Wound bed preparation - moisture management

The third component of wound bed preparation is moisture management which is accomplished with the application of carefully selected dressings based on both the wound and the patient function.

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Oct 27, 2019
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Maintaining a moist wound bed is universally accepted as the standard of care for promoting wound healing; however, managing wound drainage in such a way that the optimal moisture balance is achieved can be a challenge, especially in chronic wounds with moderate to heavy drainage.  Understanding the role of dressings, the composition of all the dressings currently on the market, and making the best selection for each patient at every dressing change can be daunting, even for the experienced clinician. 

Although there have been no absolute definitions of drainage amounts, the following are guidelines to use when documenting drainage and establishing outcomes:

Scant – barely any drainage visible on the side of the dressing next to the wound; none visible after dressing removal.

Minimum – drainage visible on the inner side of the dressing only; may be some visible on the wound bed after dressing removal; no new drainage expressed during treatment.

Moderate – drainage visible on the inner side and small amount on the outer side of the dressing; some drainage visible on the wound bed after dressing removal; some drainage occurring during prolonged treatments.

Heavy – drainage visible on both the inner side and outer side of the dressing; drainage visible immediately after dressing removal and after wound cleansing; may continue throughout the treatment.

Copious – drainage not contained by a dressing deemed appropriate for the wound; drainage continues throughout the treatment requiring continuous cleansing, suctioning, or, in the case of bleeding. Pressure or thrombotic applications.

Using these definitions, dressing selection can be made based on the premise that the drier the wound, the wetter the dressing and the wetter the wound, the drier the dressing.  Thus, following are suggestions for managing each of the drainage amounts, keeping in mind that growth factors, collagen, or antimicrobial agents (silver, iodine, polyhexamethylene biguanides), can be delivered to the wound by any of the dressings when indicated:

Scant – hydrogels, transparent films, impregnated gauze (all are designed to moisten the wound bed by either adding moisture or by retaining the body’s own fluids in the wound bed, thus facilitating autolytic debridement); honey, cadexomer iodine in gel form

Minimal – thin foams and hydrocolloids

Moderate – thicker foams, calcium alginate, hydrofibers, nanofibrillar cellulose dressings

Heavy and copious drainage are best managed with 1) a combination of absorbent primary dressings and compression (in the lower extremity, unless contraindicated by diminished arterial flow) 2), pulsed lavage with suction, 3) negative pressure wound therapy, or 4) a combination of these therapies. 

Protection of the periwound skin with a moisture barrier or thin moisture resistant dressing (e.g. a thin hydrocolloid or foam) is essential to prevent maceration of the skin and further extension of the wound. Protection of viable structures within the wound bed (e.g. muscle, bone, and tendon) need the protection of moist dressings such as hydrogels and multiple layers of impregnated gauze to prevent dessication and further necrosis.  This is illustrated in the attached photo where hydrogel and layers of Vaseline gauze are placed over exposed bone in the infected amputation site, cadexomer iodine in the paste form is placed over exposed soft tissue to both kill the bacteria and help absorb drainage, additional foam is placed as a secondary dressing over the primary dressing, and a below knee amputation stump wrap is applied over all of the dressings.  Note also that more than one primary dressing is being used.  Wounds frequently have different types of tissue and different healing phases occurring at the same time and each tissue needs to have the appropriate dressing, therefore requiring more than one type of primary dressing.  Thus, the dressings in the BKA wound have multiple functions: protect the viable bone, decrease the bacteria load, manage the drainage, shape the distal stump for eventual prosthetic fitting, and allow the patient to be ambulatory with a walker. 

The selection of the dressing and how it is anchored will also depend upon the patient’s function.  For example, a bed-ridden patient with a heel ulcer may only need a foam dressing shaped specifically for the heel and anchored with a gauze roll, whereas an active, ambulatory patient may need a similar foam anchored with a gauze roll and self-adhesive bandage, as well as an adaptive shoe to prevent pressure during ambulation. 

Another category of biological dressings, termed cellular/tissue dressings, are used on clean granulated wounds in order to facilitate closure.  These dressings will be discussed next week as we address the last component of T/DIME – edges.

In summary, the factors to consider when selecting a dressing are wound healing phase, presence of bacteria, kind of tissue in the wound bed, size and depth of the wound, amount of drainage, and patient functional activities.  The wound is not a static entity, but a dynamic process that is ever-changing; therefore, the wound status requires assessment at every treatment session and up-dating of the dressing type in order to optimally facilitate the healing process.

Further in-depth discussion of wound dressings can be found at the following site:

Weir D, Brindle CT.  Wound dressings.  In Hamm R (Ed), Text and Atlas of Wound Diagnosis and Treatment: 2nd edition.  New York: McGraw Hill Education.  2019, 373-418.  Available at https://accessphysiotherapy.mhmedical.com/book.aspx?bookid=1334.  

Go to the profile of Rose Hamm

Rose Hamm

Physical Therapy, University of Southern California

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