can lead to invasive wound infection and deepening of the wound. It is
vital to apply the Biobrane® to the wound within 24 h of the injury and a concurrent
course of an oral cephalosporin is usually given. Its use in full-thickness injuries
is not as successful as partial thickness injury due to infective problems.
DERMAGRAFT TC®
Dermagraft TC® is a bilayered, temporary skin substitute, which contains biologically
active wound healing factors that are in contact with the burn when applied
in addition to an external synthetic barrier. The active wound healing factors
are fibronectin, type I collagen, tenascin, glycosaminoglycans and a variety of
growth factors including transforming growth factor β. This product has been
used for immediate closure of clean mid-dermal to indeterminate burn wounds.
It is applied in a similar fashion to Biobrane® to a viable clean wound bed and
following adherence promotes re-epithelialization. Recent clinical studies have been
promising. It has no role in management of the full-thickness burn.
INTEGRA®
Integra® is an acellular bilaminar device that is designed to provide permanent
wound closure that replaces dermis. It is made up of a disposable upper layer
of silastic that can control evaporative water loss and acts as a barrier to microorganisms
and is analogous to the epidermis. The lower layer is a crosslinked matrix
of bovine collagen and chondroitin-6-sulfate, which is incorporated into the wound
and becomes a ‘neodermis’.
This technology is used to replace dermis in full-thickness burns in an attempt
to modulate postburn hypertrophic scarring. After excision of the burn the Integra
® is applied to the wound in a similar fashion to autograft (Fig. 4.5). Care is
taken to avoid wrinkles or pleats in the Integra® and it is secured to the wound
with either skin staples or sutures. Nonshear dressings are then applied and 0.5%
silver nitrate soaked dressings are applied to the covered areas on a regular basis to
try and limit contamination, colonization and infection of the Integra® covered
wounds. The Integra® should be inspected daily during this time. Any collections
occurring under the matrix should be aspirated and sent for microbiological culture.
If any purulent material appears under the Integra® or if it becomes
nonadherent, then it should be removed, the underlying wound cultured and the
Integra® replaced with allograft skin.
The collagen/chondroitin-6-sulfate matrix is vascularized by host cells over
the next three weeks or so and the artificial dermis is gradually replaced with a
‘neodermis’ which is pink and flat. No granulation tissue should be seen. When
the ‘neodermis’ looks vascularized and has a healthy pink color, the silastic covering
can be removed and very thin epidermal autografts (2-4/1000 inch), containing
epidermis only can be harvested and applied. This provides epidermal cover
for the ‘neodermis’ and produces permanent wound closure (Fig. 4.6?). The grafts
are susceptible to loss at this stage and 0.5% silver nitrate soaks are applied over a
nonshear dressing.
Integra® has been extensively studied and has produced encouraging results
both in single center studies and in a multi-centered randomized controlled trial.
Studies have reported less hypertrophic scarring with a much more pliable resultant
scar and a reduced requirement for secondary reconstructive procedures.
ALLODERM®
De-epidermalized de-cellularized sterile human dermis (Alloderm®) can be
used as a dermal replacement both acute care and for postburn reconstruction. In
acute cases after excision and preparation of the wound bed. Alloderm® can be
applied to the wound with a thin (epidermal) split skin graft applied over it. This
bilayered construct is then secured with staples or sutures and is essentially treated
as a skin graft. This technique is susceptible to epidermal graft loss due to either
desiccation or infection, as the dermal portion of the sandwich must be
revascularized first. Its success in the management of acute burns has been variable
but, it has been successful in postburn reconstruction following contracture
release. It also has been useful in soft tissue augmentation.
CULTURED EPITHELIAL AUTOGRAFT (CEA)
Using tissue culture techniques, epidermal cells (keratinocytes) can be grown
in a laboratory and then used to assist wound closure. From a 1 cm2 biopsy enough
cells can be cultured in approximately 3-4 weeks to cover 1 m2 body surface area.
These cells can be cultured commercially for patients with large burn injuries
however the cost is significant.
This technique only produces the epidermal layer for wound closure and although
there have been many reports of successful use of CEA to close burn wounds
a number of problems limit their use. The lag time of 3 weeks from biopsy to
production of adequate quantities allows wound colonization and granulation
tissue to develop leading to low take rates compare to split skin grafts. Once applied
the grafts are very fragile and often-prolonged immobilization of the patient
is required. Even after successful take the grafted areas remain fragile and blister
easily due to poor and delayed basement membrane formation.
Attempts to overcome some of these problems have been to graft the CEA
onto an allograft dermal bed as described by Cuono in 1986. Initially after wound
excision, allograft is used for temporary wound closure while CEA are produced.
When ready the epidermal portion of the engrafted allograft is removed using a
dermatome or dermabrasion leaving a viable dermal allograft bed behind onto
which the CEA are applied.
This technique has been reported as having better CEA take with improved
basement membrane formation and less fragility and blistering.
In general the use of CEA should be reserved for patients with massive burns
(> 90%) with extremely limited donor sites or major burns where donor sites are
limited, difficult to harvest and cosmetically and functionally important (face,
hands feet, genitalia). A recent review of patients at our institution surviving massive
burn injury showed that patients treated with CEA had a longer hospital stay,
required more operations and had a higher treatment cost compared to a comparative
group of patients treated with conventional techniques.
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