Burn wound excision and coverage
There are a number of techniques and methods you can use during burn wound excision and coverage. Many are outlined here, along with information on how to evaluate the burn wound after excision, limit blood loss, select donor sites and perform grafting.
Surgical excision techniques and methods
Tangential excision: a sequential approach where you progressively remove thin slices of eschar until only viable tissue remains. You can use a hand-held dermatome (e.g. Weck knife (Goulian knife), Watson knife or Humby knife) or a power-driven dermatome.
Excision to the depth of the fascia: remove the burn wound and subcutaneous tissue to a pre-determined depth, typically to the deep fascia. This technique is recommended when subcutaneous tissue underlying the burn wound is not viable enough to enable vascularization of the skin graft.
Sharp excision: perform with a simple scalpel, a hand-held dermatome (e.g. Weck knife (Goulian knife), Watson knife or Humby knife) or a power-driven dermatome.
Electrosurgical excision: this method coagulates blood vessels to limit blood loss. Use a monopolar instrument.
Hydrosurgical excision: this allows selective removal of necrotic and granulation tissue. The device (Versajet®) is based on the Venturi principle. A jet of water under very high pressure is released into chamber that has an opening on one side, creating a vacuum. Through the opening, non-viable tissue such as softened necrosis and granulation tissue can be taken up from the wound, preserving healthy tissue. The Versajet® Hydosurgery System is widely used to perform hydrosurgery, but it can only be used when resources permit due to the high costs of the disposable materials required. Proper training is advised before using the Versajet®.
Hydrosurgical excision is not suitable for fresh burns with a firm necrosis.
Evaluating the wound bed after burn wound excision
The ability to assess the wound bed post-excision depends on the experience of the clinician. [Is it possible to add something helpful/practical here? How can they evaluate the wound without that experience?]
A well-vascularized, viable wound bed with punctate bleeding is essential for good graft take.
While it is not always possible to remove all necrotic tissue without also damaging essential structures, a skin graft can survive or heal over a small necrotic area by bridging, or it may heal by secondary intention.
Limiting blood loss during and after excision
In order to limit blood loss, infiltrate the burn wound and donor site subcutaneously with a vasoconstrictor and/or a topical hemostatic agent, such as epinephrine solution soaked in sterile gauze.
For limb surgery, you can use tourniquets. Always record the length of time the tourniquet has been applied for.
When the wound is being excised to the level of the fascia, electrosurgery can minimize blood loss.
Other ways to limit blood loss include:
- Topical hemostatic agents such as thrombin and fibrinogen
- Prevention of hypothermia
- Opting for a staged burn excision
- Compression dressings
- Elevating the limb
Options for burn wound coverage
You can achieve definitive coverage in multiple ways, as shown by the reconstructive ladder:
- Direct wound closure
- Split-thickness skin graft (SSG)
- Skin substitutes in combination with a skin graft
- Full thickness skin graft (FTG)
Monitor the patient’s temperature during surgery and be aware of hypothermia. Keep the patient warm with a bottle of lukewarm water (make sure the water is no warmer than this, as it will cause burns), isolation sheet or a bair hugger. Cover the patient’s head to prevent heat loss.
If the temperature drops below 36˚C and you are unable to maintain body temperature, the surgeon should stop the surgery. When body temperature is too low, this can lead to:
- A higher risk of surgical site infection
- Increased transfusion requirements
- Altered drug metabolism
- Adverse cardiac events
There are further options on the reconstructive ladder:
- Tissue expansion – used to cover soft tissue defects and deeper structures
- Tissue transfer – used to cover smaller burn wounds, soft tissue defects and vital, deeper structures
- Local flaps
- Pedicle flaps
- Free flaps
When the burn wound is too large to be covered with an autograft, you can use a skin substitute, such as:
- Human tissue allografts
- Dermal regeneration matrices
- Xenograft-derived temporary wound coverage
- Amniotic membranes
- Cell-based therapies
In a low-resource setting, staged burn excision and conservative treatment are adequate options.
Selecting a donor site for grafting
When selecting a donor site, you should take a number of factors into account, including communication with the patient, the size of the defect, the impact on the donor site, and esthetic appearance.
The most important factor to consider when choosing the location of the donor site is communicating with the patient. You should adequately inform the patient, or their parent or guardian, of the expectations. It is also important to involve them in the decision-making process. It may take some time for the patient to fully understand the principle of skin grafting.
Size of the defect
Adjust the size of the graft to the size of the burn wound. After harvesting a split skin graft (SSG), the graft will shrink in size, and enlargement of a mesh graft is inefficient. In reality, a mesh ratio 3:1 is an enlargement of two times the graft area, and a mesh graft ratio 6:1 is an enlargement of four times the graft area.
Donor site morbidity
After harvesting a donor site, there will be a scar, or at least a change in skin pattern or color. Choose a donor site that the patient can tolerate well – the thigh and the scalp are suitable donor sites in many cases, for example.
When using the scalp as a donor site for patients with hair types VI-VIII, there is a higher rate of complications. Hair types VI-VIII are generally characterized as coiled, very coiled, or zig-zag coiled and are seen more often in people of color. Complications include folliculitis, alopecia and visible hypopigmented scars.
When grafting the face, a good color match is essential. For this area, consider the scalp as donor site and preferably do not use a mesh graft due to the ‘honeycomb’ effect.
Hand-held, electric or air-powered dermatome: good for excising thin strips of skin with a large area and homogenous thickness.
Hand-held knife – use this if there is no power dermatome available and the knives used are like the Humby knife and the Watson knife. There are disadvantages to this method, including irregular edges and the grafts being of variable thickness. The length of the knife also makes it logistically impossible to access and harvest from certain areas of the body.
The Sober dermatome: a low-cost device specially developed for low-income countries. It has a fixed thickness of 0.25 mm (0.001 in).
Determining the thickness
Prior to harvesting the split thickness skin graft (SSG), determine the thickness of the graft; usually a thin graft is used. Adjust the knife or dermatome settings to the preferred thickness, as indicated:
- Thin (Thiersch-Ollier): 0.15-0.3 mm
- Intermediate (Blair-Brown): 0.3-0.45 mm
- Thick (Padgett): 0.45-0.6 mm
Graft expansion – meshing
Meshing of an SSG allows serum and blood to escape from the wound. This minimizes the risk of hematoma or seroma formation, which could compromise graft take. Meshing allows the skin graft to be enlarged, so a small piece of donor skin can cover a large wound.
When using a meshing device, you can select different ratios of meshing (1:1, 1:1.5, 1:2, 1:3, 1:4, 1:6, 1:9). You cannot apply a mesh graft larger than 1:3 to a wound that has been excised at an early stage, as the exposed wound bed in the open areas of the graft will dry out and be prone to infection.
When you use a graft larger than 1:3, use a secondary covering with a meshed allograft (sandwich grafting) to prevent the exposed areas from drying out and protect against infection.
When meshing skin at a ratio of 1:4 or higher, you will need large sheets of split thickness skin, as the mesh graft may become unmanageable. In these cases, if resources permit, a Meek micrograft is preferable to a meshed SSG.
When grafting functional areas such as joints, use a smaller mesh ratio. This is because a larger mesh ratio causes increased scar formation at the recipient site.
For functional areas, use a full sheet graft, meshed with a 1:1 ratio. A mesh ratio of 1:1 provides good drainage and causes less scarring than a larger mesh ratio.
When a meshing device is not available, it is possible to mesh the graft manually with a scalpel, though this is time consuming.
Graft expansion – Meek micrograft
The Meek technique uses a split thickness skin graft cut into squares, which are then further divided into multiple square-shaped islands using a Meek-dermatome. These are then placed onto pre-folded gauzes to achieve a true expansion of 1:9.
This technique is mainly indicated for extensive burn wounds covering a TBSA of >30%, but it can also be used for burns covering a smaller TBSA.
The Meek technique is also indicated if the availability of donor sites is limited, as it requires a smaller donor site to cover the same wound area.
Clinicians need further training to perform a skin graft using the Meek micrograft technique. Read the full technique for more information.
On the first day after the procedure, examine the graft(s) for bleeding or hematoma formation. Similarly to a meshed skin graft, hematoma formation will cause graft necrosis. Once the polyester gauzes are removed after 7-10 days, you can determine the take rate of the graft.
Transplantation and fixation
After harvesting and expanding the skin graft, you can perform the transplantation. Ensure meticulous hemostasis of the wound bed prior to transplantation of the skin graft, as a hematoma formed under the transplant cannot be removed once the graft is fixated, and it will cause graft necrosis.
Perform fixation of the graft using a surgical stapler, which is not time consuming.
Another option is fibrin glue. This negates the need to remove staples, which is advantageous for the patient, especially if they are a child. However, fibrin glue is relatively expensive, so when resources are limited, use (absorbable) sutures.
For areas with a high risk of shearing forces, use a tie over dressing. Also apply a moist dressing, for example Furacin® or Bactroban®, and ensure circumferential contact between the graft and the wound bed.
Donor site management
Ensure good hemostasis of the wound before covering the donor site. Donor sites benefit from occlusion for long periods of time – at least one week, or until healing has occurred. To enable this, use a humid and heat-preserving dressing such as Opsite®, Kaltostat® or Mepilex®.
If these are unavailable, use a moist dressing such as a Vaseline gauze soaked in an antiseptic agent. If the donor site has not healed after the occlusive dressing has been removed, use a topical agent such as SSD or Fusidic acid to treat the open defects.
Re-harvesting of the donor site
You can re-harvest the same donor site once the wound has healed completely and the epithelium appears stable. In practice, re-harvesting is possible after two weeks.
Evaluation of results
Assessment of graft take
The ability to reliably assess the graft take depends highly on the experience of the clinician.
During the process of graft take, the skin graft becomes incorporated into the wound bed and the success of a skin graft primarily depends on the extent and speed at which vascular perfusion of the wound bed is restored. Generally, you can ascertain graft take at day 5-7 by clinical evaluation and assess it by the rate of re-epithelialization.
Recording graft take
Always record graft take as the percentage of successful graft take (i.e. re-epithelialization). A graft is usually deemed successful if clinical evaluation reveals graft take is greater than 80%.
Management of graft infection
If you suspect graft infection, remove the occlusive dressing and continue treatment with topical agents. Evaluate the condition of the wound daily and decide whether to perform re-transplantation.