Introduction
Wounds are generally classified by their visual appearance as necrotic, sloughy, granulating or epithelializing, each with different dressing requirements. All wounds may become infected at any stage of the healing process and develop an unpleasant odour. This means dressings may also need to have antibacterial activity and/or be deodorising. The overall aim in the choice of dressing is to provide an environment at the surface of the wound in which healing can occur (28). The dressing may be required to maintain or provide a moist environment, absorb excess exudate, promote autolytic debridement (process of natural wound cleaning), provide thermal insulation, relieve pain and protect the wound from trauma. To encourage patient compliance, dressings should require infrequent changing and be available in various forms (28).
Exudate is beneficial to normal wound healing as it contains growth factors that promote the growth and migration of fibroblasts, endothelial cells and keratinocytes. However, some chronic wounds produce excess exudate that may macerate the surrounding skin and delay healing. These wounds require dressings that absorb exudate and, if they require frequent changing, should be easy to remove with no tissue trauma or pain.
There is no single dressing suitable for all types of wounds and often a range of different dressing types is used during the healing of a single wound (28).
A primary dressing directly contacts the wound and the secondary dressing is placed over the primary dressing. The central absorbent portion of a composite is called the island dressing. Some dressings need a bandage or some form of adhesive layer to keep them in position, whilst in others there is an adhesive layer incorporated. Non-adhesive dressings such as gels cause less pain and trauma on removal as they can be washed out of the wound (28).
HISTORICAL BACKGROUND OF WOUND MANAGEMENT
The history of wound healing is almost like the history of humankind. One of the oldest medical manuscripts known to man is a clay tablet that dates back to 2200 BC. This tablet describes the “three healing gestures”—washing the wounds, making the plasters, and bandaging the wound (41).
What the ancients and early moderns referred to as plasters is the present-day equivalent of wound dressings. These plasters were mixtures of substances including mud or clay, plants, and herbs. Plasters were applied to wounds to provide protection and absorb exudate. One common ingredient used in plasters was oil, which may have provided some protection from infection as bacteria grow poorly in oil, and oil would have prevented the bandage from sticking to the wound. One of the interesting earliest known wound care products was beer. The Sumerians brewed at least 19 different types of beer. An interesting prescription for wound healing described in Mesopotamian culture stated, “Pound together fur-turpentine, pine-turpentine, tamarisk, daisy, flour of inninnu strain; mix in milk and beer in a small copper pan; spread on skin; bind on him, and he shall recover” (41).
The Egyptians may have been the first people to use adhesive bandages and were most certainly the first people to apply honey to wounds. Honey, grease and lint were the main components of the most common plaster used by Egyptians. Lint made from vegetable fiber probably aided drainage of the wound; grease and honey may have prevented infection. Grease made from animal fat may have provided a barrier to bacteria. While honey appears to be an effective antibacterial agent, it has many other healing properties. Honey has been used for thousands of years and is still part of some advanced wound dressings. Honey was also used for wound care in India long before Christ, demonstrating that separate medical cultures empirically arrived at the same successful therapy.
Egyptians painted wounds with green paint containing copper, which is toxic to bacteria. When we think of ancient Egypt, we think of pyramids and mummies. The art of wrapping the bodies of the dead probably influenced the bandaging of wounds. Also the art of preventing decomposition by embalming may have contributed to early advances in controlling infection (41).
The Greeks stressed the importance of cleanliness. They recommended washing the wound with clean, boiled water, vinegar and wine, and differentiated between “fresh,” or acute, and non-healing, or chronic wounds. An interesting excerpt from the Hippocratic collection about wound healing is, “For an obstinate ulcer, sweet wine and a lot of patience should be enough.” An early description of the “four cardinal signs of inflammation”—rubor, tumor, calor, et dolor (redness, swelling, heat, and pain)—came from the Romans. In the 19th century, the antiseptic technique was a major breakthrough. Introduction of antibiotics helped control infections and decrease mortality (41).
In the 20th century came modern wound healing. Presently, there are more than 8,400 wound care products. Most modern dressings contain highly absorbent materials, e.g. alginates or foam. There are occlusive and semi-occlusive dressings, growth factors, advanced honey-based dressings, bioengineered tissue and negative pressure therapy, all of which have changed the way chronic wounds are currently treated.
In summary, the first wound treatments were described 5 millennia ago. Since then, various principles of wound care have been passed on through generations. In contrast to large numbers of general technological inventions over the past 100 years, progress beyond ancient wound care practices is a recent phenomenon (41).
Role Of Wound Dressings and Complications
Occasionally, healing may not be the primary aim of a wound dressing. An example of this is a palliative patient with fungating cancer of the skin in which the intention of the wound dressing is to aid symptom control and aesthetics. A physiological wound environment is attained by a dressing when the wound is kept wound moist, absorbs excess exudate, provide thermal insulation, eliminate dead space, avoid trauma/pain on dressing change, minimise scar tissue formation, minimal toxicity to surrounding skin and base, non-viable tissue debridement and maintain gas exchange (6).
Maintaining a temperature similar to that of the normal body allows optimal cellular function. Hypothermia causes a relative vasoconstriction leading to a reduction in oxygen delivery to phagocytes, which reduces mitotic activity and growth factors. The insulation provided by occlusive dressings can overcome these issues, however complications arise. Maceration of the skin occurs when a wound is kept overly moist or when exudate levels are high. One of the properties of a dressing is moisture vaporization. Dry wounds require dressings with a low vaporization rate, and exuding wounds the opposite. When the balance is not right, an overly moist wound can cause skin breakdown, delayed healing and a raised bacterial count (6).
Another common complication of wound dressings is a surgical site infection, affecting at least 5% of patients undergoing surgery. Clinical factors are the type of surgery, length of surgery, patient’s physiological status, appropriate hair removal and wound dressing to name a few. Evidence has shown that practices such as antiseptic hand and skin preparations, antibiotic prophylaxis and showering reduce the incidence of such infections (6).
Desirable Properties of a Wound Dressing Material
The ideal dressing should be: non-adherent, impermeable to bacteria, capable of maintaining a high humidity whilst removing exudate, thermally insulating, non-toxic or allergenic, comfortable and conformable, be able to shield from further trauma, infrequently changed, cost-effective, non-scarring, possess a long shelf-life and easily available in community and hospital settings. All these points will lead to increased chances of patient compliance and better wound healing (8).
The economics of wound management can be complex, as newer dressings have relatively high unit costs but require changing less frequently than traditional dressings. They can therefore be more cost-effective and convenient for patients (42).
