Healing process is extremely painful because this type of wound involves harm to sensory nerves and the wound can easily become infected.

Closed wounds are as dangerous as open wounds. The types of closed wounds are:

· Contusions generally identified as bruises, caused by a blunt force trauma those damages tissue under the skin.

· Hematomas, also called a blood tumour, caused by damage to a blood vessel that in turn causes blood to collect under the skin.

2.2 Open Wounds: This group includes lacerations, cutting-pricking tool wounds, gunshot wounds, surgical wounds and metabolic wounds. Wounds excluding for lacerations effect serious damage to tissues below the skin. In laceration type wounds, skin and subcutaneous tissue have been destroyed, but deep tissues remain healthy. The integrity of tissues anatomy is injured in cutting pricking tool wounds with no any tissue damage at the edges of the wound³.

Open wounds can be classified on the basis of thing that caused the wound. The types of open wound are:

· Incisions wounds created by a clean, sharp-edged object such as a knife, razor, or glass splinter.

· Lacerations, irregular tear-like wounds caused by some blunt trauma. Lacerations and incisions may appear regular) or irregular. The term laceration is commonly misused in reference to incisions.

· Abrasions, superficial wounds in which the epidermis is scraped off. Abrasions are frequently caused by a sliding fall onto a rough surface.

· Puncture wounds is generated by an object puncturing the skin like nail or needle.

· Penetration wounds, caused by an article such as a knife entering and coming out from the skin.

· Gunshot wounds, caused by a bullet or related shot driving into or through the body. There may be two wounds, one at the site of entry and one at the site of exit, generally referred to as a "through-and-through."

3. WOUNDS ARE ALSO CLASSIFIED ACCORDING TO TISSUE LOSS

3.1 Wounds with Tissue Loss: These types of wounds involve damage or loss in some or all of the skin layers. Healing occurs via filling of the wound area by granulation tissue typically growing from the base of a wound. According to tissue loss they are collected in two groups. In superficial wounds, the whole epidermis and papillary layer of the dermis are damaged. In full-thickness wounds epidermis, the entire the layers of the dermis and subcutaneous tissue are also damaged⁴.

3.2 Wounds without Tissue Loss: These kinds of wounds occur as a result of tissue crushing. The severity of bleeding occurring in tissue varies according to the condition of the wound. Tissues exposed to this kind of wound heal after granulation tissue formation in minimal level in first phase of healing process^5.

4. CLASSIFICATION OF BURNS WOUNDS

Burn wound produce when skin or organs are damaged by an electrical current, heat, chemical or flammable agent effect⁶.

Burns can be classified into 4 groups based on depth and the affected skin layers:

4.1 First-degree burns

First-degree burns generally occur as a result of short term heat or flame contact or long-term exposing to intense sunlight. Only the outer layer of the epidermis and Stratum corneum are damaged in this type of burn, and there is no damage in the dermis. First-degree burn areas are characterised by slight oedema. At this stage the skin begins to dry and it heals within a week⁷.

· Limited to the epidermis

· Mild discomfort

· Commonly treated on outpatient basis

4.2 Second-degree burns

These types of burns are deeper than first-degree burns and necrosis spread into the dermis. Damage covers the entire epidermis and some part of dermis. The wound is clinically characterised by pain and erythema. The healing depends on the deepness of skin damage and formation of infection. Generally, second-degree burns repair suddenly in a short period if infection does not occur. If infection occurs in the wound, it can easily convert to third degree burn. The burns in this group may be divided into two categories, termed superficial and deep dermal second-degree burns⁸.

Superficial Second Degree Burns: These occur due to short period contact with flame or hot liquids. Generally, the upper portion of the Stratum germinativum is damaged in superficial second-degree burns. Because of the leakage of liquid plasma from the burned area surface is generally humid. Recovery usually occurs within 3-4 weeks with zero or very mild scarring⁹.

· Involves the epidermis and external part of the dermis

· Often seen with scalding injuries

· Presents with blister formation and typically blanches with pressure

· Sensitive to light touch or pinprick

Deep Dermal Burns: It is occur due to contact with chemicals such as flame, hot liquids or acids, or exposure to high electrical current. In these types of burns, epidermis is completely burned, which is extends to the Stratum germinativum damage and the base section of the dermis. Re-epithelialisation time depends on dermis degradation, the burnt hair follicles amount and sweat glands, and the infected areas width. It generally closes within 2 months if the wound is properly preserved¹⁰.

· Involves the epidermis and the majority of the dermis

· A smaller amount sensitivity to light touch and pinprick than superficial form

4.3 Third-degree burn

These kinds of burns result from hot water, fire and prolonged contact with electrical current. The wound area exhibits tautness and brightness as the elasticity of the skin is lost, causing abnormal shrinkage. In such cases, all structures within the skin sustain damage. The dermis and subcutaneous fat are destroyed as a result of coagulation necrosis. Thrombosis occurs in vessels under the skin. Increased capillary permeability and oedema is much higher in third degree burns than second-degree burns. This event is usually associated with suppuration. Capillary bundles and fibroblasts are organised in granulation tissue under scar. If the burn affects subcutaneous fat, healing can take much longer. Burn affecting the muscle causes increasing in degradation of red blood cells. The care of third-degree burns requires removing scar tissue and covering the wound with a graft. If grafting is not carried out, a thick layer of granulation is shaped and the contraction of the area follows it. At this stage, re-epithelialisation, slightly, occurs on the edge of wound granulation is soft, can be infected and healing continues over several months. Permanent deep scars in the skin occur following healing in these kinds of wounds and surgical intervention is usually required to restore normal appearance¹¹.

· Involves epidermis, and the entire layers of dermis, extended to subcutaneous tissue

· Appears dry, leathery, and insensate

· Can be difficult to differentiate from deep partial-thickness burns

· Usually found when patient’s clothes caught on fire

· Generally require transfer to burn surgeon for skin grafting to heal.

4.4 Fourth-degree burns

Fourth degree burns is a result of high-voltage electric injury or severe thermal burns, which requires hospital admission. This refers to the carbonization of burned tissues (Table 1).

5. WOUND HEALING PROCESS

The wound healing process is a series of independent and overlapping stages. In these stages will both cellular and matrix compounds work to re-establish the integrity of damaged tissue and replacement of lost tissue. These overlapping series can be classified in five stages:

5.1 Haemostasis: the first response to injury is bleeding. Bleeding is an effective way to wash out bacteria that are on the surface of skin. Afterwards, bleeding activates haemostasis stage that is initiated by clotting factors. The clot dries out and creates a hard surface over the wound that protects tissues underlying.

5.2 Inflammation: this stage starts almost at same time as haemostasis. It occurs from between few minutes to up to 24 minutes after injury. In this stage histamine and serotonin are released into wound area and activate phagocytes to enter the wound area and engulf dead cells.

5.3 Migration: in this stage the reestablishment of wound begins. The epithelial cells and fibroblasts move into the injured area and grow rapidly under the hard scab to replace the damaged tissue.

5.4 Proliferation: this stage has three characteristics. First, the granulation tissue is formed by growth of capillaries. Lymphatic vessels enter into wound in to second stage and the third one, synthesis of collagen starts providing form and strength to the injured tissue.

5.5 Maturation: in this stage, the shape of the final scar is determined by formation of cellular connective tissue and strengthening of the new epithelium¹².

6. CAUSES OF BURN

Burns can cause by a broad variety of substance and external sources such as contact with electricity, chemicals, friction, radiation and heat.

6.1 Chemical: Most chemicals that cause chemical burns are strong acids or bases. Corrosive chemical compounds such as sodium hydroxide and sulphuric acid causes chemical burns. Hydrofluoric acid is able to damage to the bone and some time burns not immediately apparent. Depending on time of contact, potency of the material, and other factors, chemical burns can be either first, second, or third degree burns.

6.2 Electrical: Electrical burns are caused by an electric shock. Common occurrence of electrical burns comprises workplace injuries, defibrillated or cardioverted without a conductive gel. Lightning is also a rare cause of electrical burns.

6.3 Radiation: Radiation burns are caused by prolonged exposure to UV light, radiation therapy, sunlamps, radioactive fallout, and X-rays. Most common burn related with radiation is sun exposure, particularly two wavelengths UVA and UVB, the latter being more dangerous.

6.4 Scalding: Hot liquids (water or oil) or gases (steam) causes scalding, it mainly occure from contact to high temperature tap water in baths or showers. When extremity is held under the surface of hot water immersion scald is created, and it is a common typr burn seen in child abuse. A blister is formed in the skin filled with fluid, which is the result of body’s reaction to the heat and the subsequent inflammatory reaction. Top of the blister is dead and the fluid contains toxic inflammatory substances. Normally scald burns are first or second degree burns, but due to prolonged contact it can be third degree burns.

7. PATHOPHYSIOLOGY OF BURN WOUND

The pathophysiology of the burn wound is related to the initial distribution of heat onto the skin, which is a function of both the temperature and the exposure time i.e. a high temperature for a short time may cause the same tissue damage as a lower temperature for a longer time. Three zones of histopathological injury: coagulation, stasis and hyperaemia. The zone of coagulation is comprised of eschar or necrotic tissue and is closest to the heat source. This is surrounded by the zone of stasis, where there is only moderate tissue damage, but slow blood flow and oedema due to capillary leakage and cell membrane disruption. Poor blood flow in this zone may lead to local tissue ischemia and further necrosis. Surrounding the zone of stasis is the zone of hyperaemia, in which cell damage is minimal and blood flow gradually increases resulting in early spontaneous recovery¹³.

7.1 Pathogenesis of Burn Wound Conversion

Burn wound progression is complex and caused by additive effects of inadequate tissue perfusion, free radical damage, and systemic alterations in the cytokine milieu of burn patients, leading to protein denaturation and necrosis. Fundamental inferences, infection, tissue desiccation, impaired wound perfusion, oedema, age and metabolic derangements play important roles.

The pathogenesis of burn wound conversion is related to a multitude of factors, many of which are related to the presence of vasoactive and inﬂammatory mediators in higher-than-normal concentrations. The role of vasoconstriction is also very important in burn wound conversion. Thus an imbalanced ratio of vasodilatory and vasoconstrictive prostanoid can threaten viability of tissue in zone of stasis. Vasodilatation, too, has been implicated. Up-regulation of inducible nitric oxide synthase may produce peripheral vasodilation that sets off an inﬂammatory cascade detrimental to the survival of threatened tissue in the zones of stasis and hyperaemia. Up-regulation of transcription factor nuclear factor results in increased downstream production of many inﬂammatory cytokines. In addition, nitric oxide may react to produce per- ox nitrite, an oxygen free radical that causes additional tissue damage. Free radical injury to the zones of stasis and hyperaemia may be involved in the pathogenesis of burn wound conversion. In the setting of acute burns, neutrophil activation and xanthine oxidase activity generate oxygen radicals such as hydrogen peroxide and superoxide. Concomitant decreases in superoxide dismutase, catalase, and glutathione, α-tocopherol, and ascorbic acid levels impair the body’s antioxidant mechanisms.

Another factor in burn wound progression may be linked to hypo-perfusion secondary to oedema-related ﬂuid shift. Prostaglandins, histamine, and bradykinin increase in-transvascular permeability and promote the passage of ﬂuid in interstitial spaces. As such, local oedema translates into both local and systemic ﬂuid shifts that exacerbate hypo-perfusion in vulnerable tissue, speciﬁcally in the zones of stasis and hyperaemia. Micro thrombosis of viable tissue proximal to frankly necrotic tissue appears to be important. Elevated bradykinin levels not only increase vascular permeability but also act to promote coagulation. In combination with the pro-coagulant properties of thermal energy, bradykinin may stimulate micro thrombosis in the zone of stasis and, as such, contribute to the progression of superﬁcial burns to deeper ones¹⁴.

8. FACTORS AFFECTING BURN WOUND CONVERSION

8.1 Local Factors

Several factors act locally to predispose partial thickness burns to progress to deeper wounds. Most notable are infection, tissue desiccation, collateral wound oedema, and circumferential Escher in the extremities. Bacterial infection contributes to the process and is decreased by topical antimicrobial agents. In a retrospective study of 342 patients with 10%–50% total-body-surface-area burns, demonstrated that topical 1% silver sulfadiazine decreased both the conversion rate and the healing time of deep partial-thickness burns. The bacterial load of predominant surface microorganisms, speciﬁcally Staphylococcus aureus, Pseudomonas species, and Klebsiella species, was also decreased. Silver-coated barrier dressings have also been shown to be effective in burns closed with cultured skin substitutes (Table 2).

Oedema, desiccation, and circumferential eschar are local factors that increase rate of burn wound progression by decreasing tissue perfusion. Local hyperaemia and desiccation compromise perfusion via shifts in intravascular and interstitial ﬂuid volumes. Both processes decrease intracellular ﬂuid volumes, altering homeostasis in a manner that ultimately decreases intravascular volume and inhibits oxidative metabolism of partially burned tissue. Circumferential eschar in the extremities acts mechanically, compromising distal tissue perfusion when escharotomy is delayed¹⁵.

8.2 Systemic Factor

Systemic factors can be considered as those that impair wound perfusion, those that predispose to infection, those related to metabolic derangements, and those that are related to general health status. Impaired wound perfusion often occurs secondary to shock, hypoxia resultant from pulmonary insufficiency, and massive wound sepsis. Conversion of partial- to full-thickness burns is hastened when ﬂuid resuscitation fails to provide adequate ﬂux, or perfusion, to burn wound (Table 3). Similarly, restoring and maintaining perfusion pressures maximally oxygenates injured and non-injured tissues and, as such, promotes spontaneous healing while minimizing wound conversion and bacterial colonization¹⁶.

9. BURN WOUND MANAGEMENT

Injuries caused by severe burn injuries result in significant disability and death. The final aim of burn management and therapy is wound healing and epithelisation as soon as possible in order to prevent infection and to reduce functional aesthetic after use. The goal of burn treatment is to provide the most rapid possible healing of surface burns and to speed up the surgically provided restoration of lost skin in deep burns. The local conservative treatment of burn injuries is of major importance. Treatment of patients with superficial damage is always conservative. In deep burns, local treatment is used to prepare wounds for surgery and to create conditions for the non-rejection of auto dermotransplants and full-thickness grafts. Recent advances in clinical care have reduced morbidity and mortality. A wide variety of preparations and remedies of non-organic, organic, biogenic, and phytogenic origin have been devised and used in the topical treatment of burns¹⁷.

9.2.2 Topical Antimicrobial for Burn Wound

Topical antimicrobial preparations have been particularly applied to prevent and treat burn infections compared to other traumatic, surgical and medical indications which could be susceptible to infection. Many of the agents are designed to be used prophylactically to prevent infection developing, while others are designed to kill the actually microbial cells that are proliferating within the burn when an infection has developed (Table 5). Many of these topical agents are applied onto the surface of the burn, if they are designed to be actively microbicidal, consideration must be given to the degree which the agents will penetrate into the burned infected tissue to reach the microbial cells that have invaded23,24. We can measured the extent to which several agents (gentamicin sulphate, mafenide acetate, nitrofurazone, povidone-iodine, silver nitrate, and silver sulfadiazine) penetrated through burn eschar^25,26,27.

Table 5. Antimicrobial agents used in burn care

S.no.	Antimicrobial agent	Antimicrobial coverage
1.	Bcitracin (Bacillus subtilis)	Gram + bacteria
2.	Polymyxin B sulphate (Bacillus polymyxa)	Gram - bacteria
3.	Neomycin and other aminoglycoside (Streptomyces fradie)	Gram + bacteria
4.	Mupricin(P flourescens)	Anti MRSA
5.	Nystatin (Streptomyces noursei)	Antifungal
6.	Mafenide acetate	Broad spectrum antibacterial
7.	Neosporin	Broad spectrum antibiotic
8.	Nitrofurazone	Gram+, Gram-
9.	Povidone iodine	Gram +,Gram-, yeast
10.	Gentamicin	Gram -
11.	Clotrimazole	Yeast, Fungi
12.	Xeroform	Gram+, Gram -,yeast
13.	Repithel	Gram+,Gram -,Yeast
14.	Scarlet red	Gram +, Gram -
15.	Ciclopirox	Yeast, Fungi
16.	Chlorhexidinedigluconate	Gram+, Gram-Yeast, Fungi

9.2.3 Antimicrobial peptide (AMP)

The term antimicrobial peptides refer to a large number of peptides found among all classes of life possessing both antibacterial and antifungal activities. They have been shown to kill Gram-negative and Gram-positive bacteria (including strains that are resistant to conventional antibiotics), mycobacteria (including Mycobacterium tuberculosis), enveloped viruses, and fungi. Besides acting as endogenous antibiotics AMPs also participate in multiple aspects of immunity ^28,29,30. So unlike the majority of conventional antibiotics the antimicrobial peptides also have the ability to enhance immunity by functioning as immuno-modulators. AMPs are divided into heterogeneous groupings on the basis of their primary and secondary structures, their antimicrobial potential, their effects on host cells, and the regulation of their expression. Most AMPs are small (12–50 amino-acids), have a positive charge and an amphipathic structure that enables them to interact with bacterial membranes. AMPs have a higher affinity for microbial membranes compared to the membranes of host cells and therefore preferentially lyse the pathogenic, microorganisms^31,32,33.

9.3 SURGICAL BURN WOUND TREATMENT

9.3.1 Escharotomy

Full-thickness circumferential and near-circumferential skin burns result in the formation of a tough, inelastic mass of burnt tissue (eschar). The eschar, by virtue of this inelasticity, results in the burn-induced compartment syndrome. This is caused by the accumulation of extracellular and extravascular fluid within confined anatomic spaces of the extremities or digits. The excessive fluid causes the intra-compartmental pressures to increase, resulting in collapse of the contained vascular and lymphatic structures and, hence, loss of tissue viability. The capillary closure pressure of 30 mm Hg, also measured as the compartment pressure, is accepted as that which requires intervention to prevent tissue death.

Escharotomy is the surgical division of the nonviable eschar, which allows the cutaneous envelope to become more compliant. Hence, the underlying tissues have an increased available volume to expand into, preventing further tissue injury or functional compromise.

Escharotomy is considered an emergent procedure in burn treatment protocols. However, it rarely needs to be performed in the emergency department at the time of initial presentation of the severely burned patient. Advanced ventilation methods allow the patient to be stabilized to allow for expeditious transfer to the intensive care unit or the surgical suite, where the procedure can be performed under more controlled circumstances.

9.3.2 Negative pressure wound therapy

Negative pressure wound therapy (NPWT) is a relatively new, non-pharmacological, wound management modality. The vacuum-assisted closure device, introduced by Argenta and Morykwas, has been used widely in many surgical services ever since. The result is a well-perfused, ready-for-graft take, granulation tissue. The NPWT has been used for a broad indication spectrum ranging from eradication of infection. Its action mechanism is believed to be stimulation of mitogenesis and elaboration of growth factors, due to imposed tissue strain, evacuation of excessive tissue fluid or oedema, and reduction of bacterial colonization within the wound. The NPWT has been used for a broad indication spectrum ranging from eradication of infection and decrease of the depth in cavity wounds to stimulation of granulation tissue in areas with exposed tendon or bone, in order to choose a simpler reconstruction option at a later date. Advances in the actual device include smaller size, allowing for portable units for home use, increased ability to remove large amounts of fluid, in the wound for continuous irrigation, refinements in the foam with more consistent pore sizes, different sponge materials including silver, and increased safety and alarm systems.

Acute wounds are now more frequently being treated with NPWD closure. In patients with significant comorbidities or other serious injuries, NPWDs can be used in large soft-tissue injuries, contaminated wounds, and wounds with compromised tissue. The protocol is altered to include more frequent dressing changes with serial debridement as necessary. There are several descriptions of the sponge being placed over vital structures such as vessels, nerves, viscera, or even heart or lung. Ideally, muscle or soft tissue should be placed between the structure and the sponge, but if this is not possible Vaseline or silicone mesh should be used. This allows simplified wound closure in critical patients allowing the focus to shift to stabilizing the patient for later definitive reconstruction with flaps³⁴.

9.3.3 Stem cell therapy

The ultimate goal of the treatment of cutaneous burns and wounds is to restore the damaged skin both structurally and functionally to its original state. Recent research advances have shown the great potential of stem cells in improving the rate and quality of wound healing and regenerating the skin and its appendages. Stem cell-based therapeutic strategies offer new prospects in the medical technology for burns and wounds care. Stem cells that have been or might be used for burns and wound management; the potential role of stem cells in skin tissue engineering; the wound healing modulation capacity of stem cells especially bone marrow-derived mesenchymal stem cells in treating chronic and non- healing wounds³⁵.

9.3.3.1 The Involvement of Stem Cells in the Wound Healing Process

It is well-known that during the inflammatory phase of wound healing, blood-borne immuno-competent cells invade the wound area; recent evidence suggests that bone marrow-derived stem cells are also recruited into the wound site. This is not completely surprising, since a small number of hematopoeitic and mesenchymal stem cells is always present in peripheral blood. Furthermore, severe injury has been shown to increase the number of circulating stem cells^36,37.

9.3.3.2 Adult stem cells from bone marrow

The development of therapies using stem cells in the context on injury and wound healing has primarily relied on adult stem cells, and especially mesenchymal stromal cells, also known as mesenchymal stem cells (MSCs). MSCs are self-renewing and capable of differentiating into various tissues and cells, including skin cells. MSCs can be isolated from the patient‘s bone marrow and other tissues such as adipose tissue, nerve tissue, umbilical cord blood, and dermis^38,39. The other important benefit of MSCs is that even allogeneic MSCs induce little immunoreactivity in the host after local transplantation or systemic administration. Hence, MSCs have received considerable attention for modulating wound repair. MSCs have been examined in skin repair and regeneration after various acute and chronic skin injuries, such as acute incisional and excisional wounds, diabetic skin ulcers, radiation burns, and thermal burns. Bone marrow-derived MSCs appear to synthesize higher amounts of collagen and several growth and angiogenic factors, when compared to native dermal fibroblasts, indicating a potential use in accelerating wound healing^40,41,42.

9.3.4 Skin Grafting with Autografts

Wounds that extend deep into the dermis tend to heal very poorly and slowly because no keratinocytes remain to reform the epithelium. For such wounds, skin grafting with an autograft is the treatment of choice; since the patient donates its own tissue, there is no risk of rejection. A dermatome, which is a surgical instrument that holds a razor-sharp blade parallel to the skin surface, is used to remove a thin layer of skin from the donor site (most commonly a conspicuous area such as inner thighs and buttocks) that includes the full epidermis and portion of the dermis, or what is commonly known a split-thickness graft. The skin graft is then placed on the wound site. If large areas need to be covered, such as in cases of extensive burns, the graft is meshed to enable stretching it over the larger area. The appearance of the healed wound is best if the graft is thicker (thus including more dermis) and unmeshed, and those factors are taken into consideration depending on the site of grafting⁴³. Conversely, healing of the donor site will be more compromised if a thicker graft is harvested. In general, the thicker the underlying dermis, the better the graft take, the faster the healing, and the better the long-term appearance of the healed wound. Donor sites will heal and can be reharvested, albeit a limited number of times because the dermis does not regenerate and becomes thinner each time⁴⁴.

9.3.5 Skin Allografts and Xenografts

Skin grafting with an autograft may not be immediately possible because of limited availability of donor tissue. In this instance, wounds may be covered with allografts, which will serve as temporary covering since they typically get rejected by the host‘s immune system after a week. Allografts are harvested from consenting donors after death and stored frozen in skin banks where they can be used whenever needed. Allografts provide a barrier function and it is thought that growth factors released from these grafts have a positive effect on wound healing until an autograft can be placed onto the wound. Xenografts made of pig skin have also been used for the same purpose⁴⁵.

9.3.6 Uncultured skin autograft

9.3.6.1 Sheet Graft

Sheet Graft is piece of donor skin, removed from a un-burned area of the body, a process called ‘harvesting the donor’. The size of the donor skin that is used to patch a burned area is about the same size as the burn size. The donor sheet is laid over the excised wound and stapled in place. The disadvantages of sheet grafts are that small areas of graft might be lost from build up of fluid (hematoma) under the sheet right after surgery. Sheet grafts also need a larger donor site than meshed skin. A sheet graft is usually more durability and scars less⁴⁶.

9.3.6.2 Meshed skin graft

It is difficult to cover when there is very large areas of open wounds because of not enough unburned donor skin availability. So, it is necessary to enlarge donor skin to cover a larger body surface area. Meshing is a mean to enlarge donor skin. Meshing involves running the donor skin through a machine that makes small slits, which allows expansion similar to that in fish netting. In a meshed skin graft, the skin from the donor site is stretched to allow it to cover an area larger than itself. Most donor skin is meshed at a 1:1 or 1:2 ratio because the larger the size mesh the more fragile the graft. The disadvantages of meshing are to be a less durable graft than a sheet graft. Meshing serves two purposes: it allows blood and body fluids to drain from under the skin grafts, preventing graft loss, and it allows the donor skin to cover a greater burned area because it is expanded⁴⁷.

9.3.6.3 Cultured skin autograft

In massive burns, however, the available skin donor sites for autografting may be very limited. This has fostered the development of alternative methods such as autologous cultured skin graft and allograft skin substitutes as mentioned before. Two main techniques in autogenous graft for burn treatment include "cultured epithelial autografts; CEA" and "cell suspension".

9.3.6.4 Cell cultured epithelial autograft (CEA)

Cultured sheets of human autologous epithelium (CEA = cultured epithelial autografts) still represent the "gold standard" to resurface large wounds. So, cultured epidermal sheet autografts became available to complement autologous split thickness skin grafts in treating major burns or other large wounds. First harvesting the cell sheets from the culture dishes by trypsin treatment could damage the anchoring proteins of the cells. This could be one of the reasons of a mechanical instability of epidermal sheet grafts and insufficient dermal–epidermal reconstitution that lowers the uptake ratio of the grafts for a long time after transplantation. Second, epidermal sheet grafts usually require a long fabrication period. Third, cultured epidermal sheet grafts composed of fully differentiated keratinocytes might not exhibit further proliferation of keratinocytes after transplantation. Fourth, epidermal sheets are only 8–10 cells thick, which make them fragile and difficult to handle and have high costs of production. These shortcomings have led to a progressive development of skin culture techniques and an increased use of suspensions of keratinocytes single cells being transplanted instead of sheet grafts⁴⁸.

9.3.7 Cell suspensions

Surprisingly good clinical results using the technique of "epithelial cell seeding" had been published by von Mangoldt as early as in 1895 to treat chronic wounds and wound cavities. In his original description he harvested epithelial cells or cell clusters by scrap- ing off superficial epithelium from a patient´s forearm with a surgical blade until fibrin was exudated from the wound. This mixture was then applied to wounds. He claimed reduced donor site morbidity and a more regular aspect of the resurfaced wounds when compared to the method of Reverdin, which was the common method at that time. One of his key observations was the fact that single cells or cell clusters would better attach to the wound bed than conventional pieces of skin novel technique in which they used an aerosol device to spray epithelial cells on wounds in pigs. They noted that re-epithelialisation, re-growth of epithelial tissue over a denuded surface, was quicker than in unsprayed controls. Further advantages of suspension transplantation are to reduce time needed for culture and the fact that suspended keratinocytes can be transported from laboratory to patient in small vials, thus reducing the costs involved and storing frozen in clinic for transplantation. Because the cells, in culturing and transplanting, are as a suspension rather than a sheet; the use of enzymes like, Dispase1 can be avoided. Later this technique was further by combining it with meshed split thickness skin grafts and faster healing and a better quality of cells were reorted when they were sprayed.

9.3.8 Skin tissue engineering

The skin is indeed a complex structure incorporating a fusion of several different cell types, integrated within a three dimensional matrix containing both fibrillar and non-fibrillar elements. To synthesize such a complex structure by identifying the component parts and to put them together is neither practical nor realistic. It must be observed, however, that this integrative strategy has been the major one used in skin tissue engineering during its less productive phase. Three factors should be considered in the development of tissue-engineered materials: the safety of the patient, clinical efficacy and convenience of use. Any cultured cell material carries the risk of transmitting viral or bacterial infection, and some support materials (such as bovine collagen and murine feeder cells) may also have a disease risk. There must be clear evidence that tissue-engineered materials provide benefit to the patient. Essential characteristics are that it heals well and has the physical properties of normal skin. To achieve effective healing, the tissue- engineered products must attach well to the wound bed, be supported by new vasculature, not be rejected by the immune system and be capable of self repair throughout a patient’s life. Finally, materials need to be convenient to use or they will not achieve clinical uptake. Most tissue-engineered skin is created by expanding skin cells in the laboratory and used to restore barrier function or to initiate wound healing. There are those that replace the epidermal layer only, those that provide a dermal substitute, and a small number that provide both. In some clinical conditions (such as non-healing ulcers and superficial burns) simply transferring laboratory expanded cells can benefit patients, but the treatment of major full-thickness burns requires the replacement of both dermis and epidermis. There are four major challenges in this field: improving safety, finding a substitute for split-thickness grafts, improving angiogenesis in replacement tissue once it has been grafted to the wound bed, and improving ease of use. Although progress has been made in developing new treatments for burn victims, including skin grafting and artificial skin technologies; these cultured skin grafts do not have hair follicles, sweat glands and other features of normal skin. The result is thin, inflexible skin (which hampers mobility of joints), and skin that dramatically differs from the remaining healthy skin. A promising alternative to these techniques is stem cell-based therapy⁴⁹.

9.3.9 Hyperbaric Oxygen Therapy

Hyperbaric oxygen therapy (HBOT) is the use of 100% oxygen at pressures greater than atmospheric pressure. Today several approved applications and indications exist for HBOT. HBOT has been successfully used as adjunctive therapy for wound healing. HBOT is also indicated for infected wounds like clostridial-myonecrosis, necrotising soft tissue infections, Fournier's gangrene, as also for traumatic wounds, crush injury, compartment syndrome, compromised skin grafts and flaps and thermal burns. Another major area of application of HBOT is radiation-induced wounds, specifically osteo-radionecrosis of mandible, radiation cystitis and radiation proctitis. HBOT should be considered in these situations as an essential part of the overall management strategy for the treating surgeon.

The mechanism of action of hyperbaric oxygen is not clearly understood. Initial theories focused on increases in oxygen availability at the tissue level. The increased atmospheric pressure increases arterial oxygen pressure (PaO2), which in turn causes vasoconstriction. This vasoconstriction on the arterial end reduces capillary pressure, which promotes fluid absorption into the venous system thereby reducing oedema, as well as causing an increase in hyper-oxygenated plasma to the tissues. This effect typically lasts for several hours after the treatment has finished. Tissue repair processes such as collagen elongation and deposition and bacterial killing by macrophages are dependent upon oxygen, so increased levels, especially in wound areas that already have impaired perfusion, serve to facilitate wound healing⁵⁰.

9.3.10 Growth Factors and Biologic Wound Products

Biologic wound products have been an area of tremendous growth as our understanding of the details of the wound healing response has increased. In normal wound healing there is an orderly, predictable sequence passing through the inflammatory, proliferation, and remodeling/ maturation phases. This process is driven by numerous cellular mediators including eicosanoids, cytokines, nitric oxide, and various growth factors. The field of biologic wound products aims to accelerate healing by augmenting or modulating these inflammatory mediators. Eicosanoids are arachadonic acid metabolites including prostaglandins, prostacyclins, thromboxane, and leukotriene. They primarily affect the early stages of wound healing including initial vasoconstriction and later vasodilation, vascular permeability, and inflammatory cell chemotaxis and adhesion. The most well-known is prostaglandin E1 which inhibits platelet and neutrophil activation, reduces blood viscosity, stimulates tissue plasminogen activator production, and causes vasodilation by relaxing vascular smooth muscle. Cytokines regulate inflammation by influencing hematopoietic cells and include chemokine, lymphokines, monokines, interleukins, colony-stimulating factors, and interferons. Interleukin-1, stimulates most cells in the wound environment. Granulocyte/macrophage colony-stimulating factor (GM-CSF) has been most extensively studied. Its effects are to stimulate neutrophils, macrophages, keratinocytes, and fibroblasts and increase VEGF production, rendering it a very promising molecule in wound healing. Growth factors stimulate mainly fibroblasts and keratinocytes via trans-membrane glycoproteins. They are divided into five super-families, the most known being the platelet-derived growth factors. The rhPDGF group showed a statistically significant higher percentage of patients that achieved wound healing, 48% versus 25%, as well as a greater reduction in wound size (Table 6). It is the only current FDA-approved product in the growth factor family⁵¹.

10. CONCLUSION:

Wounds are one of the most harmful and complex physical injuries. They often happen unexpectedly and have the potential to cause death, lifelong disfigurement and dysfunction. The challenge of surviving a major woundable depends on skin repair. In recent years, the field of wound management has shown rapid advances. This review focuses on treatment and new advancements that have been used in recent years for the proper healing of the wounds. The effective management of wounds will reduce the number of complications and allow rapid return to normal function. The wound should be protected with dressings that are chosen according to the stage of healing. Recently, skin grafting has evolved from the initial auto-graft and allograft preparations to biosynthetic and tissue-engineered living skin replacements. Tissue engineering now provides the clinician with more therapeutic options and more challenges. Consequently, it is essential to critically analyze the clinical needs of skin repair and understand skin replacement in terms of the availability, compatibility, safety and durability.

11. ACKNOWLEDGEMENT:

The authors are thankful to Director, University Institute of Pharmacy, Pt. Ravishankar Shukla University, Raipur (C.G.) for providing necessary facilities relating to present work and UGC-MRP 41-748/2012 (SR); CGCOST (CCOST/650/2011); UGC-RAF- 30-5/2011 (SA-II) for financial assistance for the studies.

Names	Layers involved	Appearance	Texture	Sensation	Time to healing
Superficial (First degree)	Epidermis	Redness	Dry	Painful	2-3 days
Superficial partial thickness (Second degree)	Extends into superficial (papillary) dermis	Red with clear blister. Blanches with pressure	Moist	Painful	1-2 weeks
Deep partial thickness (Second degree)	Extends into deep (reticular) dermis	Red-and-white with bloody blisters. Less blanching.	Moist	Painful	3-4 weeks
Full thickness (Third degree)	Extends through entire dermis	Stiff and white/brown	Dry, leathery	Painless	Prolonged and incomplete
Fourth degree	Extends through skin, subcutaneous tissue and into underlying muscle and bone	Black; charred with eschar	Dry	Painless	Requires excision

S.No.	Type of dressings	Uses
1.	Retention Dressing	Low profile dressings used to assist adherence of other dressings or as primary dressing for superficial (minimally exudating) wounds
2.	Hydrocolloids	Low profile, waterproof, highly conformable, wound interactive dressing
3.	Alginates	Haemostatic dressing for moderately exudating or bleeding/oozing wounds
4.	Foams	Used to control moderate to highly exudating wounds or protect fragile healed or almost healed area
5.	Hydrogels	Used to maintain or introduce moisture into a wound. May be used to protect and hydrate exposed tendons or bone.
6.	Absorbent dressing	Used to mop up heavily exudating wounds
7.	Non-stick dressing	Used as anti-shear layers in dressing systems
8.	Wound Growth Factor Impregnated Dressings	Low profile, interactive, dressings / films which are often used acutely to reduce / prevent wound progression
9.	Biological dressing	Preparations used to provide another option for introducing growth factors onto the wound e.g. xenograft.
10.	Films	Low profile, waterproof, highly conformable, adhesive dressing.

Growth factor	Abbreviation	Main origins	Effects
Epidermal growth factor	EGF	Activated macrophages Salivary glands Keratinocytes	Keratinocyte and fibroblast mitogen Granulation tissue formation
Transforming growth factor-α	TGF-α	Activated macrophages T-lymphocytes Keratinocytes	Hepatocyte and epithelial cell proliferation Expression of antimicrobial peptides
Hepatocyte growth factor	HGF	Mesenchymal cells	Epithelial and endothelial cell proliferation Hepatocyte motility
Vascular endothelial growth factor	VEGF	Mesenchymal cells	Vascular permeability Endothelial cell proliferation
Platelet derived growth factor	PDGF	Platelets Macrophages Endothelial cells Smooth muscle cells Keratinocytes	Granulocyte, macrophage, fibroblast and smooth muscle cell chemotaxis Fibroblast, endothelial cell and smooth muscle cell proliferation Angiogenesis,Wound remodelling
Fibroblast growth factor 1 and 2	FGF-1, −2	Macrophages Mast cells T-lymphocytes Endothelial cells Fibroblasts	Fibroblast and keratinocyte proliferation Keratinocyte migration Angiogenesis Wound contraction
Transforming growth factor-β	TGF-β	Platelets T-lymphocytes Macrophages Endothelial cells Keratinocytes Smooth muscle cells Fibroblasts	Granulocyte, macrophage, lymphocyte, fibroblast and smooth muscle cell chemotaxis Angiogenesis Fibroplasia Matrix metalloproteinase production inhibition Keratinocyte proliferation
Keratinocyte growth factor	KGF	Keratinocytes	Keratinocyte migration, proliferation and differentiation