This article aims to provide answers to many of the questions that users might ask. It is not intended to be the final word; rather the opposite. These answers are written to be a starting point and no more. Like every article in World Wide Wounds, it can be amended or extended following readers' suggestions and additions.
In the presence of wound exudate, hydrocolloids absorb liquid and form a gel, the properties of which are determined by the nature of the formulation. Some dressings form a cohesive gel, which is largely contained within the adhesive matrix; others form more mobile, less viscous gels which are not retained within the dressing structure.
In the intact state most hydrocolloids are impermeable to water vapour, but as the gelling process takes place, the dressing becomes progressively more permeable. The loss of water through the dressing in this way enhances the ability of the product to cope with exudate production [1].
One feature of hydrocolloids that is appreciated by clinicians is wet tack; unlike most dressings, they can adhere to a moist site as well as a dry one.
Reference 1: Thomas S., Loveless, P. A comparative
study of the properties of twelve hydrocolloid dressings. World
Wide Wounds, July 1997;
[Full Text:
http://www.worldwidewounds.com/1997/july/Thomas-Hydronet/hydronet.html]
Hydrocolloids provide effective occlusion; with dry wounds, they
can have a softening effect, and they have been used to prevent the
spread of MRSA (by providing a physical occlusive barrier). Reference: Thomas, S., Hydrocolloids Journal of Wound
Care 1992:1;2, 27-30 Reference 1: Thomas S., Loveless, P. A comparative
study of the properties of twelve hydrocolloid dressings. World
Wide Wounds, July 1997;
[Full Text:
/1997/july/Thomas-Hydronet/hydronet.html] Reference 2: Thomas S., Fear M., Humphreys J., Disley
L., Waring MJ. The effect of dressings on the production of exudate
from venous leg ulcers. WOUNDS 1996;8(5):145-150 One centre developed a two-layered cagelike dressing, the bottom
layer of which comprised a hydrocolloid pad, applied to the
surrounding healthy skin and covered by a fine chiffon or nylon
mesh. Liquefied necrotic tissue drained through the mesh and was
absorbed in a top layer of gauze, which was replaced periodically.
Thus it was possible to contain the maggots within the wound by
means of readily available materials. The study found significantly reduced itching, reduced pain and
increased pliability for both treatments, used over two months. The
authors concluded that hydration of the scar offered symptomatic
improvement, but no change in physical parameters. Few studies compare hydrocolloids with newer dressing types. In
one randomised controlled clinical study involving 100 patients
with leg ulcers and 99 patients with pressure sores in the
community, a 'hydropolymer' dressing and a hydrocolloid dressing
were compared. Statistically significant differences in favour of
the hydropolymer dressing were detected for dressing leakage and
odour production, but no statistically significant differences were
recorded in the number of patients with either leg ulcers or
pressure sores who healed in each treatment group. The future may see hydrocolloids used more selectively, but they
are by no means obsolete. When the efficacy of hydrocolloid occlusive dressing technique
is compared with conventional wet-to-dry gauze dressing technique,
the patient has been shown to benefit with a greater chance of
healing, faster healing times, and less pain. Nursing time is very significantly reduced, because the wound
does not need dressing so often (or for so long) dressing time is
markedly reduced. Costs are saved in materials alone, before even
considering the cost of professional time [1] Similar results have been found in patients with leg ulcers
[2] One prospective randomized trial compared parafin gauze and a
hydrocolloid dressing, applied on donor sites. The results showed
that the hydrocolloid is a less painful dressing than parafin
gauze, as well as achieving faster healing of skin graft donor
sites [1]. In another study, which involved patients with lacerations,
abrasions and minor operation incisions, compared a dressing with a
non-adherent dressing. While time to heal was similar for both
groups, patients using the hydrocolloid experienced less pain,
required less analgesia and were able to carry out their normal
daily activities including bathing or showering without affecting
the dressing or the wound. [2] The precise mechanism involved in the hydrocolloid ability to
reduce pain is not fully understood, but some possible explanations
have been discussed. [3] Yes There are many diffences in structure, flexibility, dimensions,
fluid handling properties and, probably, in other performance
parameters. The trouble is, few studies have compared different
brands [1]. Because of the shortage of in vitro research,
and a complete lack of (published) in vivo research,
manufacturers claims tend to be based on indirect comparisons such
as comparisons based on rival studies which compared hydrocolloids
and parafin gauze. One or two comparisons of 'patient satisfaction'
have been published, but these have no clinical value. Or indeed
any value at all, other than 'marketing exercises'. Reference 1 Thomas S., Loveless, P. A comparative study
of the properties of twelve hydrocolloid dressings. World Wide
Wounds, July 1997;
[Full Text:
/1997/july/Thomas-Hydronet/hydronet.html] A blinded study compared scanning normal superficial femoral
arteries with scans when one of five commonly used dressings were
applied to the skin above the artery, in random order. The blinded
operator graded the signal produced on a linear analogue scale. An absorbent material dressing and a bilaminate membrane
dressing did not transmit ultra-sound at all. Two thin membrane
dressings allowed excellent B-mode and colour flow images, in
addition to clear Doppler signals. A thin hydrocolloid allowed a
clear B-mode image of each artery to be visualised and an adequate
Doppler waveform to be obtained. However colour flow mapping was
less than optimal although it was possible in each of the
arteries. In patients who require dressings and who may require colour
flow duplex scanning of vessels in the same area, a product that
permits ultrasound transmission, thus saving the necessity of
removing the dressing for the assessment, clearly has
advantages Reference:
Whiteley M. S., Magee T. R., Harris R., Horrocks M., Eur J Vasc
Surg 1993 Nov;7(6):713-716 Burn wounds were followed until complete re-epithelialization
occurred. There were no statistical differences between the groups,
with respect to healing time, and patients' subjective responses to
treatment. However, dressing application (but not removal) was easier in
the hydrocolloid group. Furthermore, the that group had
significantly fewer dressing changes; a mean of three changes per
subject group compared with eight in the silver
sulphadiazine/chlorhexidine parafin gauze group. In this study,
both modalities were found to be equally suitable and effective for
small partial skin thickness burns. However, these wounds were necrotic; other clinicians firmly
recommend hydrocolloids, particularly for the protection of
diabetic wounds after the removal of necrotic tissue. [2] This issue has been controversial since the introduction of
hydrocolloids; currently, the best advice would seem to be "use
with caution in patients with diabetes." Reference 2:
Laing P., Diabetic foot ulcers. Am J Surg 1994
Jan;167(1A):31S-36S The results showed a mixed flora with prevalence of
Staphylococcus aureus. The average duration of the
treatment period was 67 days. The average interval between dressing
changes was 4.1 days. Subsequent bacterial cultures showed a
persistence of the original flora, but there was no correlation
between the type of flora present and clinical evidence of
infection or between the type of flora present and the rate of
healing of the ulcer [1]. In another study, the bacterial flora of chronic venous ulcers
treated with an occlusive hydrocolloid dressing were studied over
eight weeks. The flora was generally stable. Once a species was
present, it remained with the exception of Pseudomonas,
which appeared to be inhibited by the dressing. Twelve out of 20
ulcers contained anaerobic bacteria and healing did not appear to
be impaired by the presence of any particular species of bacteria
[2].
What are the main indications for
hydrocolloid dressings?
Hydrocolloids are easy to use, require changing only every 3-5
days, and do not cause trauma on removal. This makes them useful
for clean, granulating, superficial wounds, with low to medium
exudate.
Are there any side effects of hydrocolloid
dressings?
Contact dermatitis
Hydrocolloid wound dressings have been in use for some 20 years,
and have rarely been associated with allergic contact dermatitis.
However, some hydrocolloid dressings contain the pentaerythritol
ester of hydrogenated rosin as a tackifying agent, and this
substance retains the sensitizing potential of colophony.
How much fluid can hydrocolloid dressings
absorb?
The ability of hydrocolloids to absorb fluids varies considerably
over time, and between products. Laboratory studies [1] suggest
that the dressings may not be suitable for medium to high exuding
wounds. Other research [2] suggested that when properly applied,
the dressings might reduce the amount of exudate.
What is the role of hydrocolloid dressings in
maggot therapy?
Despite decades of experience in Maggot therapy, selecting
appropriate dressing materials continues to be a problem. The
dressing has to (1) prevent the maggots from escaping, (2) permit
oxygen to reach the maggots, (3) facilitate drainage, (4) allow
inspection of the wound, (5) require minimal maintenance, and (6)
be of low cost.
What is the role of hydrocolloids in
hypertrophic scars and keloids?
Silicone gel sheeting has been investigated for use in the
treatments of keloids and hypertrophic scars. Its mechanism of
action may be related to scar hydration. One randomized controlled
prospective study set out to evaluate a hydrocolloid occlusive
dressing that also acts by promoting a moist environment. Scar size
and volume, color, patient symptoms, and transcutaneous oxygen
measurements were taken.
Have hydrocolloids been rendered obsolete by
newer dressing types?
Over recent years, many new dressings have appeared on the market,
but few new dressing types. The continuing success of hydrocolloids
depends largely on their effectiveness as occlusive dressings. Any
new dressing has to match or better their performance and/or
compete on price. Currently, manufacturers of polyurethane foam
dressings are promoting them as an alternative to hydrocolloids.
Are hydrocolloid dressings cost
effective?
Studies too numerous to cite have established that hydrocolloid
dressings are more effective than 'traditional' dressings, such as
parafin gauze, dry gauze and saline soaks. Despite this, and the
relative reduction in cost over the decades, many health
professionals continue to use obsolete materials and methods.
Do hydrocolloid dressings reduce pain?
Pain is a feature of superficial wounds, such as skin graft donor
sites, particularly at dressing changes.
Is there any difference between
brands?
Is colour duplex imaging possible through
hydrocolloid dressings?
Colour flow duplex scanning is an accepted method of determining
the patency and haemodynamic status in infrainguinal grafts and
native arteries. There are often dressings covering the leg above
the vessel to be scanned.
How effective are hydrocolloid dressings for
partial thickness burns?
A study compared a hydrocolloid formulation with silver
sulphadiazine/chlorhexidine parafin gauze dressings in the
outpatient management of small partial skin thickness burns.
Are hydrocolloid dressings contraindicated
in diabetes?
An open randomized controlled study was carried out in 44 patients
with diabetes who had necrotic foot ulcers treated with or with an
adhesive occlusive hydrocolloid dressing. Fourteen of the 21
patients treated with adhesive zinc oxide tape had their necrotic
ulcers improved by at least 50%, compared to six out of 21 with the
hydrocolloid dressing (statistically significant). Fifteen patients
showed an increase in the area of necrosis during the course of the
5-week study and of these, 10 had been treated with the
hydrocolloid dressing. [1]
What are the effects of a hydrocolloid
dressing on bacterial growth?
Thirty patients with lower limb ulcers of different aetiologies
were treated with an occlusive hydrocolloid dressing twice a week
for a maximum period of 12 weeks. No antibacterial chemotherapy was
utilized. A culture was taken of the exudate of the ulcer before
commencement of treatment and weekly or bi-weekly thereafter.
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