Skin Grafts and Flaps Notes

Burns And Skin Grafting

Burn wounds are one of the most enigmatic and challenging injuries in the medical field. It can vary from small wounds such as sunburn which heal without a trace to larger ones which disproportionately.

Read And Learn More: General Surgery Notes

• Cause initiation of systemic inflammatory response and could lead to immune compromise, multiorgan failure, and often death. The ones who survive major burn injuries are frequently left scarred and crippled.

Elicit documents and present history in a case of burns and perform a physical examination. Describe the pathophysiology of burns.

Epidemiology

A burn is defined as an injury to the skin or other organic tissue primarily caused by heat, radiation, electricity, friction, or contact with chemicals.

• Heat burns occur when some or all of the different layers of cells in the skin are destroyed by contact with a hot liquid (scald), a hot solid (contact burn), or a flame (flame burn).
• Skin injuries due to ultraviolet radiation, radioactivity, electricity, or chemicals, as well as respiratory damage resulting from smoke inhalation, are also considered as burns.
• The majority of these injuries occur in low- and middle-income countries, with almost half occurring in the South-East Asia Region.
• In India, around 7 million people suffer from burn injuries each year with 1.4 lakh deaths and 2.4 lakh people suffering with disability.
• India has one of the highest incidence of burns in the world. Women and children are the victims about 80% of the time (4 out of 5 victims).
• Survival following burn injury has significantly improved over the last several years with the introduction of a multidisciplinary approach and early aggressive fluid resuscitation.
• Use of effective topical antimicrobial agents, and most importantly the practice of early burn wound excision and wound cover. However, extensive burn injuries remain potentially fatal.

Epidemiology Classification

Based on causative agent

1. Thermal
   • Moist heat (scalds)
   • Dry heat (flame burn and contact burn)
2. Electrical
3. Chemical
4. Cold (frostbite)
5. Ionizing radiation

Based on the depth of the burn

1. First degree—involves only the epidermis
2. Second degree—involves varying thickness of the dermis
3. Third degree—involves the epidermis, dermis, and subcutaneous tissue
4. Fourth degree—including fascia, muscles, or bones

Pathophysiology Of A Burn Wound

Jackson’s description of the three zones of injury of the burn wound:

• The zone of coagulation is at the center of the wound where no viable cells remain.
• Surrounding it is the zone of stasis, characterized as a mix of viable and non-viable cells, capillary vasoconstriction, and ischemia.
• This area represents the zone ‘at-risk’ and may convert to necrosis with hypoperfusion, desiccation, edema, and infection. With proper wound care management and fluid resuscitation, however, these changes may be reversed.
• The periphery of the burn wound is the zone of hyperemia, with viable cells and vasodilation mediated by local inflammatory mediators. Tissue in this zone usually recovers completely unless complicated by infection or severe hypoperfusion.

Burn Shock

Shock is an abnormal physiological situation resulting in insufficient delivery of oxygen and nutrients to tissues and removal of cellular waste products secondary to inadequate intravascular blood volume.

• Thermal injury results in a massive shift of fluid from the vascular compartment to the interstitial compartment causing a fall in blood pressure and hence shock.
• Burn injury releases several inflammatory mediators (histamine, prostaglandins, thromboxane, kinins, etc.) which increase the microvascular permeability and alter cell membrane function which favors a fluid shift from blood vessels to the interstitial compartment.

Emergency Management

• Burns patients must be considered trauma victims and Advanced Trauma Life Support (ATLS) protocols must be used in their evaluation.
• Airway, breathing, circulation, disability, and examination for major associated injuries such as head injuries, chest injuries, abdominal injuries, and fractures must be looked for.
  • A—Airway
  • B—Breathing
  • C—Circulation
  • D—Disability
  • E—Examine for associated major injuries

Emergency Management First Aid

• Put out the flame!
  • Make the victim roll on the ground
  • Apply a thick wet blanket
  • Using water or fire extinguishers
• Remove the source of injury, such as clothing unless stuck to the skin.
• Remove items prolonging the injury
• Remove jewelry, belts, and other restrictive items.
• Cooling injured areas with running water.
• Gentle cleansing of the affected area of dirt and soot

Describe clinical features, diagnose the type and extent of burns, and plan appropriate treatment.

Clinical Evaluation

Extent of Burns

• The extent of body surface area involved is one of the most important indicators of mortality independent of the depth of injury.
• Some of the most commonly used methods to clinically estimate the total body surface area (TBSA) burned are:

1. Wallace’s rule of 9.

2. Lund and Browder chart.

• Wallace’s rule of 9 is the simplest and most commonly used formula. It delineates the body surface area into anatomical regions as multiples of 9 and genitalia as 1%.
• Lund and Browder’s chart is a more accurate formula as the difference in body proportions of children and adults are taken into consideration.

Relative percentage of body surface area (% BSA) affected by growth

Depth of Burns

• The depth of the burn is the main factor influencing the ability of the wound to heal itself, as the greater depth of injury will result in fewer surviving dermal and epidermal elements to initiate healing and regeneration.
• Thus it is important in deciding on wound management and whether or not to intervene surgically.

The depth of the burn wound is classified as follows.

1. First degree—superficial burn involving only epidermis
2. Second degree
   • Superficial dermal
   • Deep dermal
3. Third degree–full thickness of skin including subcutaneous tissue
4. Fourth degree—involving muscles and bones

The depth of injury depends on:

• The temperature of the causative agent
• Duration of contract

Superficial or first-degree burns involve only the epidermis. It forms erythema, edema, and a burning sensation. Heals in about 5–7 days.

• Partial thickness burns involve the entirety of the epidermis and a portion of the dermis. Partial-thickness burns are further divided into superficial and deep partial thicknesses based on the depth of dermal injury.
• Superficial and deep partial-thickness burns differ in appearance, ability to heal, and potential need for excision and skin grafting.
• Superficial partial-thickness burns are typically pink, moist, and painful to touch. These burns will typically heal within 2 weeks and generally result in minimal scarring.
• Deep partial-thickness burns involve the entirety of the epidermis and extend into the reticular portion of the dermis.

These burns are typically dry and mottled pink and white in appearance and have variable sensations.

• If protected from infection, deep partial thickness burns will heal within 3 to 8 weeks, however, typically with scarring and possible contractures.
• Therefore, if it appears that the wound will not be completely re-epithelialized in 3 weeks’ time, operative excision and grafting are recommended. Full-thickness burns involve the epidermis and the entirety of the dermis.
• These wounds are brown-black and leathery, and they are usually insensate and do not blanch. Full-thickness burns are best treated by excision and grafting.

Resuscitation

• Secure a good 4 access.
• For major burns, the central venous line is preferred.
• Fluid resuscitation: Various formulas are used for calculating fluid requirement in burns. They include Muir and Barclay, Evans, Brooks, etc. Commonly used is Parkland’s formula.
• According to Parkland’s formula, total fluid for the first 24 hr is 4 ml × body weight (kg) × % of total body surface area burned (TBSA)
  • Half of the calculated fluid was given in the first 8 hours
  • The next half given in the next 16 hours
  • Important to maintain a good urine output of 0.5–1 ml/kg/hr

Only crystalloids are used during the first 24 hours. Fluid calculation should start from the time of burn and not from the time of arrival to the hospital.

• Colloids are not necessary as it is not retained in the circulation during initial period.
• Adequacy of fluid resuscitation is assessed based on monitoring of pulse, blood pressure, and signs of dehydration. A better method is monitoring hourly urine output central venous pressure (CVP).

Care of Burn Wound

• Assessment of area and depth of burn. Look for circumferential deep burns on the extremities or chest which may cause a tourniquet effect resulting in vascular compromise or breathing difficulty as the case may be.
• In case of a circumferential deep burn, emergency escharotomy (release of dried necrotic burn tissue) may be needed.
• Dressing with topical agents: An ideal topical agent must be bactericidal have broad spectrum coverage, be nontoxic, be easy to apply, should penetrate deep into the eschar, and should not cause any metabolic disturbance. But no such ideal agent is available. Commonly used agents are:
  • Silver sulfadiazine
  • Silver nitrate gel or solution
  • Fucidic acid, etc.
• Over the topical agent, cotton pads and bandaging are applied.
• Biologic dressings give temporary covering for the wound alleviating pain and protection from infection, for example.
  • Collagen
  • Amniotic membrane.

Surgery of Burn

Early burn wound excision and cover with autograft or allograft is preferred to reduce morbidity and mortality. At a time, 15–20% of burn wounds can be excised.

• Adequate blood should be arranged for surgery. Debridement can be full-thickness excision or tangential excision depending on the depth of burn. When the burn wound is large, meshed skin grafts are used to cover a wider area.
• In the absence, of adequate autografts skin substitutes like cultured epithelial autografts (CEA), synthetic skin substitutes (Example. Integra, Biobrane), or skin allografts may be used.

Other supportive measures:

• Good analgesia, for Example. morphine, paracetamol, NSAIDs
• Anti-histamines for decreasing histamine-induced adverse reactions
• Gastroprotection: Against Curlings ulcers (Example. PPIs such as pantoprazole)

Nutritional Support for Burn

Forms an important feature of effective burn patient management. Hypermetabolism occurs following the injury and the diet should accommodate for the higher carbohydrate and protein requirements.

This increased metabolic rate begins immediately following injury and can go up to 150 to 200% of normal and persists until complete wound coverage is achieved.

The hypermetabolism may extend for months thereafter. Oral feeding should be encouraged and started early. For those who do not tolerate oral feeds, nasogastric tube feeding may be given.

Curreri formula for calculating calorific requirement:

Adults: 25 kcal × weight (kg) + 40 kcal × % TBSA

Protein requirement:

• 2 g × kg body weight per day
• Supplements such as vitamin A, vitamin C, zinc, omega-3 fatty acids, glutamine, iron, etc. are also given routinely.

Burn Wound Infection

• Early burn wound is sterile due to the thermal effect. Contamination of the wound occurs either from the environment or by opportunistic pathogens from the patient’s own body.
• Infection remains a significant risk following burn injury. Burn patients are also immunocompromised for a number of reasons.
  1. Loss of protective skin barrier
  2. Cellular and humoral portions of the immune response are compromised.
  3. Hypoproteinemia → Decreased production of antibodies
  4. Impaired chemotaxis and phagocytosis

Infection can be bacterial, fungal, or viral. Most often the infection is by bacteria and that too aerobic organisms. Common gram-positive infections are by Staphylococcus species, streptococci, and enterococci.

1. The majority of gram-negative infections are due to Pseudomonas species. Others include Acinetobacter, E. coli, Klebsiella, etc. which are often multidrug resistant.
2. Prophylactic antibiotics are not advisable for minor burns with early presentation. For major burns, all attempts should be made to remove them.
3. The necrotic tissue under cover of broad-spectrum antibiotic after attaining hemodynamic stability. Tissues are taken for bacterial culture at the time of initial debridement.
4. Following the initial 72 to 96 hours, periodic cultures are important in making a diagnosis of infection. Temperature spikes warrant culturing of wounds, urine, blood, and central lines. The selection of antibiotics should be based on culture results.

Burn Inhalation Injury

Inhalational burns are devastating and increase the mortality of burn victims by 20% independent of other factors.

Scenarios of Burn

• Burns sustained in closed space
• Explosions
• Facial burns
• Prolonged exposure to flames

Suggestive Clinical Features of Burn

• Facial burns with singed facial and nose hair
• Inflamed and oedematous mucosa
• Sooty dark sputum in the mouth or nostrils
• Hoarseness or Stridor
• Labored breathing

They may have inflamed airways or damaged lung tissue. May require intubation or tracheostomy.

Management of Burn

• Oxygenate—high flow O₂
• Establish and maintain a patent airway. Intubate or perform tracheostomy early, if necessary.
• Obtain ABGs and blood CO levels, if possible.

Patients are predisposed to ARDS and pneumonia and may require aggressive treatment in the form of:

1. Chest physiotherapy
2. Pulmonary toilet
3. Bronchodilators
4. Intubation and mechanical ventilation
5. Sputum or bronchial lavage-based antibiotic therapy.

Complications of Burns

Early

• Shock, renal failure, wound infection
• Septicaemia
• ARDS, pneumonia
• Multiorgan failure

Late

• Scarring
• Contractures

Contractures

Contractures Definition

Wound contracture is a process that may occur during normal wound healing. When there is an excess wound contraction—an abnormal healing process—leads to physical deformity characterized by skin contraction and functional limitations.

Goals of management:

1. Maximize function
2. Minimize disfigurement
3. Restore appearance

Timing of surgeries for contracture:

• The exact timing of surgery is tailored to each patient’s circumstances.
• At least 3 months post-wound cover so as to attain adequate tissue equilibrium.

Contracture prevention and non-operative scar treatments:

1. Early and aggressive mobilization therapy with active and passive range of motion (ROM) exercises
2. Splints across joints
3. External pressure garments
4. Silicone gels and gel sheets
5. Intralesional triamcinolone injections
6. Laser resurfacing

Surgical interventions to minimize scar and contracture. Reconstructive options after excision or release of contractures are:

1. Direct closure: If there is minimal tension across the wound
2. Serial excision
3. Skin grafts: Partial thickness grafts and full thickness grafts
4. Local flaps and tissue adjustments, such as Z-plasty
5. Tissue expansion
6. Distant flaps and free tissue transfer.

Electrical Burns

The passage of electricity through the tissue generates heat depending on the tissue’s resistance. Low-tension injuries are usually localized. High-tension injuries can be devastating due to the damage caused in-depth than on the surface.

Electrical burn can be:

• Direct contact burn
• Arc burn (current passes from a source to an object)
• Flash burn (similar to thermal burn)

Patients with electrical burns can develop cardiac, renal, and neurological complications.

• In the extremities can cause compartment syndrome which will require early fasciotomy.
• Electrical burns may have associated injuries like fractures following falls secondary to electric shock.

Resuscitation formulas may not be adequate as the extent of injury in the depth cannot be accurately assessed clinically. In the absence of myoglobinuria or hemoglobinuria.

• A urine output of 30–50 ml/hour should be maintained with Ringer lactate solution. Higher urine output of 1–2 ml/kg body weight is necessary when associated with myoglobinuria.
• After hemodynamic stability, all the devitalized tissues are debrided which may need multiple stages and reconstruction with skin grafts or flaps.

Chemical Burns

Chemicals cause irritation and destruction of tissues by different chemical reactions when in direct contact. The severity of a chemical burn is determined by:

• Concentration of the chemical
• Duration of contact with the tissues
• Quantity of the chemical
• Mechanism of action

They act as oxidants, reducing agents, corrosives, protoplasmic poisons, vesicants, or desiccants. Common chemical burns are caused by acids or alkalis. The latter causes more damage due to liquefaction necrosis, whereas acids act by coagulation necrosis.

• The principles of management of chemical burns involve the removal of all offending agents from the patient’s body. The involved part is thoroughly washed under running tap water for ½ to 1 hour.
• When a burn occurs with chemical powder, it should be dusted off first before irrigation. The use of neutralizing agents is controversial.
• Special mention is necessary for hydrofluoric acid. It continues to destroy the tissues in the depth until comes in contact with bone. It can cause severe calcium deficiency which may be lethal.
• Local application of calcium gluconate gel, or subcutaneous or intra-arterial calcium gluconate injections may be used as an antidote.

 

Friction Burn

• Results due to rubbing of the skin against a rough surface. The most common cause is road traffic accidents. Other causes include sports injuries and falls from height.
• Superficial injuries can be treated conservatively. Deeper wounds may need tangential excision or full-thickness excision and skin grafting.

Skin Bank

• Skin harvested from cadavers can be stored at 4–8°C for prolonged periods in skin banks (tissue bank). Banked skin allografts are widely used nowadays for the management of major burns.
• Like other organ donations, skin also can be donated to save burn victims or patients with major skin loss. Being a temporary procedure, skin allotransplant does not need tissue matching. It has reduced the mortality and morbidity in burn patients considerably.

Free Skin Grafting

Skin grafting is the most common method of achieving wound cover.

Free Skin Grafting Types

1. Split Skin Graft (SSG-Thiersch Graft)

• Also called partial thickness graft.
• Consists of the epidermis and a variable portion of the dermis.
• Split skin graft is usually harvested using Humby’s knife. Drum dermatome or a power dermatome may also be used.
• The preferred donor area is the thigh.

2. Full Thickness Graft (Wolfe Graft)

• Consists of the epidermis and the full thickness of the dermis.
• Harvested using an ordinary scalpel.
• Needs excellent vascularity of the recipient wound for graft survival.
• Used for small uncontaminated wounds produced after excision of skin lesions or after release of skin contractures (lower eyelids, fingers).
• The donor area needs primary suturing or split skin graft for healing and hence limits the size of the graft.
• Unlike split skin grafts, full-thickness grafts do not contract and retain their color. Hence, they are cosmetically superior.

Indications Of Skin Graft

Ideal Requirements for Free Skin Graft

• The wound should be free from infections such as streptococci and pseudomonas
• Vascular wounds, for Example. wounds with healthy granulation
• The wound should be thoroughly debrided
• Hemostasis must be achieved before placing the graft
• Close and immobile contact between the graft and the wound
• The recipient area should be immobilized with a POP slab

1. Skin loss

• Post-traumatic (Example. avulsion and degloving injury)
• Post-surgical (Example. excision of tumors, excision of burn wound)
• As a result of pathological process (For example. venous ulcer, diabetic ulcer)

2. Mucosa loss

• After excision of lesions of the oral cavity, tongue.
• For resurfacing reconstructed vagina in cases of vaginal agenesis.

Contraindications For Skin Graft

Infection by beta-hemolytic streptococci. They produce fibrinolysin which dissolves fibrin.

• Presence of an infected wound with copious discharge in the vicinity.
• Avascular wounds: Exposed bare bone without periosteum, exposed tendon without paratenon, and exposed cartilage without perichondrium.

Healing Of The Donor Area

The donor area of a split skin graft heals by epithelialization from the adnexal remnants of the dermis, pilosebaceous follicles, and or sweat gland apparatus. Complete healing of the donor area occurs in 8–10 days.

The Process Of Graft ‘Take’

The processes that result in reattachment and revascularisation of the graft to the bed are collectively referred to as the “take” of graft.

• The graft initially adheres to its new bed by fibrin. Revascularisation starts in 48 hours and is completed by 4–5 days. This is achieved by the outgrowth of capillary buds from the recipient area to unite with those on the deep surface of the graft.
• For the first 2 days after grafting, the skin graft derives its nutrition from the wound by the process of serum imbibition or plasmatic circulation.

FLAPS

A flap is a block of tissue transferred from the donor to the recipient area along with its vascularity.

Common Indications For Flap Surgery

To cover defects or wounds where free skin graft cannot be used, for Example. exposed bare bones, bare tendons, bare cartilage.

• Wounds with exposed joints exposed major vessels and nerves.
• Implant exposure following orthopedic procedures.
• In wounds with soft tissue loss, future reconstructive surgery is contemplated.
• Defects that need better contour to improve cosmesis.
• Breast reconstruction following mastectomy.

Classification Of Flaps

These are broadly classified into pedicled flaps and free flaps.

1. Pedicled Flaps

The pedicle or the base remains attached to the donor site during its transfer to the recipient area. Pedicled flaps may be of the following types:

1. Local flaps, Example. rotation, transposition, limberg and bilobed.
2. Pectoralis major myocutaneous (PMMC) flap, deltopectoral (DP) flap for head and neck defects, transverse abdominis myocutaneous (TRAM) flap for breast reconstruction.
   • Regional flap, Example. PMMC, DP for head and neck defects,
   • TRAM for breast reconstruction.
3. Distant flaps, for Example. groin flap, and subaxillary flap for hand defects. A few examples of the pedicled flap
   • Skin flap
   • Fasciocutaneous flap
   • Muscle flap
   • Myocutaneous flap
   • Adipofascial flap
   • Osteocutaneous flap

2. Free Flaps

These are completely detached from the donor area before being transferred to the recipient area. The vascularity of the flap at the recipient site is immediately restored by anastomosing the vessels of the flap with the vessels at the recipient area using microvascular techniques.

Some Of The Commonly Performed Flaps

• Forehead flap: Entire forehead skin can be raised based on an anterior branch of the superficial temporal artery. It bears an unsightly scar from the donor site. A median (Indian) forehead flap based on supratrochlear vessels is a very useful flap in reconstructing defects over the nose.
• Deltopectoral (DP) flap: It is supplied by the upper 4 perforating branches of the internal mammary artery and is used to reconstruct defects of the neck and face. After about 4 weeks, the flap is divided, and the wall is.
• Pectoralis major myocutaneous (PMMC) flap: The pectoral branch of the thoracoacromial artery is the pedicle of this flap. It is the ideal pedicled flap for the reconstruction of head and neck defects following ablative surgeries for various head and neck cancers.
  • Hence, it is described as a workhorse among the flaps. Osteomyocutaneous PMMC flap including the 5th or 6th rib can be used for mandibular reconstruction.
• Latissimus dorsi flap (LDF): As a myocutaneous flap, based on thoracodorsal vessels can be used for reconstruction of the lower half of the face, neck, breast, chest wall, axilla, and upper arm.

Free (Microvascular) Flaps

Using an operating microscope and microvascular techniques, it is possible to do a free tissue transfer of tissues such as skin, muscle, bone, intestine, omentum, etc.

• The procedure involves anastomosis of vessels of the flap to vessels at the donor site, for Example.
• latissimus dorsi muscle myocutaneous flap, radial artery forearm flap, gracilis flap, and free fibula flap.

Miscellaneous

Skin Substitutes

• This is one of the important requirements wherein the large surface area of burns and skin is lost.
• An ideal substitute must be affordable, permanent, provide normal pigmentation, resist scar formation, and grow with developing children.
• A few examples of skin substitutes are:
  • Dermal substitutes: They allow for the creation of a ‘new dermis’. They are formed from the patient’s own mesenchymal cells. Once the ‘neo-dermis’ is formed, a split-thickness skin graft is applied. Thus, the site of the burn is closed quickly with less scarring.
  • Cultured epithelial autograft is another example of a dermal substitute. They are cultured from the patient’s own full-thickness biopsy. It will require 3 weeks to grow.
  • Another cultured skin is a biological dressing from cultured neonatal keratinocytes and fibroblasts. They are all very expensive.

Hydrotherapy in Burns

It refers to the usage of external water (which may be very cold) to run over the burned part for a few minutes. Methods used are:

1. Immersion hydrotherapy: It is performed in tubs called hydrotanks or burns tanks. Tanks should be disinfected after usage. The water used is sterile.

2. Shower hydrotherapy: Depending upon the severity of the burns, the shower can be either in a supine or sitting position. Showering immediately rinses away dead skin and bacteria.

How does it work?

• Cleans the surface of a wound and removes debris
• Removes pus
• Prevents loss of fluid through skin
• Minimises scar formation
• Provides a moist environment for wound healing
• Minimises risk of infection
• Duration
• It may vary from 10 to 20 minutes
• Sedation
• Sedation or general anesthesia is required as it can be very painful.

Discuss the medicolegal aspects of burn injuries.

1. Antemortem or postmortem burns: Firstly, it has to be determined whether the burns are antemortem or postmortem in origin.

• Features of antemortem burns are:
• Presence of soot (carbonaceous particle) in airways Line of redness surrounding the burn injury Blister with serous fluid rich in protein and chloride

2. Manner of sustaining burns: It can be accidental, suicidal, or homicidal

• Accidental burns: It is the most common variety encountered. It may happen during cooking, careless burning of various forms of waste, firecracker accidents, or any other industrial or domestic accidents.
• Suicidal: Self-inflicted burns. It may be related to dowry (Section 304 (B) IPC). It may also be a form of protest against government (self-immolation)
• Homicidal: It may be done sometimes related to dowry or any other crime related to women. Sometimes a person may be killed by others using fire or any other inflammable substance.
• Scalds: May be accidental commonly. It may be also seen in child abuse cases where it is done deliberately on the child by the adult.
• Electrical burns: It is mainly accidental. Sometimes it may be suicidal which is however rare.
• Lightening burns: It is accidental in nature.