Elia Ricci, Andrea Cavicchioli, and Marco Romanelli
Dressing a wound means applying local treatment, although it should be remem- bered that the medication of a wound in itself is only a part of the treatment and will generally help the healing process but not necessarily determine it. The objec- tives of medication have been established for some time now, especially in terms of microenvironment and bacterial level. There are two main theories of medica- tion: traditional and advanced, as illustrated in Table 13.1.
Choice of Dressing
One of the problems in the choice of dressing is the wide variety of products avail- able on the market. We have divided the dressing products into 12 groups, derived from a previous classification proposed by Ricci and Cassino,1with the intention of providing a general guide within the context of this vast choice.
The classification is as follows:
1. Gauzes: These may be simple dressings or may be impregnated with various substances (thus becoming primary medications in themselves and splitting up into various categories).
2. Antiseptics—antibiotics: The former are substances aimed at reducing the bacterial level and work by damaging the membrane or other cellular structures without inducing resistance. The most widely used are silver, iodine, chlorhexidine, and hypertonic solutions. They may take various forms such as solutions, creams, impregnated gauze dressings, granules, etc. Local antibiotics, long opposed by international literature, are now coming back into fashion with the discovery of products that induce a limited level of resistance and act locally (chlorampheni- col, bacitracin, neomycin, etc.).
3. Adsorbents: These are dressings aimed at removing the exudate excess from the wound bed and take the form of granules, gel, ionic membranes (which are selective with particular regard to bacteria), alginates, and surgical fibers (which work by means of a gelling process). The latter two types of dressing have some of the typical characteristics of advanced products, but are not insulators or thermally stable. They therefore represent a link between the two categories of tra- ditional and advanced dressings. Recently they have been used as mediums for active ingredients (e.g. silver as an antiseptic).
4. Proteolytic enzymes: These are enzymes aimed at breaking down necrotic tissue. They may be derived from bacteria (collagenase), vegetables (papain), or
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animals (krill). They are used mainly for cleansing and, given their nature, are deactivated by drying or antiseptics. The stipulated application times should be respected.
5. Products encouraging granulation: The action of these products, despite much debate, is not yet fully understood. They are made from collagen or hyaluronic acid and their effect, depending on the formulation, is to provide a frame for vascular development (tablets), to control inflammation (spray, gauze), or to activate cleansing (creams).
6. Polyurethane films: These are very fine films of varying permeability, used to dress superficial wounds that are dry or with reduced exudate; alternatively they may be used as a secondary dressing. The permeability is rated according to the MVTR (moist vapor transmission rate), which indicates the transmission of vapor through the film. Conventionally an MVTR below 1000 indicates an occlusive dressing while above 1000 it indicates a semi-occlusive dressing.
7. Polyurethane foams: These are made from the same material as the film, but in a three-dimensional form, with micro cells that absorb the discharge while maintaining a moist microenvironment and controlling the excess liquid.
Suitable for cleansed wounds with medium discharge, they should be replaced when they become saturated (appearance of the liquid on the surface of the dressing) or start to leak. They are sometimes covered on the outer layer by an impermeable film and can then be used on flat wounds; without such outer covering they may be used as intracavitary dressings. They may be adhesive or non-adhesive.
8. Hydrocolloids: These are amorphous colloids in the form of wafer, paste, or granules. They are dressings with reduced permeability and are generally occlusive. They work through absorption of the discharge and transformation of it into a fluid gel. Suitable for cleansed wounds with low to medium discharge, they have a good fibrinolytic influence and cleansing effect in the case of limited necrosis.
9. Hydrogels: These can be divided into two forms—fluid and on a base. Fluid hydrogels are used to induce the hydrolysis of necrotic tissue and should be used with a secondary dressing of an advanced type. Hydrogels on patches are occlusive dressings with a low-to-medium absorbency and are suitable for use in encouraging the re-epithelialization of cleansed wounds or wounds with slough.
Table 13.1. Dressing philosophy
Traditional dressing Antisepsis
Hemostasis Drying the wound Covering the wound
Advanced dressing Moist environment
Thermal stability
Isolation from foreign environment Control of exudate
Removal of necrosis and nonviable tissue Low cost
Infection prevention
10. Interactive dressings: These include the group of biodressings, skin deriva- tives, metalloprotease inhibitors, engineered tissue, and growth factors. These tech- niques are for use by specialists only and their use is described in the section on interactive dressings below.
11. Technical devices: These are an evolution of dressing/debridement tech- niques, which combine machine-controlled functions with the action of the dressing. Although only used to a limited extent as yet, they are acquiring greater importance in daily practice. The most widespread product at the moment is the VAC system described in the section on topical negative pressure therapy below.
12. Non-allopathic dressings: A wide range of products held to be effective in the treatment of cutaneous lesions, often without clinical studies to support them.
Although frequently based on traditions and customs that are centuries old (e.g.
aloe, honey), their usage should be postponed until the effects have been scientifically proven.
With regard to guidelines for use, in a text aiming to provide quick consultation we will limit ourselves to giving some general indications. Dressing a wound means choosing the right product for the wound at its specific stage and deciding on the length of application.2 Generally speaking we can say that the clinical status of the wound and the tissues present determine the choice of product to be used: the quantity of exudate will determine the wear time of the dressing in inverse pro- portion.3Table 13.2 shows the various clinical stages of wounds and the products suitable for dressing them.
Interactive Dressings
The next frontier in the treatment of cutaneous lesions is represented by dressings and products created by means of engineering tissues; these enable those operat- ing in the sector to intervene directly in the healing process (Figures 13.1 and 13.2—see color section). We may say that traditional medication, based mainly on
Table 13.2. Dressings and guidelines for their use, based on clinical examination of the wound
Wound Dressing
Colonized/infected Antiseptics
Local antibiotics Ionic adsorbents Hypertonic dressings
Necrotic Lytic enzymes
Hydrogel
Sloughy Lytic enzymes
Hydrogel Hydrocolloids Hypertonic dressings
Cleansed Products encouraging granulation
Polyurethane film and foam Hydrocolloids
Adsorbents
antisepsis, has turned its attention towards the outside environment and its inter- action with the wound. Advanced dressings attempt to create an environment that encourages spontaneous repair.4 With the progressive gains in scientific knowl- edge, determined in part by increased attention to the problem, and expressed and organized according to the theories of wound bed preparation (WBP) and con- centrating in particular on the identification of corrupt and functionally limited cellular matrices in chronic cutaneous lesions, the need to interact with the healing process directly has become pressing.
We may begin by dividing these products according to method, drafting a classification as shown in Table 13.3.
This is a field that needs further exploration; not all the mechanisms behind the effects have been fully understood and the timing of their use needs to be defined; however, the initial results are promising (Figures 13.3 and 13.4—
see color section). The use of single growth factors needs developing, espe- cially considering the specific language involved, which is still far from being understood.
The basic objective (which also requires developing) and the hope for this approach to dressing is to change the wound bed from a chronic to an acute state.
Therapeutic Devices
Pressure ulcers represent a major health problem, causing a considerable amount of suffering for patients and a high financial burden for healthcare systems. The percentage of the population that is geriatric, and therefore with an increased risk of chronic wound development, is rising constantly. Evidence clearly indicates that preventive measures are essential to reduce the prevalence rates of pressure ulcers;
therefore healthcare professionals must be able to identify the appropriate strate- gies to adopt, in order to meet the individual patient’s requirements.
The past decade has seen a rise in the number of therapeutic options available for the management of acute and chronic wounds. The introduction of advanced medical devices and new concepts of systemic treatment have led to a better under- standing of the mechanism of tissue repair in chronic wounds, which has been supported by the development of standardized guidelines for prevention and treatment.
Topical Negative Pressure Therapy
Wound management with negative pressure represents a non-invasive mechanical wound care treatment, using negative pressure to facilitate wound healing.5VAC®
(Vacuum Assisted Closure) therapy is used to reduce wound fluid, stimulate granulation tissue formation, and reduce bacterial colonization. Negative pressure wound therapy acts by localized and controlled negative pressure, which is applied in continuous or intermittent cycles.6,7The equal distribution of negative pressure to every surface of the wound is ensured by a polyurethane open-cell foam dress- ing. The foam is trimmed to fit the entire surface of the lesion, placed in the wound bed, and sealed with an adhesive drape (Figure 13.5—see color section).
Negative pressure is applied via an evacuation tube by means of a computerized,
Table 13.3. Interactive dressings
Group Action Name
Surgical
Surgical procedures Removal of degraded cells from the wound bed.This is an invasive, painful technique Debridement and is expensive.
Wet to dry Progressive removal of the bottom layer of the wound by tearing, using gauzes made Wet to dry to stick to the wound bed. Extremely painful.
Grafting Removal of the wound bed until healthy tissue is reached, after which the wound is Grafting covered with skin taken from elsewhere on the patient. If the skin takes,
immediate healing is achieved; if not, there may in any event be a rapid resumption of the repair process and re-epithelialization.
Skin substitutes
Glycerol skin This is skin taken from organ donors and treated with glycerol, which makes it Skin bank non-vital and suitable for preserving. It was originally intended for use as a
biological covering for patients with severe burns and has been progressively extended to chronic wounds. It is not clear how it works and a thoroughly cleansed base is required.
Cryopreserved skin Skin taken from organ donors and preserved by freezing. Used as a biological covering, Skin bank it may work by releasing growth factors.
Culture-grown skin After a skin biopsy, the cells are placed on special mediums which make them larger Apligraf®
and more concentrated.This is an autograft, which is capable of activating the repair process.
Heterologous culture- Skin substitute derived from the fetal prepuce.This is a heterologous graft that is Dermagraft®
grown skin capable of reactivating repair processes (growth factors?) and of taking in some cases that are not clearly defined as yet.
Metalloprotease inhibitors
Metalloprotease Metalloprotease, elastase and plasmin are enzymes derived from cellular decay, Promogran®
inhibitors which are capable of halting the healing process when present in large quantities.
These products, made from oxidized and regenerated cellulose, appear to be able to deactivate the excess of such enzymes and to bind them.
Growth factors
Growth factor Proteins capable of mediating cellular functions through membrane receptors.
Produced by a secretory mechanism within the body itself, they are currently being studied and are produced industrially by means of recombinant genes.The principal ones involved in the healing process are: platelet-derived growth factor (PDGF), transforming growth factor beta (TGFb),TGFa,tumor necrosis factor (TNF), insulin-like growth factor (IGF), interleukin enhancer binding factor (ILF), interleukin-1 (IL-1), IL-2, nerve growth factor (NGF), vascular endothelial growth factor (VEGF), beta fibroblast growth factor (FGF), keratocyte growth factor (KGF).
Platelet gel Prepared on the spot from the patient’s or donor’s serum (from a blood bank) or Regranex®
prepared industrially, these act by releasing large quantities of growth factors, mainly PDGF.
Cultured cell
Culture-grown Once a sample of skin has been taken, the fibroblasts are isolated and grown so as to Hyalograft 3D®
fibroblasts create a sort of “three-dimensional dressing” on a hyaluronic acid base.This is a self-graft of fibroblasts, the cells responsible for healing processes and growth factors.
Culture-grown As with the fibroblasts, a sample of skin is taken and once the keratinocytes have Laser Skin®
keratinocyte been isolated they are cultivated on a transparent sheet of hyaluronic acid. Hyalograft 3D KC®
This is a very delicate product and its established use for treating acute wounds has yet to be discussed for chronic wounds.
Other
Engineered derma Three-dimensional structure made from cellulose and collagen or hyaluronic acid Integra®
capable of providing a base mainly for neovascularization, which is considerably Hyalomatrix®
increased. It is covered with a coating which must be removed after 1–3 weeks.
programmable pump. The target pressure for wound therapies varies from 50 mmHg to 200 mmHg, based on the characteristics of the individual wound. In pressure ulcers, a negative pressure of 125 mmHg is used in a continuous cycle of 48 hours. Negative pressure therapy provides a moist wound healing environment, assists in uniformly drawing the wound border, enhances epithelial migration, reduces bacterial colonization, and reduces localized edema by increasing local blood perfusion and accelerating the rate of granulation tissue formation.8
Despite the successful treatment of different wound types, some limitations may occur when attempting to treat certain areas of the body that involve irregular sur- faces surrounding the wounds, such as the perineum.9VAC® therapy is indicated in acute and traumatic wounds, dehisced incisions, neuropathic ulcers, stage 3 and 4 pressure ulcers, vascular wounds, and chronic debilitating wounds. Split- thickness mesh skin grafts also benefit from VAC® therapy.
Contraindications for negative pressure treatment include cutaneous malignant lesions, untreated osteomyelitis, necrotic tissue within the wound bed and fistula directly communicating with organs and cavities. Caution should be used when there is active bleeding, unstable local hemostasis, use of anticoagulants, or distal diabetic foot lesions.10The nutritional status of the patient should be stable and the patient should be continuously monitored by nurses and should be positioned on a support surface so as to redistribute his or her weight over a large area and reduce pressure. An adequate amount of intact peri-wound skin for adherent dressing should be available and the ulcer should be free of necrotic tissue or osteomyelitis.
The dressing is changed every 48 h or every 12 h if infection is present. The wound bed is cleansed per routine, the sponge is placed in the wound, and the evacuating tube is laid on top of the foam, linked to a collection chamber located on the pump. An adhesive clear dressing is placed over the foam and the tube.
Duration of the therapy varies from 4 to 6 weeks, with continuous or intermittent cycles of treatment.11Continuous therapy facilitates removal of wound fluids and reduction of edema, while intermittent therapy acts as a mechanical stretch and results in the repeated release of biochemical messengers. Wound measurement, tissue and fluid characterization, odor, and surrounding skin should be monitored at each dressing change.
Negative pressure therapy should be used in pressure ulcers to achieve complete healing or to prepare the wound bed for surgical closure, especially in chronic non- healing wounds of considerable depth, rather than the traditional saline wet-to- moist dressings.
Hydrotherapy
Hydrotherapy is another treatment that is frequently used in many countries, prin- cipally in patients with leg ulcers.12The patient is immersed in special pools where the water, containing antiseptics, is shaken with artificial movement so as to make the removal of dead tissue easier. Hydrotherapy provides cleansing pressure- irrigation and hydromassage. The cleansing is useful either to remove secretions and bacteria or to soften necrotic wound material. This procedure is generally per- formed with a saline solution only or with an antiseptic solution or with other types of detergent solutions—used according to wound conditions and dressing compatibility. Pressure-irrigation uses water pressure to remove the necrotic mate-
rial from the wound surface.13However, if the pressure used to deliver irrigation solution is too low (below 4 psi), the lavage will not clean effectively; therefore, pressure irrigation has to be in a range from 4 to 15 psi.
A simpler method uses a 35 ml syringe with a 19-gauge needle producing an 8 psi pressure action, which is able to clean a wound without causing damage to new granulation tissue.
Another method makes use of hydromassage, that is, water pressure jets gener- ated in a whirlpool. In this case the tissue becomes soft in the whirlpool and is removed by the pressure of the jets. The massage reduces edema and inflamma- tion and improves circulation in ischemic legs. A further refinement of this tech- nique consists of immersing the patient for 20–30 minutes after a 30-second treatment at maximum pressure. The sessions are twice-weekly. This method is indicated in very exudative wounds, necrotic wounds, and eschars, but is con- traindicated in clean and granulation wounds.
Moreover, there are now special devices available that can direct a high-pressure water jet onto lesions and then, with suction, remove the devitalized tissue before it dissolves. Among such instruments, one that deserves particular attention is a device developed in Switzerland, based on high-pressure microjet technology. The device consists of a liquid pump driven by compressed air, which generates high hydraulic pressure in a liquid directed through a nozzle installed in a hand-piece.
The major advantage of this debridement technique is the reduction of the dura- tion of treatment. The aim is to provoke a decisive healing impulse in a stagnant wound. Through the nozzle, Ringer solution, NaCl or aqua ad injectabilia are injected onto the surface of the wound in the form of a very fine jet under pre- cisely controlled pressure. The duration of each intervention depends on the importance and degree of necrosis of the wound and varies from 10 to 30 minutes, usually at weekly intervals. Advanced dressings sustain the treatment. The three major results of this application are: shortening of the wound healing process, reduction of the scar tissue, and low stress effects for the patients, because the treat- ment is relatively painless. These treatments are contraindicated in patients suf- fering from anticoagulation, tumors, and unprotected or open blood vessels.
Warming Therapy
Most chronic wounds become hypothermic and hypothermia has been shown to impair the healing process by reducing the normal function of the immune system and promoting wound infection. A recent technology utilizing radiant heat was introduced for the treatment of chronic wounds. This warming treatment is able to maintain 100% relative humidity at the interface between dressing and wound bed and to restore both peri-wound and wound bed temperature toward nor- mothermia. The system is provided with a temperature control unit (TCU), which operates either from an AC outlet or with a rechargeable battery pack for porta- bility. A disposable wound cover made of a polyurethane foam provides a non- contact surface that will not disrupt the wound, will absorb the exudate, and has a transparent window which provides easy viewing for monitoring wound progress. An infrared warming card, which is connected to the TCU, slides into a sleeve in the cover and warms to a temperature of 38°C. Using warming therapy, the skin and subcutaneous tissue are returned to a temperature that is closer to normal. Warming encourages blood vessels to dilate, which increases blood flow
to the wound and peri-wound area. Greater blood flow delivers more oxygen, nutri- ents, and growth factor to the wound. The use of warmth on fibroblasts and endothelial cells in vitro was found to reduce the inhibitory effect of chronic wound fluid upon neonatal fibroblasts.14In a recent study the warming therapy was compared to standard treatment in patients with stage 3 to 4 pressure ulcers.15 Results showed a statistically significant accelerated rate of healing for patients receiving heat therapy compared to standard treatment.
References
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