Gels and gelling fiber dressings

Hydrocolloid dressings

The term hydrocolloids sounds somewhat intimidating and complex. Hydrocolloids are not that complicated. They are an occlusive type of dressing, which means they have negligible permeability - this type of dressing does not "breathe" a lot. They are often made of gelatine and polyurethane or gelatine and carboxymethylcellulose. Modern plasters against heel blisters are commonly made of this material, and the same technology is used in wound care. Stoma care products- for example, the plates for attaching stomal bags are commonly hydrocolloid.

 

Some hydrocolloid dressings are relatively stiff and are often referred to as hydrocolloid plates. They become softer and more flexible at body temperature, i.e., once placed on the skin. Hydrocolloid dressings have evolved quite a lot in the last few years. There are now thinner, more flexible types, and some are transparent. Some have alginates included for better absorption. Some hydrocolloids have a honey additive to provide some antibacterial properties. There are also hydrocolloid pastes that can be used as wound fillers.

We find that there are limited indications for this dressing today. In our opinion, there are two main areas where hydrocolloids can be very useful. One is to protect intact skin from mechanical forces. This may be shearing or pressure forces over bony prominences or other areas exposed to mechanical stress. Be aware that hydrocolloids are only a supplement to prevent skin damage - you will still have to ensure other off-loading practices are used. Hydrocolloids are also very useful to protect the skin from tubes and other medical applications, for example, in an intensive care unit. During the  Covid-19 pandemic, healthcare workers commonly used hydrocolloids to protect their skin from damage due to prolonged wear of face masks. 

The other area where hydrocolloids can be useful is to cover superficial skin abrasions and other superficial skin damage. The theory is that the hydrocolloid almost acts like a skin substitute, providing an adequately moist environment beneath the dressing while at the same time protecting the skin.  

When it comes to using hydrocolloids in deeper wounds, there is some controversy to this. Some caregivers routinely use hydrocolloids to treat deeper ulcers. They argue that hydrocolloids provide a perfect moist environment and aid the autolytic processes, thus speeding up the removal of dead tissue. We have seen that these dressings can work well in open wounds, and we have seen complications from using hydrocolloids. Bacteria can thrive well under these dressings with limited permeability, and we consider the risk of infection higher with this dressing group than with many other dressings. In our opinion, hydrocolloids give unpredictable results when using them on deeper wounds. Again, we know they can work well in experienced hands, but we think it is safer to use other products when you are not very experienced in wound care. 

In superficial wounds, hydrocolloids work as a primary dressing. In deeper wounds, you will need some sort of wound filler and then use the hydrocolloid over this as a secondary dressing. Most hydrocolloids can be cut into shapes. 

Many experts agree that hydrocolloids are contraindicated in diabetic foot ulcers. Never use them in pressure ulcer grade III or deeper, venous ulcers with a lot of exudate or ulcers with a suspicious smell. Using hydrocolloids in these patient groups asks for trouble with a very high risk of infection.

Most hydrocolloid dressings have some absorption properties, but not a lot. They do not perform well in wounds with much exudate. 

When using hydrocolloids, it is important that the plates adhere uniformly to the skin. A tip is to warm the plate in the palm of your hand for a few minutes so that it becomes softer and more elastic. Make sure that the skin area is free from lotion or creams. After applying the plate to the skin, lay your hand on it for another minute to better conform to the skin. When using hydrocolloids on intact skin, they can be left in place for seven days. If you use hydrocolloids in superficial skin damage, it is wise to change it a bit earlier, at least at the start to check that the skin is responding well. When using hydrocolloids in deeper wounds ( which we do not recommend), you should be vigilant and start with short dressing change intervals. 

Because hydrocolloids adhere quite firmly to the skin, they can cause skin damage upon removal of the dressing. Here it is also helpful to warm up the hydrocolloid plate using your hand and then remove it slowly without pulling too much. 

In summary, in our opinion, hydrocolloids are useful in the following settings.

  • as protection of skin areas subjected to shearing- or pressure forces

  • to protect skin areas from moisture ( i.e., stoma plates)

  • Category I pressure ulcers

  • Some Category 2 pressure ulcers

  • As a tool to make it easier to achieve an airtight seal when using negative pressure wound therapy in difficult anatomical areas like the groin, armpits, perineal area, and lower sacrum​

wa hydrocolloids.JPG

Figure 1  Almost every producer of wound care dressings also has hydrocolloid dressings in their portfolio. There are over 100 types of hydrocolloid dressings on the market. While many are quite similar, some are thinner and more flexible, and others may have additives like honey or alginate. There are also hydrocolloid pastes. 

Hydrogels

The name hydrogel literally means "water gel."  Hydrogel is made of water and gelling substances to give it a consistency of a gel. Often hydrogels contain propylene glycol and carboxymethylcellulose or another type of co-polymer. 

 

Hydrogels can be used in many types of wounds. Their primary function is to keep an optimal moisture level in the wound bed. Because the water is in gel form, the moisture is supplied to the wound in a way that it is not too wet and not too dry. Although hydrogels contain much water, they actually have some slight absorption capability. It is rarely wrong to apply hydrogel to a wound. However, in wounds with much exudate, it would be meaningless as the hydrogel is just washed out of the wound. 

Hydrogels always need a secondary dressing; otherwise, they will just run out of the wound.

Hydrogels have a cooling effect, and some patients may experience some pain relief when using hydrogels.

 

You can add other substances to hydrogels that may be beneficial to wound healing. Some add, for example, iodine ( 10%) to make an antibacterial hydrogel. This is mixed in a 50:50 ratio - that is, the iodine hydrogel ends up having a concentration of 5%. In our chapter on pain treatment, we refer to a method where we mix morphine and a hydrogel to provide topical pain relief for some patients. The basic recipe for this analgesic morphine gel is 10mg morphine ( for injections) mixed with 10ml hydrogel.

There are commercially available hydrogels with antimicrobial properties - Prontosan gel, for example, contains PHMB and betain. Some gels are hypertonic - i.e., have a higher concentration of salt. Others include vinegar or superoxidozed water to provide an antibacterial effect.

Summary of hydrogels:

Hydrogels are generally a safe choice as they can be used in many types of wounds. They work well in clean, granulating wounds but will also aid the autolytic process in wounds with necrotic tissue. However, in wounds with much exudate, they will not perform well and may even cause more maceration.

Several hydrogel products have antibacterial additives like PHMB, vinegar, super oxidized water, and salt. 

wa hydrogels.JPG

Figure 2 There are over 100 types of hydrogels available on the market. The image above only shows a small selection of these. Most hydrogels have very similar properties. Others have additives like PHMB, salt, or acetic acid to give them antimicrobial properties. 

Gelling fiber dressings: Hydrofiber dressings

Many generally call this product group for hydrofibres but be aware that the term "Hydrofiber" is a protected term that actually refers to only one producer's product range (Convatec). So if we are to be very correct, we should always mark the term Hydrofibre with the little R behind it to show that it is a registered trademark, i.e., Hydrofiber®.  To avoid these juridical complications, let us simply call these " gel-forming fiber dressings" or even simpler "fiber dressings."

There are basically two types of fiber dressings - one type ( Hydrofiber) is primarily based on cellulose, while the second is made of alginate ( a product commonly made of seaweed and behaves very similar to cellulose). When these products contact water, they quickly absorb this, and the dressing transforms into a gel. The resulting gel acts exactly like a hydrogel which we have discussed earlier. 

The absorptive abilities of fiber dressings and subsequent transformation make them a very versatile product group. They can be applied as a dry onto wounds with moderate exudation. If you have a wound that is on the dry side, you can pre-moisten a fiber dressing with, for example, saline and place this in the wound. 

There is some discussion about which type of fiber dressings are best - those based on cellulose or those based on alginates? Producers will show you tables where these products are compared concerning factors like absorbency, wet tensile strength, shrinkage, and so on. Producers of hydrofibers say that these absorb slightly better than alginates. Producers of alginates say that these have a better hemostatic effect. While we certainly do not doubt that there are some differences, in our opinion, most of these products perform well when used correctly. 

Convatec has focused its line of wound care dressings on its hydrofibre technology. Here you will find different dressings with respect to the amount of exudate in the wound. You will most likely have heard of Aquacel Ag dressings, Convatecs flagship dressings. These are silver impregnated hydrofibre dressings for antimicrobial effect. Convatec has spent considerable resources on research to show these products' efficacy, which is one of the reasons we highlight them here. Aquacel Ag and Aquacel Ag Burn have excellent documentation concerning treating burn injuries. Especially Aquacel Ag Burn differentiates itself from the crowd in that it can be left in place on a burn for up to three weeks. This has revolutionized the treatment of burns as we can save the patient from many unnecessary dressing changes. Aquacel Ag Burn previously also came in the shape of a glove, which was very practical for treating burns on hands. However, as far as we know, this product has been discontinued. Aquacel Ag + contains both silver and a surfactant; the latter has biofilm disrupting properties

wa hydrofibres.JPG

Figure 3  The term "Hydrofiber" is a patented trademark for Convatecs dressing technology. All their Aquacel products are based on this technology. They come in different variations with varying tensile strengths and absorptive properties. Those labeled with Ag contain silver as an antimicrobial. Aquacel Ag + also contains a surfactant. Competitors like Smith and Nephew have products with similar properties. 

Gelling fiber dressings: Alginates

As the name implies, alginates are based on cellulose-like substances derived from algae or seaweed. This appeals to most of us: the thought of seaweed gives wound healing a sort of natural aspect. However, in effect, alginates are very much the same thing as hydrofibers, although most producers will disagree here with us. Let us, therefore, rephrase the sentence: hydrofbers and alginates behave very similarly. They both absorb wound exudate and become gel-like in the process. They exist in different variations according to absorption properties, tensile strength, and whether they have additives like silver. As we mentioned earlier, it is postulated that alginates are better at stopping minor bleeding in the wound ( for example, after a debridement) while hydrofibers have slightly better absorption. In everyday clinical practice, these differences are not so significant. 

In summary: Alginates are often used as wound fillers for deeper wounds with a fair amount of exudate. Alginates with silver are used in wounds with a higher bacterial burden. While hydrofibers with silver have the best documentation for burn wounds, it is expected that alginates with silver can perform similarly in treating burns. 

 

 

wa alginates.JPG

Figure 3 Since Aquacel and the Hydrofiber trademark dominate the Hydrofiber market, most other companies focus on alginate dressings instead.  These have very similar properties to Hydrofiber dressings and are also found without and with silver additives.  The alginates containing silver are usually marked with Ag.  The image above shows only a small selection of alginates on the market today.