Dressing in Wound Management

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Dressings in Wound Management

Sarah M.E. CockbillUniversity of Wales Cardiff, Cardiff, U.K.

INTRODUCTION

Throughout history, diverse materials of animal,vegetable, and mineral origin ranging from hot oilsand waxes reported in the Ebers papyru[1] throughanimal membranes and faeces of the Middle Ages tothe picked oakum of the 19th century; have been usedto treat wounds. Moist poultices are described onSumerian tablets inscribed as early as 2100 B.C.

[1,2]

Mediaeval manuscripts illustrate examples of both‘‘moist’’ environment and biological ‘‘healing’’ withthe practice of using dogs to lick wounds, particularlypostsurgery, to moisten, cleanse, and stimulate healingthus relying on the now recognized, but at that timeunknown, presence of antibacterial agents and growthfactors in the saliva.[3] Ambroise Pare (1510–1590),the ‘‘father’’ of wound management, used a semiocclu-sive, oil impregnated dressing in the 16th Centuryto obtain ‘‘a softness of the tissues.’’[4] A Diachylonplaster consisting of a mucilaginous, moist mass madefrom linseed and marshmallow was originallydescribed by Galen (130–201). In 1819, AbrahamRees, in his treatise on the use of lynette, emphasizedthe need to prevent ‘‘scab’’ formation by keeping thewound edges apart with oil soaked dossils.[5] Inthe 19th Century, wet compresses or cataplasma kao-lini were applied to wounds and covered in waterprooffabrics such as jaconet, batiste, or oiled silk to main-tain humidity. The 20th century saw the productionof leno gauze impregnated with soft paraffin,Tulle Gras.

The first authoritative monographs related towound dressing materials appeared in early Londonand Edinburgh hospital dispensatories and later inthe British Pharmaceutical Codices. The developmentof wound management products can be traced byexamining these Codices together with the BritishPharmacopoeia.[6] The information is reflected in simi-lar publications in the United States Pharmacopoeiaand other national standards.

Advances in the design and efficacy of wound man-agement products was spasmodic and limited to theadaptation of available materials until 1960. Up to thatdate, the products were primarily of the ‘‘plug and con-ceal’’ variety exemplified by lint, gauze, cotton wool,

and tow that were considered to be passive productswhich took no part in the healing process.

The new generation of products was a rejection ofthe traditional passive ‘‘cover all’’ dressing philosophyand was potentiated by advances in knowledge ofthe humoral and cellular factors associated with thehealing process and the realization that a controlledmicroenvironment is necessary if wound healing is toprogress at the optimum level, such environmentalcontrol dressings could be classified as interactive.

It is recognized that both the acellular and cellularactivities involved in the healing cascade are optimizedby a wound microenvironment that allows the freemovement of cells and effective response to bioactivecompounds. This optimal response can be expectedwhere environmental factors such as temperature andhumidity are at subdermal levels.

PERFORMANCE CRITERIA

The concept of moist wound healing is generally attrib-uted to George Winter after his much cited 1962 pub-lication in Nature,[7] although Bull, Squire, and Topheyin 1948[8] published results showing enhancement ofhealing under a ‘‘film’’ dressing.

Turner in 1979[9,10] identified the performance cri-teria for a wound dressing product that would success-fully contribute to an acceptable microenvironment.These were to:

� Maintain a high humidity at wound/dressing interface� Remove excess exudate and toxic components� Allow gaseous exchange� Provide thermal insulation� Afford protection from secondary infection� Be free from particulate or toxic contaminants� Allow removal without trauma at dressing change

These criteria are still valid. An additional require-ment with the advance in our knowledge of the growthfactors involved in the healing process is:

� To be compatible with the humoral and cellularfactors involved in healing.

Encyclopedia of Pharmaceutical Technology DOI: 10.1081/E-EPT-120041182Copyright # 2007 by Informa Healthcare USA, Inc. All rights reserved. 1023

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Humidity Levels and Removal of Exudate

Partial or full thickness wounds exposed to the airwill demonstrate a lower temperature than ambientdue to the latent heat lost through tissue fluid evap-oration. The clotting process and fibril developmentproduces an occlusive dry eschar or scab whicheffectively seals and insulates the wound thereby lim-iting moisture and gaseous transmission and restrict-ing the migration of epithelial cells to the moistsubscab tissue. The result is slow healing with a highcontamination and infection risk together with pos-sible excessive scarring in an excised wound fromclosure without full cavity granulation. The mainte-nance of a high humidity between the wound andthe dressing is therefore a requirement for rapid epi-dermal healing.

The absorption of excess exudate not only avoidstissue maceration but also removes exotoxins or celldebris that may retard growth or extend the inflamma-tory phase of the healing process. The balance betweenhumidity and absorption is critical and excessive wick-ing must be avoided to prevent drying and necrosis.

Gaseous Exchange

Gaseous permeability will allow water vapor trans-mission which may be particularly important in a highexudate wound such as a burn, sacral, or leg ulcer.Of equal significance will be the effect of gaseousexchange on oxygen (pO2) and hydrogen ion (pH)levels. Epithelization of the wound is greatly acceler-ated by the availability of atmospheric oxygen, whichdissolves in the serous exudate to supplement thatoxygen transported to the wound area by hemoglobinand subsequently directly utilized by the migratingepidermal cells.

Thermal Insulation

Thermal insulation will assist in maintaining thewound temperature at a level as close to body coretemperature as possible. Phagocytic and mitoticactivity are particularly susceptible to temperaturesbelow 28�C. Thermal insulation and ‘‘warm’’ dressingchange conditions are very important if the optimumhealing rate is to be maintained. Long exposure ofwet wounds may reduce the surface temperature tothe point where mitotic activity ceases. Recoveryof that tissue may take up to 3 hr. Temperatures of30�C and above may be found beneath a good insu-lating dressing, and this will result in high mitoticactivity with rapid epithelization and improvedgranulation.[11]

Impermeability to Micro-organisms

Bacterial impermeability has a dual role. The woundwill not heal if it is heavily infected. The inflammatoryphase will be extended, and, unless topical or systemicantibacterial agents are used, a more general infectioncould result. However, a limited number of micro-organisms are tolerated by most wounds, and thedestructive or cleansing phase produced by phagocyticactivity should result in a self-sterilized environment.The wound should be protected from secondary infec-tion or, if still contaminated, be prevented from trans-mitting the infective organisms.

A dressing should, therefore, be impermeable to air-borne micro-organisms, which may fall on its surfaceand penetrate to and infect the wound. It should alsoact as a barrier to any organisms that may be trans-mitted from the wound to the dressing surface andbecome airborne to thus cause cross-infection. Organ-ism transmission occurs most frequently in dressingsthat exhibit ‘‘strike through’’ of the exudate to thewound surface, providing a wet pathway to or fromthe wound surface. The passage of organisms can takeas little as 6 hr from the time of ‘‘strike through.’’

Freedom from Particulate and ToxicWound Contaminants

Both particles and toxic compounds that may contami-nate a wound will be responsible for disrupting thehealing pattern. The incorporation of fibrous particlesinto a wound may result in a granuloma that couldsubsequently reduce the wound strength and inducekeloid scarring. It is well documented that particulatecontamination can also reduce the infection resistancelevels by a factor of 1.0 � 10�6.

Trauma During Dressing Change

The wound environment may be optimally maintainedwith a product that has the preferred performanceparameters but, nevertheless, is disrupted during thedressing change. The hazards of temperature changeand secondary infection may be accompanied by a sec-ondary trauma caused by the dressing adhering to thewound and, on removal, stripping newly formed tissue.

This adhesion is normally caused by the adhesive-ness of the drying exudate and the trauma can beexaggerated on removal by the destruction of capillaryloops that have penetrated the dressing material(Fig. 1).

Although not associated with the production ofan acceptable microenvironment, there are certain

1024 Dressings in Wound Management

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physical characteristics required to assist in the overalldressing procedure. The dressing should have:[10]

� A size range to match the wounds� An absorption range for dry and heavy exudate

wounds� Good conformability and good handle when both

dry and wet� Sterility and be stable in storage� Be easily disposable

These parameters stimulated the development offunctional products using the advances that hadaccrued in the technology of materials. This develop-ment was closely followed by products derived fromthe advances in the development of synthetic polymers.A statement of required performance could now beconsidered a possible specification for a polymeric product.

The range of polymeric products manufactured assurgical dressings has included:

� Vapor permeable films� Polymeric foams� Particulate and fibrous polymers� Hydrogels and xerogels� Hydrocolloids

The above materials mark the progression towardsthe production of an ‘‘ideal wound dressing.’’ It should,however, be emphasized that no single dressing will pro-duce the optimum microenvironment for all wounds orfor all of the healing stages of one wound. The spectrumof performance requires that the wound is diagnosedand the treatment progressed by prescribing the mostsuitable dressing at each stage of the healing process.

This entry will now examine the range of dressingscurrently available, identify their principal chemicaland physical characteristics, and indicate their recom-mended clinical usage.

ABSORBENTS

The overall function of surgical absorbents is self-explanatory.[9,12] They are available in a number of forms:

� Fibrous (staple) absorbents� Fabric absorbents� Fiber plus fabric absorbents� Wound dressing pads

Fibrous Absorbents

These are made from cotton staple or from the fibers ofviscose or cellulose; viscose and cotton may be admixed.

Absorbent cotton

Absorbent cotton is available in different qualitiesvarying with the length and diameter of the cotton sta-ple. It is available in the form of rolls and balls and isused for cleansing and swabbing wounds, preoperativeskin preparation, and the application of topical medi-caments to the skin.

Absorbent viscose

The absorption performance and physical characterof absorbent viscose varies markedly with the

Fig. 1 Wound healing responseto a controlled microenviron-ment.

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manufacturing process. It is available in the brightor ‘‘dull’’ form, the latter containing a particulatematerial such as titanium dioxide within the fiber.The fibers are, in general, a continuous staple with acrenate trans-sectional profile but smooth and lami-nated forms are available which show different degreesof absorptive capacity and wet tensile strength.

Some fibrous absorbents contain a proportion ofacrylamide or other synthetic polymeric fiber. Theyfrequently enhance the absorptive performance andgive ‘‘body’’ to the fleece thus improving fluid reten-tion and avoiding ‘‘squeeze’’ out which is caused byfleece collapse after wetting.

Cellulose wadding

Cellulose wadding is produced from delignified woodpulp and manufactured in a multiple laminate materialform. It is used in large pieces to absorb large volumesof fluid in incontinence but is not used in contact witha wound unless enclosed in an outer fabric sleeve toprevent fiber loss to the wound.

Fabric Absorbents

Absorbent lint

Absorbent lint is a close weave cotton cloth with araised nap on one side that offers a large surface areafor evaporation when placed with the nap upwardson an exuding wound. Its use generally unacceptablein modern wound management.

Absorbent gauze

Absorbent gauze is the most widely used absorbentand consists of a cotton cloth of plain weave bleachedto a good white, clean and reasonably free from weav-ing defects, cotton leaf, and shell. It may be slightlyoff-white if sterilized. It absorbs water readily but itsperformance may be reduced by prolonged storage orexposure to heat.

Gauze products are primarily absorbents when usedpreoperatively, perioperatively, and postoperatively,but perioperatively, they are also required to performother functions, including the protection of tissue andorgans by occluding areas not involved in the pro-cedure, to assist the application of wet heat, whichmay establish the viability of doubtful tissue and toassist in blunt dissection where fascias are separatedalong the lines of cleavage, thus avoiding unnecessarycutting.[13]

The gauze fabric may contain a proportion of vis-cose incorporated with the cotton either in the warpand the weft or exclusively in the weft. A maximum

level of 45% viscose is widely accepted. A range ofgauze fabrics exist graded according to the numberof threads per 10 cm width of gauze.

Gauze products fall into two broad categories—the‘‘swab’’ or ‘‘sponge’’ type produced by folding andstitching the cloth and those consisting of plain cloth.The ‘‘swab’’ type includes swabs, strips, pads, andpledgets. The ‘‘plain’’ types include packs and ribbon.Gauze swabs or sponges are commercially available asgauze folded into rectangles or squares to give varioussizes or ply. They are folded in such a way that no cutedges are visible and the edges may be stitched. For usein an operating theatre, they are available with andwithout a radiopaque (X-ray detectable) mono- ormultifilament thread containing barium sulfate woveninto or heat bonded to the fabric. The commercialproduct can vary in size from 5 cm � 5 cm to10 cm � 15 cm with a variation in ply from 4 to 32.Some are colored with a suitable fast, non-toxic dye(Table 1).

Absorbent muslin

Absorbent muslin is a bleached cotton cloth of openweave used infrequently for the treatment of extensiveburns and as a wet dressing.

Non-Woven Fabrics

Non-woven fabrics include a wide range of productsmanufactured from synthetic and semisynthetic fibers.

Non-woven swabs

Non-woven swabs consist of a non-woven viscose fab-ric and are available in folded pieces of various dimen-sions. They have a lower total absorbent capacitythan gauze but absorb more quickly because of therandom orientation of the viscose fibers. As fabrics,they constitute the outer layer on a number of wound

Table 1 Absorbent gauze

Threads per 10 cm

Type Warp Weft Weight (g/m2)

13 Light 73 57 14

13 Heavy 70 60 17

17 100 70 23

18 100 80 24

20 120 80 27

22 120 100 30

24a 120 120 32

24b 140 100 32


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dressing pads sometimes suitably coated with a poly-mer to reduce adherence at dressing change.

The types as defined in the above table are derivedfrom the European Pharmacopoeia and the desig-nation of type numbers is one-tenth of the sum ofthe threads in warp and weft.

Cellulose sponge

Cellulose sponge is a cavity foam cellulose-basedsponge available in sheets and thin bands, used toabsorb at small sites in surgery. The material is notradiopaque and has a tendency to lose particles;additional precautions must therefore be taken if suchsurgical use is contemplated.

Neuropatties

Neuropatties are small squares or strips of non-wovenabsorbent viscose with thread stitched through thenon-woven fabric and left long. These are used as spotabsorbents particularly in neurosurgery. Products varyin size and shape and there may also be a device forattaching the ends of all the threads thus producing amini count rack.

Fibrous and Fabric Absorbents

Gauze and cellulose wadding

Gauze and cellulose wadding consists of a thick layerof cellulose wadding enclosed in a tubular form gauze.The properties of the two separate materials havealready been described. Combined, the gauze andcellulose wadding tissue is used as an absorbent andprotective pad. It should only be used as a wounddressing with a non-adherent layer placed betweenthe pad and the wound. On a highly exuding surface,there is a tendency for the cellulose wadding elementto collapse when wet and become a semisolid wet mass.This may cause difficulty in practice.

Gauze and cotton tissue(Gamgee tissue)

Gauze and cotton tissue (Gamgee tissue) is a thicklayer of absorbent cotton enclosed in a tubular gauze.It has the same uses as gauze and cellulose waddingtissue but has the advantage of a higher absorbentcapacity and less wet collapse. It is also softer in useand thus conforms more readily to the wound surface.It should be used in place of gauze and cellulose wad-ding tissue on high exudating surfaces such as burns

but should not be used in direct contact with thewound surface.

WOUND DRESSING PADS

These products are widely available in a number of for-mulations including the fibrous and fabric absorbentspreviously described, plus other materials combinedto meet some aspects of the acceptable performanceprofile.

The pads can be subdivided into:

� Absorbents and filmated products� Sleeved pads with a single layer core� Sleeved pads with a multiple layer core� Low adherence pads

The absorbents and filmated products have beendescribed. The simplest sleeved pads contain cotton,viscose, or cellulose fiber with an outer sleeve of gauzeor non-woven material. Those with a multilayer corehave an outer sleeve of cotton, viscose, or non-wovenfabric that may have been treated with a polymer suchas polypropylene to reduce adherence. Delayed ‘‘strikethrough’’ is facilitated by using a fluid retardant layerwithin the upper and outer sleeve that encourageslateral movement of fluid within the pad.

Low Adherence Pads

Low adherence pads have wound contact facesdesigned to be of low adherence. They vary fromaluminum-coated fabrics to perforated polymeric filmsor heat bonded polyethylene films. The wound contactfilm may be attached to an absorbent fibrous mat andan outer woven or non-woven fabric. In some pro-ducts, the polymeric film forms a continuous sleeveon both dressing surfaces. They are dressings for lowexudate and drying wounds where high adherencecan be expected. These low adherence, low absorptivecapacity dressings are sometimes centered on anadhesive backing to produce an ‘‘island’’ dressing usedas a postoperative adhesive dressing or, more famil-iarly, as a ‘‘first aid’’ island or strip dressing forsuperficial injuries.

LOW ADHERENCE PRIMARY DRESSINGS

These dressings consist of a partially open cell struc-tured nylon or viscose fabric that may be finished witha silicone coating. The open cell structure allows fluidtransmission to a superimposed absorbent dressing


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pad. This pad is changed when necessary and withoutdisturbing the primary contact layer.

Deodorizing Dressings

These dressings have been formulated from the highgaseous sorptive material, activated charcoal presentedas a woven fabric or a fibrous mat backed by a nylonsleeve, a vapor permeable film or a polyurethane foam.In each formulation, the objective is to reduce odorand the dressings must therefore be large enough tocover the entire malodorous area. One productencourages direct contact of the carbon layer withthe wound exudate, and whilst this will limit gaseousabsorption it is claimed that the incorporation ofbound silver into the charcoal cloth inactivatesbacteria adsorbed onto the fabric surface, therebyreducing the infective level and leading to a reductionof odor.

Polymeric Dressings

Vapor permeable adhesive films

Vapor permeable adhesive films are of use in thosewounds in which granulation tissue is established andwound exudate is declining.[14] These products weredeveloped as materials that would, in part, mimic theperformance of skin. The resultant products weretransparent, synthetic adhesive films genericallydescribed as vapor permeable adhesive membranes,and comprised of transparent polyurethane or othersynthetic films of low reflectance, evenly coated onone side with a synthetic adhesive mass. The adhesiveis cohesive and inactivated by contact with moistureand will not therefore stick to moist skin or the woundbed. The films are permeable to water vapor, oxygen,and carbon dioxide but occlusive to water and bacteriaand have highly elastomeric and extensible properties.They are conformable, resistant to shear and tear,sterile and particle free.

Removal of the stratum corneum results in a watervapor loss from tissues of between 3000 and 5000 g m2

over a period of 24 hr. This loss will result in progress-ive dehydration; of great significance, particularly in afull thickness burn. The water vapor loss through apositioned vapor permeable membrane is reduced to2500 g m2 over 24 hr—or less, depending upon thestructure of the membrane. Excess fluid is lost by watervapor transmission through the membrane; dehy-dration is minimized and a moist wound interface ismaintained. Where the volume of exudate producedis significantly greater than the volume removed asvapor, the water impermeability will result in serous

effusion accumulating below the film. Impermeabilityto water prevents wetting from external sources.

The importance of a moist interface to wound heal-ing is now well recognized. It allows the rapidmigration of new epithelium across the wound surface,precludes trauma due to adherence at dressing changeand contributes to gaseous diffusion in the damagedtissue. Oxygen and carbon dioxide transfer are accom-plished by intramolecular diffusion through the mem-brane and by solution in the wound surface moisture.The oxygen permeability of the films is variouslydescribed as 4000–10,000 cm3/m2 over 24 hr at ambientatmospheric pressure. The pO2 and pH levels of thewound surface are directly related to the gaseouspermeability and contribute to cellular activity. Thewound is protected against secondary infection bythe bacterial impermeability of the film to such organ-isms as Pseudomonas sp., S. aureus and E. coli.

Film dressings are used in the treatment of a widerange of conditions, including pressure ulcers, burns,abrasions, and donor sites. In a dermabrasion, hemo-stasis must first be obtained and the margin of thewound dried before the film is applied. In its appli-cation for the treatment of burns, careful disinfectionmust precede the positioning of the film and it is onlyrecommended for application to superficial and clini-cally clean burns. The use of films is contraindicatedfor deep burns as they retard the separation of necrotictissue.

Decubitus ulcers and pressure sores can be coveredwith a vapor permeable film. The films’ resistance toshear and low frictional surface properties protect thedermal layers from additional physical abrasion whileproducing the minimal barrier to normal skin functionwhich allows them to be used as a prophylactic in areasthat are traumatized by pressure but not ulcerated.

Film dressings can also be used for the retention ofcannulae and tubes in both ward and theatre. Specificproducts have now been produced with a variablewater vapor permeability to reduce the build up ofmoisture beneath the film and the resultant infectivehazard.

Recently, film dressings impregnated with an anti-bacterial (silver) for the management of infected woundsor a deodorizer (charcoal) for malodorous wounds havebeen introduced.

Polymeric foams

Polymeric foam dressings are a diverse group of pro-ducts with a wide range of properties. At their simplest,they are foamed polymers that have been made intosheets. The wound contact layer is often heat treatedand pressure modified to produce a hydrophilic porousmembrane about 0.5 mm thick to give a smooth, non-adherent wound contact surface that absorbs fluids by


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capillarity. The outer surface of the dressing is com-prised of a layer of relatively large cells of approxi-mately 5 mm thick that remain hydrophobic. Theirabsorbency and water vapor permeability are variedeither by a physical modification to the foam orby combining the foam with an additional sheetcomponent.

Foaming the polymer creates small, open cells thatare able to hold fluids and the cell size may be con-trolled during the foaming process. The most commonpolymer used is polyurethane. Their structure and soft-ness also provide a cushion that protects and contri-butes to thermal insulation of the wound. They alsomay be tailored for particular applications such as tra-cheostomy dressing without particle loss to the woundand with the retention of their conformable character-istics. The non-adhesive foams will require a secondarydressing.

The dressings are also available as in situ formedfoams, adhesive island dressings, and cavity filler[14]

and are suitable for wounds with moderate to heavyexudation.

Absorption of serous exudate is limited to the wound/dressing interface. In use, the absorptive capacity ofthe hydrophobic portion will be exceeded in a highexudate wound and, although moisture vapor trans-mission occurs through the dressing, frequent changesmay be required until the exudate level diminishes.The dressing combines the function of absorbencywith that of producing an acceptable microenviron-ment to allow healing to take place at the fastestrate concomitant with the total clinical condition ofthe patient.

Polyurethane foam dressings of this type are recom-mended for the management of dry sutured wounds,minor lacerations, early pressure ulcers, and venousulcers.[15,16]

Foams have been formulated with differing absor-bencies designed specifically for the management ofstasis ulcers and burns. The foam designed for themanagement of burns has dressing as the prime func-tion of absorbency. It consists of a highly absorbenthydrophilic polyurethane foam backed with a moisturepermeable polyurethane membrane and bonded to anapertured polyurethane net on the wound contact face.The backing whilst permeable to water vapor is imper-meable to water thus avoiding strike through. As theexudate level decreases, the membrane retains moistureand prevents the drying of the wound. The aperturedpolyurethane net interface reduces adherence to thewound surface.[17]

Low absorptive capacity primary foam dressingshave been produced from a carboxylated styrene buta-diene rubber latex foam. The foam is bonded to a non-woven fabric coated with a polyethylene film which hasbeen vacuum ruptured. The basic foam is naturally

hydrophobic and a surface active agent is incorporatedto facilitate the uptake of wound exudate. The dressingis recommended for minor wounds and abrasionswhere exudate levels are low and adhesion is a promi-nent hazard at dressing change.

In situ foam

This foam has been indicated for the management ofpilonidal sinus, hydradenitis suppurativa, perianal,and perineal wounds and in the management ofdehisced abdominal wounds.

It is necessary to occlude the cavity by packing toabsorb excess exudate and to stimulate the productionof granulation tissue, neovascularization, and collagendeposition.

An in situ formed foam was originally designed byDow Corning and found to be clinically superior toribbon gauze for cavity wound packing.[18] Its statusin cytotoxic terms was in dispute but it is now availableand its exclusion would be to the detriment of thisentry.

The cavity foam dressing is a two-part foam com-posed of a filled polydimethylsiloxane base and astannous octoate catalyst. The two components aremixed together immediately prior to use. The reactionis slightly exothermic, and over a period of 2–3 min thedressing expands to approximately four times its orig-inal volume and sets to a soft, spongy foam accuratelyconforming to the contours of the wound cavity. Thestent is normally removed twice daily, soaked in a mildantiseptic (0.5% aqueous chlorhexidine) rinsed in coldrunning water, squeezed dry, and replaced. A newdressing is formed after a week or more to match thereduction in size of the cavity. The product does notadhere to granulation tissue whilst maintaining freedrainage around the wound, and it has a low, but sig-nificant, absorptive capacity at the dressing surface.

Hydropolymer

This material appears visually as a foam but isdescribed as a foamed gel designed to expand intothe contours of the wound as it absorbs fluid. It is usedin an island configuration with a unique adhesive por-tion. It has the ability to readhere once lifted enablingmanipulation of the product for fit or assessment of thewound without dressing change. The hydropolymerwicks fluid into the upper layers of the dressing whereit escapes through the backing.[19]

Hydrogels

Hydrogels, or water polymer gels, are modified, cross-linked polymeric formulations which formthree-dimensional networks of hydrophilic polymers


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prepared from materials such as gelatin, polysac-charides, cross-linked polyacrylamide polymers, poly-electrolyte complexes, and polymers or copolymersderived from methacrylate esters. These interact withaqueous solutions by swelling to an equilibrium valueand retain a significant proportion of water withintheir structure. They are insoluble in water and areavailable in dry or hydrated sheets or as a hydratedgel in delivery systems designed for single use.

The physical properties of bulk polymers aredirectly influenced by a number of factors includingthe nature of monomers, copolymers, the cross-linkersand degree of cross-linking, and the polymerizationinitiators and processing parameters. The availabilityof hydrophilic and hydrophobic sites is influenced bythe chain of configuration and conformation and coulddetermine the degree of hydrophilicity and oxygenpermeability. By varying the nature of the polymerbackbone, a range of water binding behavior and thusmechanical, surface, and permeability properties canbe obtained. The expanded nature of the hydrogelstructure and its permeability allows the extractionand polymerization of initiator molecules, initiatordecomposition products, and other extraneous materi-als from the gel network before the hydrogel is placedin contact with the living system. The tissue-likestructure of most hydrogels will contribute to their bio-compatibility by minimizing mechanical irritation tosurrounding cells and tissues. They possess low interfa-cial free energies with aqueous solutions and only aweak tendency to absorb biological species such asproteins or cells. Their high moisture content (up to96% w/w when hydrated) maintains a desirable moistinterface which facilitates cell migration and preventsdressing adherence. Water can be transmitted throughthe saturated gel whilst the unsaturated gel will havewater vapor permeability comparable with the watervapor permeability of vapor permeable membranes.

The absorption, transmission, and permeability per-formance result in the maintenance of a moist woundwith a continuous moisture flux across the dressingand a sorption gradient that assists in the removal oftoxic components from the wound area. The highmoisture content allows dissolved oxygen permeability(which varies between products) to ensure the continu-ation of aerobic function at the wound/dressing inter-face and have an effect upon both epithelization andbacterial growth. It has been observed that the posi-tioning of a hydrogel frequently results in a markedreduction in pain response in patients. It is suggestedthat the high humidity protects the exposed neuronesfrom dehydration and also produces acceptablechanges in pH. A secondary effect, which may contrib-ute to this response, is the property of the gels toimmediately cool the wound surface and maintain alower temperature for up to 6 hr.[20]

Sheet hydrogels

These dressings are sheets of three-dimensional net-works of cross-linked hydrophilic polymers (polyethyl-ene oxide, polyacrylamides, polyvinylpyrrolidone,carboxymethylcellulose, modified corn starch). Theirformulation may incorporate up to 96% bound water,but they are insoluble in water and they interact bythree-dimensional swelling with aqueous solutions.The polymer physically entraps water to form a solidsheet and they have a thermal capacity that providesinitial cooling to the wound surface. A secondarydressing is required.

The recommendation for use of these productsincludes the management of donor sites and superficialoperation sites and also the treatment of freshlydamaged epithelium such as that seen with thermaland other painful wounds and dermatitic skin wherethe avoidance of topical agents is indicated. In chroniculcers, they are used to encourage granulation andformation of cellular tissue.

Amorphous hydrogels

Many of these hydrogels have additional ingredientssuch as alginate, collagen, or complex carbohydratesbesides water and a polymer. They are similar in com-position to sheet hydrogels but the polymer has notbeen cross-linked. These amorphous preparations donot have the cooling properties of the sheet dressingsand a secondary dressing is required. Their recom-mended use includes hydration of dry, sloughy, ornecrotic wounds and autolytic debridement.

A primary hydrogel dressing has been producedfrom a colloidal suspension of radiation cross-linkedpolyethylene oxide and water with an equilibriumwater content of 96%. The gel is sandwiched betweenpolyethylene films. The wound contact film is routinelyremoved and the outer film is used to control evapor-ation from the surface of the gel.[21,22] A novel hydrogelwas developed by the Max Plank Institute for Immu-nobiology and Dermatology consisting of an insolublecross-linked polyacrylamdie agarose polymer contain-ing 95% water as the dispersion phase.[23] This gel isavailable in hydrated and dehydrated forms and asgranules that, with their increased surface area, absorblarger amounts of exudate. The granules can be used tofill a cavity wound with the gel sheet superimposed toproduce a continuous hydrogel dressing.

An alternative to the acrylamide-based compositehydrogel dressing is an acrylamide grafted to a poly-urethane film to give a transparent, flexible gel withan equilibrium water content of approximately 50%.The hydrated gel has a low modulus of elasticity anda high water permeability that facilitates the adherenceof the gel to the wound surface. The permeability


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characteristics allow penetration of antimicrobialagents that can be applied topically to the dressingsurface in situ.

PARTICULATE AND FIBROUS POLYMERS

This group of dressings includes synthetic, semisyn-thetic, and naturally occurring products embracing arange of polysaccharide materials.

Xerogels

The xerogel dressings may be regarded as a subgroupof products within the larger group of polysaccharidedressings. The latter contains the well known cellulosicdressing products such as gauze and absorbent cotton(see ‘‘Absorbents’’ section) but the products whichconsist of dextranomer beads, dehydrated hydrogelsof the agar/acrylamide group, calcium alginate fibers,and dehydrated granulated Graft T starch polymersare identified specifically as xerogels,[24] the materialremaining after the removal of most or all of the waterfrom a hydrogel (or the disperse phase from any typeof simple gel). These materials have no water in theirformulation but swell to form a gel when in contactwith aqueous solutions.

Particulate Polymers

Dextranomer

This xerogel is a polymer of the polysaccharide dex-tran, a naturally derived polymer of glucose producedby cultures of a micro-organism, Leuconostoc mesen-teroides. The gel is formed when the dextran moleculescomprising the disperse phase of the hydrocolloid arecross-linked by a chemical process utilizing epichloro-hydrin and sodium hydroxide.[24] Dextranomer isavailable as beads or paste. The material requires asecondary dressing.

The dextranomer is supplied in beads of 100–300 mmdiameter containing poloxamer 187, polyethyleneglycol 300, and some water. A paste formulation is alsoavailable which is the dextranomer in polyethyleneglycol 600 (PEG 600). The beads are offered as a dis-crete particle or enclosed in a low adherence pouchfor insertion into a cavity wound. One company(Pfizer) offers a polymeric net which can be placed intoa cavity wound before the addition of either granulesor paste and facilitates removal and also a vapor per-meable film which is superimposed on the dextranomerdressing to control evaporation and retard drying in alow exudating wound.

Dextranomer has a pore size that produces anexclusion limit of 1000–8000 Da, which precludes thesorption of viruses and bacteria. Micro-organisms areremoved from the wound by the capillary actionbetween the beads, a function that is absent from thepaste formulation, which however demonstrates amarked increase in absorbing capacity for malodorouselements and pain producing compounds releasedduring the inflammatory response.

It is used primarily as a debriding agent on sloughyand exuding wounds, whether clean or infected, and onsmall area burns where the objective is to produce aclean tissue bed for the production of a granulatingtissue. It is not a product that should be usedbeyond this phase, as its continued application willimpair epithelization. Dextranomer is not biodegrad-able and both granules and paste must be carefullyremoved with Normal saline before drying to avoidparticulate residues and the subsequent developmentof granulomas.

Fibrous Polymers

Alginate dressings

Alginic acid is a polyuronic acid composed of residuesof D-mannuronic acid and L-guluronic acid and isobtained chiefly from algae belonging to the Phaeo-phyceae, mainly species of Laminaria.

Calcium alginate dressings are flat, non-woven padsof either calcium sodium alginate fiber or pure calciumalginate fiber. The alginate wound contact layermay be bonded to a secondary absorbent viscosepad. Alginate hanks and ribbon are also available aspacking for deeper cavity wounds and sinuses. Algi-nates have been shown to be effective in the manage-ment of injuries where there has been substantialtissue loss. The non-adhesive formulations require asecondary dressing.

Gel formation is via ion exchange of sodium inserum for calcium within the alginate dressing. A bio-degradable gel is formed when the fiber is in contactwith exudate, and the released calcium contributes tothe clotting mechanism. The gel may be firm or softdepending upon the proportions of calcium andsodium in the fiber. It is removed with saline.

The isomeric acids are present in varying propor-tions depending upon the seaweed source. The guluro-nic acid forms an association with calcium providingthe stimulus to produce the continuous disperse phaseof a hydrogel. Calcium ions and a phospholipid surfacepromote the activation of prothrombin in the clottingcascade. Calcium alginate products are used as thesource of these ions to arrest bleeding, both in super-ficial injuries and as an absorbable hemostat in


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surgery. The rate of biodegradation is related to thesodium/calcium balance in the preparation.

The dressings may be removed with a sterile 3%sodium citrate solution followed by washing with ster-ile water or they may be removed with sterile Normalsaline.

The ‘‘wet’’ integrity of the dressing which facilitatesremoval from the wound may be improved by incor-porating fibers of greater strength such as viscose(rayon) staple fiber or fibers which interact with thealginate fibers when wet such as chitosan staplefibers.[25]

The primary hemostatic usage of calcium alginate isin the packing of sinuses, fistulae, and bleeding toothsockets. The alginate dressings have recently becomewidely used as soluble wound packing for a numberof additional wound types. They have been used asuseful non-adherents for lacerations and abrasionsand are effective in the management of hypergranula-tion tissue (proud flesh), interdigital maceration, andheloma molle. Their hospital and community useincludes intractable skin ulcers and pressure ulcers,where they would appear to accelerate healing; andin the successful management of diabetic ulcers, venousulcers, burns, and infected surgical wounds.

Alginates have proved to be useful debriding agents.When applied to these injury types, the alginate mustbe covered by a secondary dressing of foam or film.Some proprietary products bond calcium alginate toa secondary backing such as absorbent viscose pador semipermeable adhesive foam to produce an islanddressing.

Hydrocolloids

Hydrocolloid dressings consist of composite productsbased on naturally occurring hydrophilic polymers.Generally, these dressings are flexible, highly absorb-ent, occlusive or semiocclusive adhesive pads formu-lated from biocompatible, hydrophilic polymers suchas sodium carboxymethylcellulose, hydroxyethylcellu-lose pectins, and gelatin incorporated into a hydro-phobic adhesive. The dressings may be backed by apolymeric film and may be contoured to fit difficultareas. Hydrocolloids are also available as pastes orpowders or gels. The pads do not require a secondarydressing.

In general, they consist of a pressure sensitiveadhesive layer which is composed of a so-called‘‘hydrocolloid’’ dispersed with the aid of a tackifierin an elastomer and secondly a film coating composedof a gas permeable but water impermeable, flexible,elastomeric material. A currently available hydro-colloid dressing is a flexible mass with an adherentinner face and an outer semipermeable polyurethanefoam.

The formulation is:

Sodium carboxymethylcellulose 20%

Polyisobutylene 40%

Gelatin 30%

Pectin 20%

The product is also available as granules of similarformulation, which allows larger cavity wounds andheavily exuding wounds to be treated with a continu-ous hydrocolloid system.

Other hydrocolloid dressings with formulationsconsisting of sodium carboxymethylcellulose combinedwith karaya gum or sodium carboxymethylcellulose onits own are also available.

The adhesive formulation of hydrocolloids gives aninitial adhesion higher than some surgical adhesivetapes. After application, the absorption of trans-epidermal water vapor modifies the adhesive flow tomaintain a high tack performance throughout theperiod of use. In situ the dressings provide a gaseousand moisture proof environmental chamber stronglyattached to the area surrounding the wound and offer-ing protection against contamination from inconti-nence or other sources. In the wound contact area,the exudate is absorbed to form a gel that swells in alinear fashion with higher moisture retention at thecontact surface. This results in an expansion of thegel into the wound cavity with the continued supportand increasing pressure from the remainder of theelastomeric dressing. The advantage of this is that afirm pressure is applied to the floor of a deep ulcer,a basic surgical maxim for the production of healthygranulating tissue. It is this function that contributesto the recommended usage for venous leg ulcers.[26]

The formed ‘‘colloidal’’ gel also produces a sorptiongradient for soluble components within the serous exu-date thereby allowing the removal of toxic compoundsarising from bacterial or cellular destruction. However,during use, the dressing in contact with the woundliquefies to produce a pus-like liquid with a somewhatstrong odor.

Hydrocolloids are suitable for desloughing and forlight to medium exuding wounds—but are contraindi-cated if an anaerobic infection is present. They havebeen used successfully in the treatment of chronic legulcers, pressure ulcers, minor burns, granulatingwounds, and wounds exhibiting slough or necrotictissue or wounds with moderate exudate, as well asskin barriers in the management of stoma.

Superabsorbents

Superabsorbent hydrocolloid dressings have a highlyabsorbent capacity and entrap exudate so that it


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cannot be squeezed out once absorbed. One productincorporates the highly absorbent material into anisland pad covered by a non-woven absorbent and sur-rounded by an extra thin hydrocolloid as the adhesiveportion. The covering acts as a transfer layer while itssurface stays dry. This is used for heavily exudingulcers.[14]

Hydrofibers

Hydrofibers are fibers of carboxymethylcelluloseformed into flat, non-woven pads. It is produced as atextile fiber and presented in the form of a fleece heldtogether by a needle bonding process, and is availableboth as a ‘‘ribbon’’ for packing cavities, and as a flatnon-woven pad for application to larger open wounds.The dressing absorbs and interacts with wound exu-date to form a soft, hydrophilic, gas-permeable gel thattraps bacteria and conforms to the contours of thewound whilst providing a microenvironment that isbelieved to facilitate healing. The resultant gel is simi-lar to a sheet hydrogel but it does not dry out or wicklaterally. Therefore, there is no maceration of the skinsurrounding the wound. The high absorbent capacityreduces the frequency of dressing changes.

Sheet formulations may be applied to exudinglesions including leg ulcers, pressure areas, donor sites,and most other granulating wounds, but for deepercavity wounds and sinuses the ribbon packing is gener-ally preferred. The dressing is easy to remove withoutcausing pain or trauma, and leaves minimal residueon the surface of the wound.[14]

IMPREGNATED DRESSINGS

Originally, these materials were formulated to coat thearea of the wound with hydrophobic paraffin spreadon an open mesh gauze thereby providing both insu-lation and partial occlusion but allowing excess exu-date to be absorbed by a superimposed absorbentpad. The products had the advantage of low adherenceand allowed gaseous diffusion, but the disadvantagesincluded the incorporation of the soft paraffin orloose cotton fibers into the healing wound therebyleading to an extended inflammatory phase with conse-quent delayed wound healing. These products also,when used excessively, retained wound exudate causingmaceration to the surrounding, otherwise healthy,tissue.

Paraffin Gauze (Tulle) Dressing

Paraffin gauze is bleached cotton or combined cottonand rayon cloth impregnated with yellow or white soft

paraffin. It is available as sterile single pieces or multi-packs. The paraffin is present to prevent the dressingadhering to a wound. The gauze that may be leno innature is coated so that all the threads of the fabricare impregnated but the spaces between the threadsare free of paraffin. The material is used primarily inthe treatment of wounds such as burns and scaldswhere the protective function of the stratum corneumis lost and water vapor can escape. Paraffin gauzedressing functions by reducing the fluid loss whilstthe water barrier layer is reforming.

In addition to burns and scalds, the dressing is usedas a wound contact layer in lacerations, abrasions, andin ulcers where it is used as a packing material topromote granulation. Postoperatively, it is used as avaginal or penial dressing and for sinus packing.

Povidone iodine 10%, chlorhexidine 0.5% w/w,sodium fusidate 2% w/w, and 1% framycetin sulfateare examples of available gauze impregnations andare recommended for the reduction of wound infec-tion. However, diffusion of the antibacterial agent intoor onto an infected and exuding wound has beenshown to be minimal and the possibility of develop-ment of resistant strains of infective organisms hasreduced the usage of these products.

Silver Dressings

Advanced wound management products containingsilver have been developed to treat difficult-to-healwounds, chronic ulcers, and extensive burns. Nano-crystalline silver represents a new format of the metalfor use in wound management. Silver is a broad-spectrum antibiotic active against such organisms asPseudomonas sp., S. aureus, E. coli, and Candidaalbicans and to which there has been little reportedevidence of resistance. Although silver is an efficientantimicrobial, its use has been limited because of thedifficulty of delivering it to the tissues. Nanotechnol-ogy has overcome this as it allows for the building ofchemical compounds one atom at a time. A nanocrys-talline structure gives a greater surface area for, in thisinstance, silver release.

Free silver ions are the active components of anti-microbial silvers, and it has been shown that as littleas one part per million of elemental silver in solutionis an effective antimicrobial. Materials such as poly-mers, charcoal, and hydrocolloids when formulatedwith silver not only aid wound management and heal-ing but also regulate its release into the woundenvironment and surrounding tissues. Silver ions killmicro-organisms by inhibiting cellular respiration andcellular function.[27–30] It is known that their mode ofaction is exerted by binding cysteine residues onthe cell walls of yeasts such as C. albicans thereby


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inhibiting the enzyme phosphomannose isomerase(PMI).[31] This enzyme is essential for the synthesis ofthe cell wall and without it phosphate, glutamine,and other nutrients are released from the cells. Phos-phomannose isomerase was not inhibited by silver inE. coli cultures.[31] In a wound environment, silvercombines with proteins, cell surface receptors, andwound debris.[31]

It has been suggested that some nanocrystallinesilver products release a cluster of silver ions andradicals, which are highly antibacterial because ofunpaired electrons in outer orbitals. Silver and silverradicals released from these products are reported toact by impairing electron transport, inactivating bac-terial DNA, cell membrane damage, and binding andprecipitation of insoluble complexes.[32]

Advanced wound management products containingsilver have been developed to treat difficult-to-healwounds, chronic ulcers, and extensive burns. Odorabsorbing dressings adsorb polarized bacteria ontothe surface of the charcoal cloth used in the formu-lation. The silver present in the dressing exerts a bac-tericidal effect that gradually diminishes as woundexudate saturates the material.

Silicones

Silicones are long chain polymers comprised of alter-nate atoms of silicone and oxygen with organic groupsattached to the silicon atoms. The degree of polymeri-zation determines the physical form of the silicone.Soft silicones are a particular family of solid siliconesthat are soft and tacky. These properties enable themto adhere to dry surfaces. A soft silicone dressing iscoated with soft silicone as an adhesive or wound con-tact layer and may be removed without trauma to thewound or surrounding skin. Silicone dressings havebeen used clinically as an alternative to paraffin gauzefor the fixation of pediatric skin grafts where it wasfound that changing the outer absorbent dressingwas painless as was the removal of the siliconedressing itself so that no analgesia or anesthesia wasrequired.[33]

Generally, silicone dressings have a porous, semi-transparent wound contact layer consisting of a flex-ible, polyamide net that is coated with silicone. Thedressing is non-absorbent but the pores within itsmatrix allow the passage of exudate from the woundto the secondary dressing. Its use is limited to minorskin grafts because the dressing requires a margin ofhealthy skin for application of at least 2 cm surround-ing the wound.

Silicone dressings have also been used to managewounds generated by radiotherapy, fingertip injuries,severe mycosis fungoides, and epidermolysis bullosa.

The silicone material needs to be kept in intimatecontact with the surface of the wound to functioneffectively which means that wounds in convex areaspresent few problems whereas those on concave,jointed, or contoured areas need adequate padding tobe applied to exclude voids beneath the dressing whereexudate could accumulate. As silicone is an inertmaterial, it has been shown that, where clinically indi-cated, topical steroids or antimicrobial agents can beapplied either over or under the silicone material with-out diminishing their efficacy.

There have been reports indicating that use of sili-cone dressings leads to improvements in the appear-ance (scar size, erythema, elasticity) and symptoms(pruritis, burning pain) after application to hyper-trophic scars and keloids.[34] Silicone dressings arethought to effect this by promoting hydration of thescar and applying pressure, thereby flatteningscar tissue, increasing wound elasticity, and reducingdiscoloration.

Tissue Adhesives

Tissue adhesives are formulated from cyanoacrylatecompounds such as bucrylate, enbucrilate, or mecry-late which polymerize in an exothermic reaction oncontact with a fluid or basic substance to form astrong, flexible, and waterproof bond. They are synthe-sized by reacting formaldehyde with alkyl cyanoacetateto obtain a prepolymer, which may be depolarized to aliquid monomer by heat. This monomer may then bemodified by altering the alkoxycarbonyl (–COOR)group of the molecule to give compounds of differentchain lengths.

Tissue adhesives are generally applied to simplelacerations where they give similar cosmetic resultsto suturing. It is essential that the wound edges areaccurately apposed to ensure that no adhesive passesbetween them. There have been no reports of carcino-genicity or toxicity when they are used topically. Theyshould not be used over joints as repetitive movementwill cause the adhesive to peel off.

BIODRESSINGS

Biodressings are composed of materials almost exclus-ively originating from living tissue and are said to‘‘participate actively and beneficially in the biochemis-try and cellular activity of wound ‘‘healing.’’[35]

They can be identified as biological dressings andbiosynthetic dressings and the biological dressingscan be further subdivided into natural or cultured—depending upon their origin.


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Collagen Dressings (Biosynthetic Dressings)

These dressings are formed from denatured collagenpeptides derived from pigskin and purified bovine hidecollagen cross-linked with the glycosaminoglycan,chondroitin-6-sulfate, and freeze dried. When appliedto damaged tissue, the dressings stimulate the produc-tion of fibroblasts and endothelial cells whilst acceler-ating the migration of epithelial cells. These biologicalcomponents are combined with silicone elastomers tocontrol moisture vapor loss during the acceleratedgrowth period.[36]

The bovine material used for the extraction of theType 1 collagen used in these dressings is non-antigenicdue to enzymatic purification. The bovine Type 1 col-lagen is in a triple helical form and may be combinedwith oxidized, regenerated cellulose. The collagen helixmay be attached to a non-adherent backing and, there-fore, these materials require a secondary dressing.Addition of collagen to a wound bed may acceleratewound repair by the provision of a matrix for cellularmigration.[14]

They are available as sheets, particles, pastes, or gelsand the dry materials absorb exudate to form a gel.One manufacturer has incorporated 10% alginate inthe dressing formulation. These dressings are recom-mended for use on any recalcitrant wound free fromnecrotic tissue and showing no signs of infection.

‘‘Natural’’ Biological Dressings

Autologous (self) skin is harvested from a healthy areaof the patient’s body and transferred to the wound,generally a burn. The procedure leaves a second injuryor donor site. The advantages of non-allergenicity,non-toxicity, non-pyrogenicity, and direct incorpor-ation into the healed area with the overall performanceparameters of intact skin make this the dressing ofchoice.

Skin harvested from fresh cadavers and used as anallograft is a possible alternative to autologous skin.This skin undergoes processing to remove fibroblasts,endothelial cells, and epidermis, which would stimulatean immune response. The resulting product is an acel-lular, dermal collagen matrix which is immunologicallyinert but retains elastin, proteoglycans, and the base-ment membrane complex.[36]

Porcine Skin

Sterile, denatured lyophilized skin of porcine origin isproduced and consists of the dermal and/or epidermallayers. The material is reconstituted by immersion in

sterile water or saline before being applied dermal sideto the wound. It is used as a temporary dressing inburns and ulcers, particularly where a site is beingprepared for grafting.

‘‘Cultured’’ Biological Dressings

Cultured biological dressings are derived from mam-malian cell culture procedures which facilitate thedevelopment of sheets of cells derived from a few ofthe patients’ own epidermal cells. Cultured humankeratinocytes form cultured epithelial grafts that arenot bioengineered tissues but are cultured cell productswith limited use. These cultures may be regarded as aprecursor which has led to the development of otherproducts through bioengineering.[36]

Bilayered Skin Equivalent

A bilayered composite skin equivalent has beendeveloped with a viable dermis and epidermis. The epi-dermis is composed from cornified differentiated kera-tinocytes and a dermal matrix composed of a collagenlattice containing viable fibroblasts. Its cellular compo-nents assist with wound closure through stimulation ofthe wound bed. The outer layer of the differentiatedbilayered skin equivalent, the stratum corneum, actsas a specialized vapor permeable membrane and pro-tective outer barrier.[36]

Human Dermal Replacement

This material requires cultivation of human diploidfibroblasts on a three-dimensional polymer scaffold.The cells are derived from newborn foreskin and areliving cells which are metabolically active followingimplantation into the wound bed.[36]

Hyaluronic Acid

Vapor permeable adhesive films derived from materialsfound in some tissues are being used more commonlyin wound management. Most of the available filmsare composed of industrially manufactured and puri-fied benzyl ester derivatives of hyaluronic acid andmay be used for direct application to wounds such asdiabetic foot ulcers or venous leg ulcers or as scaffoldsfor the cultivation of fibroblasts and keratinocytes forfurther transplantation.


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BIOACTIVE DRESSINGS

The introduction described the performance param-eters of interactive dressings that distinguished themfrom the passive products. Current developments haveconfirmed that the next generation of products willparticipate ‘‘actively’’ in the wound healing processby contributing growth hormones, chemotactic agents,angiogenic agents, and other growth factors either in adepot release mode or as sequentially released com-pound[37] as well as controlling the microenvironmentsurrounding the wound.

Each wound management product will eventuallybe designed to meet the environmental, nutritional,and growth requirements of particular wound typesand will probably be based on those ‘‘biodressings’’described above. The group will be designated bioac-tive wound management products.[38] Bioactive dres-sings already include such materials as antimicrobialdressings, single component products of biological ori-gin, and combinations of both these. These ‘‘biodres-sings’’ must be the precursors for the development ofmany more exciting products that will improve themorbidity of wound healing to the advantage of bothpatient and clinician.

CONCLUSIONS

The content of this entry has been restricted to pro-ducts in direct contact with the wound. There are manyother products outside this limitation used successfullyfor wound management. These include surgicaladhesive tapes and non-extensible, conforming, andelastic net bandages, used to retain dressings in pos-ition, and the extensible bandages which may varyfrom the light support and compression products forthe management of sprains and strains and the preven-tion of edema, to the high compression bandages usedeither alone or superimposed on various dressings toapply pressure to a limb.

REFERENCES

1. Breasted, J. Edwin Smith Surgical Papyrus Facsimile;University of Chicago Press: Chicago, 1930.

2. Najano, G. The Healing Hand; Harvard University Press:Cambridge, MA, 1975.

3. Mackinney, L. Medical Illustrations in Medical Manu-scripts; Clowes and Sons: London, 1965.

4. Packard, F.R. Life and Times of Ambroise Pare; Milford:London, 1922.

5. Elliot, J.R. Surgical materials. St. Barts Hosp. J. 1954, 58,11–14.

6. British pharmacopoeia. HMSO: London, 1998.7. Winter, G.D. Formation of the scab and the rate of epithe-

lialisation of superficial wounds in the skin of the youngdomestic pig. Nature 1962, 193, 293–294.

8. Bull, J.P.; Squire, J.R.; Tophey, E. Experiments with occlu-sive dressings of a new plastic. Lancet 1948, 2, 213–214.

9. Turner, T.D. Hospital usage of absorbent dressings. Pharm.J. 1979, 22, 421–426.

10. Turner, T.D. Proceedings of the Symposium on WoundHealing, Helsinki, Sundell, B., Ed.; 1979; 75–84.

11. Lock, D.M. Proceedings of the Symposium on WoundHealing, Helsinki, Sundell, B., Ed.; 1979; 103–108.

12. Turner, T.D. Surgical absorbents. Afr. Health 1979, 1 (94),22–24.

13. Turner, T.D. Absorbents in surgery. Proceedings ofthe Guild of Public Pharmacists Conference, York, 1977;56–59.

14. Ovington, L.G. The well-dressed wound: an overview ofdressing types. Wounds 1998, 10 (Suppl. A), 1A–11A.

15. Dahle, J.S. Proceedings of the Symposium on WoundHealing, Helsinki, Sundell, B., Ed.; 1979; 143–154.

16. Banks, V.; Bale, S.; Harding, K.G.; Harding, E.F. A ran-domised, stratified, controlled, parallel-group clinical trialof a new polyurethane foam dressing (Lyofoam Extra)versus a hydrocellular dressing (Allevyn) in the treatmentof moderate to heavily exuding wounds. Proceedings of6th European Conference on Advances in WoundManagement; Leaper, D.J., Cherry, G.W., Dealey, C.,Lawrence, J.C., Turner, T.D., Eds.; Macmillan: London,1997; 235–238.

17. Thomas, S. The role of foam dressings in wound manage-ment. In Advances in Wound Management; Turner, T.D.,Schmidt, R.J., Harding, K.G., Eds.; John Wiley and Sons,Inc.: New York, 1986; 23–29.

18. Harding, K.G. Silastic foam. In Advances in WoundManagement; Turner, T.D., Schmidt, R.J., Harding, K.G.,Eds.; John Wiley and Sons, Inc.: New York, 1986;41–52.

19. Banks, V.; Fear, M.; Orpine, J.; Hogelstrom, S.; Colgate,G.; Humphries, J.; Disley, L.; Bale, S.; Thomas, S.;Harding, K.G. A comparative open multicentre trial ofTielle hydropolymer dressing and Granuflex improvedformulation. Proceedings of 5th European Conference onAdvances in Wound Management; Cherry, G.W., Gottrup,F., Lawrence, J.C., Moffat, C.J., Turner, T.D., Eds.;Macmillan: London, 1995; 163–167.

20. Turner, T.D. Pharm. Int. 1985, 6 (6), 131.21. Eaglestein, W.H. J. Am. Acad. Dermatol. 1985, 12,

434–440.22. Yates, D.W.; Hadfield, J. Med. Injury 1984, 16, 230–232.23. Myers, J.A. Pharm. J. 1983, 230, 263–264.24. Schmidt, R. Xerogel dressings. In Advances in Wound

Management; Turner, T.D., Schmidt, R.J., Harding, K.G.,Eds.; John Wiley and Sons, Inc.: New York, 1986; 65–72.

25. Gilchrist, T.; Mitchell, D.C.; Burrows, T.R. Sorbsan. InAdvances in Wound Management; Turner, T.D., Schmidt,R.J., Harding, K.G., Eds.; John Wiley and Sons, Inc.:New York, 1986; 73–82.

26. Turner, T.D. Royal Soc. Med. Symp. Series No. 38; 1985,5–14.

27. Monafo, W.; Moyer, C. The treatment of extensive thermalburns with 0.5% silver nitrate solution in early treatment ofsevere burns. Ann. N.Y. Acad. Sci. 1968, 150, 937.

28. Fox, C. Silver sulfadiazine: a new topical therapy for pseu-domonas in burns. Arch. Surg. 1968, 96, 184.

29. Wells, T.N.; Scully, P.; Paravicini, G. et al. Mechanismsof irreversible inactivation of phosphomannose isomerasesby silver ions and flamazine. Biochemistry 1995, 34, 7896–7903.

30. Schreurs, W.J.; Rosenberg, H. Effect of silver ions ontransport and retention of phosphate by Escherichia coli.J. Bacteriol. 1982, 152, 7–13.

31. Ovington, L.G. Nanocrystalline silver where the old andfamiliar meets a new frontier. Wounds 2001, 13 (Suppl.B), 5–10.

32. Thurman, R.B.; Gerba, C.P. The molecular mechanisms ofcopper and silver ion disinfection of bacteria and viruses.CRC Crit. Rev. Environ. Control 1989, 18, 295–315.


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33. Platt, A.J.; Phipps, A.; Judkins, K. A comparative study ofsilicone net dressing and paraffin gauze dressing in skingrafted sites. Burns 1996, 22 (7), 543–545.

34. Mustoe, T.A.; Cooter, R.D.; Gold, M.H.; Hobbs, F.D.R.et al. International clinical recommendations on scar man-agement. Plast. Reconstr. Surg. 2002, 110 (2), 560–571.

35. Lofts, P.M. Biodressings. In Advances in Wound Manage-ment; Turner, T.D., Schmidt, R.J., Harding, K.G., Eds.;John Wiley and Sons, Inc.: New York, 1986; 127–131.

36. Mulder, G.T. The role of tissue engineering in wound care.J. Wound Care 1999, 8 (1), 21–24.

37. Turner, T.D. Wounds 1989, 1 (3), 155–179.38. Turner, T.D. Surgical dressings and their evolution. Pro-

ceedings of 1st European Conference on Advances inWound Management; Leaper, D.J., Harding, K.G., Turner,T.D., Eds.; Macmillan: London, 1992; 181–187.

BIBLIOGRAPHY

An Environment for Healing; Royal Soc. Med. Int. Cong. Series,No. 88; 1984.

Goldsmith, L.A., Ed.; Biochemistry and Physiology of the Skin;Oxford University Press, 1983; Vols. 1 and 11.

Leaper, D.J.; Harding, K.G., Ed.; Wounds: Biology and Man-agement; Oxford University Press, 1998.

Peacock, E.E. Wound Repair; WB Saunders: London,1984.

Turner, T.D.; Schmidt, R.J.; Harding, K.G., Ed.; Advances inWound Management; John Wiley and Sons, Inc.: New York,1986.

Westaby, E.S., Ed.; Wound Care; William Heinemann MedialBooks: London, 1985.


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Drug Abuse

Richard B. SeymourDavid E. SmithHaight Ashbury Free Clinics, San Francisco, California, U.S.A.

INTRODUCTION

Drug abuse may manifest at one of several differentlevels. Habituation involves a distinct and possiblyharmful pattern of use. Drug abuse has been definedas a pattern of problem use that results in health con-sequences, social problems, or both. Drug addiction isa chronic disease of the brain that involves relapse,progressive development, and the potential for fatalityif not treated. Addiction cannot be cured but can bebrought into remission through a program of treat-ment, abstinence from all psychoactive substances,and supported recovery. In general, the drugs involvedin abuse of drugs are within the grouping of ‘‘psy-choactive’’ drugs. These are substances that have theirprimary effect on the brain and central nervous system(CNS) and include opioids, sedative–hypnotics, stimu-lants, and hallucinogens. Recent additions includeperformance-enhancing drugs, such as steroids, and com-binations producing the effects of several drug groups.

LEVEL OF DRUG USE AND ABUSE

Inaba and Cohen[1] list six levels of drug use and abuse.These are: 1) abstinence; 2) experimentation; 3)social/recreational; 4) habituation; 5) drug abuse; and 6)addiction. These levels may not be progressive fromone to the next, but will indicate in a progression con-text if the individual is developing a drug problem.

Abstinence

Abstinence means no use of psychoactive substances.However, in our culture, or for that matter in any cul-ture, psychoactive substances are virtually impossibleto avoid. Nearly all of us have experienced pain medi-cation. Most soft drinks, tea, and, of course, coffeecontain caffeine, a potent stimulant. Yet, individualswho partake of these will consider themselves abstinentand with few exceptions this use is marginal to thepoint of not being worth consideration.

In terms of potential drug abuse or addiction, thenominally abstinent person is in little danger. Develop-ment of abuse requires the initial use of potentdrugs. Addiction may involve a genetic vulnerability,but it also requires an environment that is conductiveto initial use, and that will be lacking in the consis-tently abstinent individual, so long as he or she remainsabstinent.

Drug Experimentation

Experimentation usually ensues when the individualbecomes curious about a drug’s effects or is influencedto try a drug by relatives, friends, coworkers or suchcues as advertising and word of mouth. Many youngpeople in the late 1950s and early 1960s tried mari-juana when it was offered to them. Although all theymay have heard about the drug in school, from par-ents, teachers, and other authority figures was highlynegative regarding the drug, they were curious as toits effects and that curiosity overrode the warnings thatthey had received.

Experimentation, however, involves no pattern ofuse and usually minimal negative consequences. Theindividual may use on occasion as the occasion pres-ents itself, but there is no drug-seeking behavior, andthe consequences are minimal. There are exceptions,however, and these may include:

� Using a large amount, such as binge drinking inhigh school or college under peer pressure, thatresults in accident, injury, or illness.

� An extreme physical reaction to a small amount ofdrug via an allergy or idiosyncratic reaction.

� Aggravation or triggering of a pre-existing physicalor mental condition.

� Use during pregnancy.� Use resulting in legal problems such as an arrest for

possession or loss of a job after failing a drug test or.� An addictive response from individuals with a very

high susceptibility to compulsive use triggeringimmediate abuse or addiction.

Encyclopedia of Pharmaceutical Technology DOI: 10.1081/E-EPT-100200039Copyright # 2007 by Informa Healthcare USA, Inc. All rights reserved.1038

Dressing in Wound Management

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