Moist wound healing, exudate andmanagement of the wound bedThis paper reviews the current state of thinking and evidence on moist wound healing,and presents a new wound <strong>dressing</strong> technology that enables the purported ‘optimum’moist environment to be maintained without risk of desiccation or macerationMartyn Butcher, Independent Tissue Viability Consultant, Plymouth, UKIn the past 40 years, the wound care communityhas embraced the concept of moist wound healingand the need for exudate management, butit still has not identified exactly how these conceptscan be used to create the so-called ‘optimum’ environment.While numerous wound <strong>dressing</strong>s purportto ‘effectively’ handle varying moisture levels,there is no robust evidence on what the ‘ideal environment’actually is in terms of moisture content.As a result, clinicians use empirical measures togauge their success in providing a moist woundenvironment. Effective exudate management, particularlyin relation to heavily exuding wounds,remains a clinical challenge.The ‘moist wound healing’ mantraIn modern times, it has been accepted that the optimumenvironment for the repair and restoration oftissue function is one in which the wound bed iskept moist. By providing a moist wound environment,it is possible to increase macrophage andfibroblast activity, re-epithelialisation and the productionof collagen. It has also been postulated thatmoisture is important in maintaining endogenousbioelectric fields, which orchestrate cell movementby galvanotaxis and the expression of specificgenomes that are important in the repair process. 1The presence of a moist wound environment,therefore, is an essential component of naturalwound healing. However, the definition of the optimalmoist environment lacks clarity, beingdescribed as ‘not too wet, not too dry’. 2 In ‘normal’acute wound healing models, the body’s owndefence system provides moisture in the form ofwound exudate. When exposed to the atmosphere,exudate dries to form a scab. This impairs re-epithelialisationas the migrating tissue has to movethrough or under the physical barrier presented bythe dry eschar. 3,4According to Fonder et al. 5‘One of the great misconceptions in wound care is thata wound heals best when permitted to form a dry scab.By contrast, moisture has repeatedly been shown tosignificantly accelerate wound healing. Emergency physiciansand other acute care providers are encouraged toincorporate occlusive moisture-retentive <strong>dressing</strong>s intotheir regular practice to expedite healing, reduce painand scarring, improve wound care convenience andpatient compliance, and minimise wound contaminationand infection’.Managing exudate: its meaning inthe healing regimenAs evident in wound management tools such aswound bed preparation and TIME, expert exudatemanagement is a key component of a structuredapproach to wound care. Clinicians face thedilemma of keeping the wound bed hydrated, whilealso eliminating any excess wound exudation.Excess exudation caused by systemic or regionalfactors, such as oedema or venous hypertension,needs to be addressed and, wherever possible,reversed. If the high levels of exudation persist,then complications can occur. This applies even tothe use of graduated compression bandages, whichcan rapidly become soiled; applying additionallayers of absorbent materials underneath themalters the limb circumference, thereby changingthe pressures achieved.Managing exudate:practical considerationsExudate production is not a linear event: exudatelevels rise and fall as a result of both internal andexternal influences. For example, the onset of infectionis often heralded by an increase in exudate 6 aslocal inflammation increases periwound capillarypermeability and, in turn, the volume of exudateproduced. In addition, the effects of gravitationalforces of venous pressure, when the individual is1 0J O U R N A L O F W O U N D C A R E S O R B I O N S U P P L E M E N T 2 0 1 0
upright or the affected limb isdependent, may also increase exudateproduction. It is possible toreduce capillary pressures by elevatingthe leg, but many people findthis impractical. Similarly, significantproblems are experienced with leakageand strikethrough when walkingor standing for periods of time.The wound location is thus highlysignificant, with lesions on the lowerlimb generally causing more exudate-relatedproblems than thosehigher up the torso. This is especiallysignificant when dealing with ulcerson the plantar surface of the foot. Chronic woundsin this area often have a diabetic neuropathic orneuroischaemic aetiology. Plantar ulcers pose additionalproblems for patients, who are invariablydependent, and management is difficult if mobilityis to be maintained.Managing exudate:the clinician’s dilemmaFailure to check a <strong>dressing</strong>’s fluid-handling propertiesbefore application can cause problems. Forexample, a high absorbency product mistakenlyused on a low to moderately exuding wound willresult in a dry (desiccated) wound bed, to which theproduct will adhere. Clinicians should therefore base<strong>dressing</strong> selection on the wound status and theirown clinical objectives. Consideration of exudatelevels plays a crucial role in this.In some instances — particularly in larger wounds— one area of the wound might have high levels ofexudation, while another part might be dry. Traditionally,one option for the clinician has been tocover the entire wound with a hydrogel <strong>dressing</strong> inorder to rehydrate the hardened eschar, whiletrying to prevent the exudation from other parts ofthe wound having a deleterious effect on healing.Conversely, the clinician may have decided to usean absorbent <strong>dressing</strong>, which could further desiccateany dry areas of the wound bed. This mighthave led the clinician to use multiple wound-careproducts on the same wound.This phenomenon, whereby layer upon layer of<strong>dressing</strong>s are applied, each with a desired outcomein wound management, complicates managementand increases costs. While hydrogels may rehydratedry eschar, many clinicians will have had littleunderstanding of whether they are of benefit whenused in conjunction with an alginate, which isintended to absorb excess exudate. Indeed, manyclinicians will have had limited understanding ofthe potential interaction of such a hybrid <strong>dressing</strong>,or whether one <strong>dressing</strong> will nullify the action ofanother. An unduly complicated and ultimatelycostly intervention would result, with little evidencethat it delivers any clinical benefit.Hydration response technologySorbion sachet S is constructed of selected andmechanically treated cellulose fibres within whichpolymer gelling agents are embedded (Fig 1). In theFig. 2Fig. 1presence of moisture, these compoundsinteract with and lock upfluid. The <strong>dressing</strong>’s actionensures maximum fluid-handlingwithout the risk of desiccation atone extreme or maceration at theother. 7 The manufacturer hasnamed this ‘hydration responsetechnology’ (HRT) and indicatesthis is a potential advancementin the management of woundfluid and the creation of an ‘optimalmoist wound environment’.The <strong>dressing</strong> is double-faced, soJ O U R N A L O F W O U N D C A R E S O R B I O N S U P P L E M E N T 2 0 1 01 1
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