Understanding Topical Silver Treatment in Wound Care
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This is Kathleen Satterfield, DPM
Clinical Associate Professor
Department of Orthopedics/Podiatry Service
University of Texas Health Science Center at San Antonio
We are going to discuss 4 main topics today, first of all:
1. The history of silver use in medicine.
2. Also the modern uses of silver.
3. The evolution of silver products for medical use.
4. The evidence: The pros and cons.
The use of silver in medicine and other areas of health is really nothing new. Archeologists have found evidence that people used it in ancient Rome and ancient Greece primarily to prevent spoilage and bacteria from forming in water jugs that concept even made it to the new world where pioneers often used silver dollars in their barrels of water to prevent bacteria from growing.
Up until the 19th Century in Germany silver had been primarily used as a disinfectant. But at that time an obstetrician started to use 1% silver nitrate solution in eye drops in newborns. There had been a long history of blindness in newborns caused by postpartum infections. This practice started by Dr. Crede in 1834 virtually eliminated blindness due to this cause.
At the time of World War II several antibiotics began to be commonly developed and used and silver use dropped off dramatically as the medical profession and the patientâs clammered towards the use of antibiotics for infections.
Probably the most recognizable early modern use of silver in medical setting was silver sulfadiazine or what is commonly known as Silvadene. This unique early use featured a silver cation and a sulfadiazine mixture in an easily soluble cream and by virtue of this combination both were still active. This allowed many antimicrobial properties against gram positive, gram negatives, and also fungus. The greatest use of this was for the burn patient and it was used extensively as a lifesaving measure often in this population. It did have a limited penetration depth when placed on a wound and that always had to be kept in mind. Also practitioners soon learned that use of this product could actually increase exudates and that was not always a good thing for the wound.
Silver nitrate continued to be a major player that was easy to use. It was very inexpensive. The chemistry behind it is that a silver ion precipitates out forming an insoluble salts. This as we all know will discolor tissue and cause a caustic burning injury to tissue at high strength. We have of course used that to our advantage to help stem bleeding and those antimicrobial properties still exist gram positive, gram negative, and as well as fungus.
It is an interesting progression that silver was used in Ancient Rome and Greece and then it came to America. Pioneers used it going across the country in covered wagons and now scientists are using it in space shuttle in water purification systems. This system is taking wastewater from the fuel cells and reprocessing it through silver and this has eliminated the need for caustic chlorine systems on board the shuttle.
We know it works but how exactly does it do that. Well probably the most important thing that silver dose is on the surface of the wound, it decreases matrix metalloproteinase and their activities. In doing that we get 3 main responses. We increase surface calcium. We enhance anti-microbial effects and by doing both of those things, we help to decrease inflammation.
The destructive matrix metalloproteinases, primarily the gelatinases have some very negative effects on a wound and in the diabetic, we know now that their singling processes are affected by their disease and so the wound environment may have way too much of these products sitting on the wound at anyway 1 time where as these MMPs are useful at certain time in the history of the wound, they are not needed all the time but that singling process is off in the diabetic patient. Let me give you an example, you have a patient who has an eschar and that eschar needs to be sloughed away, well the gelatinases will come up underneath that and loosen it but if you have got a fresh diabetic ulcer and you are trying to grow new tissue across that you do not want a gelatinase there because what is it doing. It is denaturing the growth factors, it is degrading the new tissue, it is degrading collagen and Elastin and that is going to be very destructive to the wound.
The overall effect is going to be that you have a wound that either would not heal or has very delayed healing.
It is interesting that such a simple element such as silver has really no significant resistance developed yet with every other antibiotic out there available to us developing resistant bacteria right and left. It is interesting that we can still turn to silver at least so far and find then and find that it is active against most of the bacteria and fungal agents that we encounter. So why is this, it is because the mechanism of activity is that it blocks the cell respiration pathway of bacteria and by doing this it shuts down the bacterial growth.
We are bombarded these days with advertisements and detail representatives and presentations about silver and it makes you wonder is it all the same, well no. There are big differences.
Let us look it three common products first of all the silver nitrate 0.5% solution, silver sulfadiazine, and Acticoat. Now the real difference between these is in the last column there and that is in the release. With silver nitrate solution you are getting in immediate release of its full strength, so whatever that strength is in this case it is very strong. You are putting that directly on the tissue. It is going to have those anti-microbial effects that you are hoping for but also what is it going to be doing to those skin cells to the potential angiogenesis in that fragile wound that may not be what you need at that point in that woundâs life. With the sliver sulfadiazine, we are getting a slower release, remember this comes in the soluble cream vehicle and so that is released over 12 to 24 hours period before it is basically neutralized. Then you go to something like an Acticoat product where this is within dressing and the release is very extended. The silver ions are released over period of 48 plus hours and so this also has a much lower concentration of silver ion in it and so that lower level is released slowly on the wound and so we are not getting the negative effects that can occur with hyper-saturation of a wound with silver ion.
As the scientific community begin to realize that hyper-saturation in silver ion on a wound was not a good thing, we started to see the development of more and more products that would release the silver ion either slowly or in lesser concentrations thus preventing the devastating effects to the wound. One of the more common once is PRISMA matrix, which has a 1% silver product in it in a collagen base and it also contains a cellulose component. By virtue of this matrix it is protective to the wound and allows for a sequential release of the silver ion.
Adventure to say that Acticoat is probably one of the most well known products containing silver. It was a very early player in the wound care world and easy to use. It found great favor. It is composed of a 3-ply gauze dressing and the inner core is an absorbent layer of rayon and polyester. The outer layers of the product are silver coated high-density polyethylene mesh. This silver coating is actually formed out of porous nanocrystals that organized into coarsely formed columns and by virtue of this form, it has more surface to interact with the wound and with _______ potential microbes.
There is one common mistake that is made with Acticoat, however, and I admit that I made it a few times myself early on and that is when placing it on the wound and knowing that it needs to be moistened reaching for the bottle of sterile saline rather than sterile water and the saline solution would react with the silver ions and make it not as effective and so it is important to wet the product with sterile water and not a saline solution.
You will note that this reference is from the burn care literature and it is important to note that much of the literature about silver products in medicine is indeed from burn care literature. They really have made the most inroads in that field in reference to using silver as an anti-microbial and anti-fungal agent with very little resistance. This particular study they noted that the rate and percent of microbial killing is enhanced if you have a nanocrystalline silver release and remember that is what Acticoat provides in those irregularly formed columns. When we moisten the product with water, again not saline, that actually is releasing silver radicals and when those silver radicals are released then that they can interact with the microbes and it becomes a very active product.
The product Arglaes really made some strides when it was developed because it came in several forms, realizing that no wound is the same and the fact that it came available as a powder and a film and a dressing, really made it so valuable to the wound care world. The thing that to get one step further though was the fact that it could be active up to seven days and this was a great feature for those wounds that were not actively infected but would benefit from an anti-microbial at the wound surface to prevent potential infection but that would also benefit from not being uncovered daily and exposing them to potential nosocomial infections or to being dehydrated. This was an advancement.
Silverlon is another product that I do not believe was as widely noted in the literature or in use but that I personally prefer greatly. This is a product that can actually be removed from a wound, washed in clean water, and then returned back to the wound. It is also on a flexible fabric. The notes that it 3-dimensional meaning because it is a woven fabric and has an elasticity to it, you can stretch it thereby allowing interaction of the wound or the wound fluids with all the surfaces available and all of those can give off the silver ion. The patients liked it. It was not a painful product to remove from the wound nor were the other to that I had just described but it was a popular product in our wound care clinic.
You can see a theme developing in products as we progress through these. With SilverCel again we are seeing release of elemental silver. It is sustained over the life of the product. Another thing that you will see as a trend in products as you do here that is conformable to the wound because no two wounds are alike. They are very irregular, sometimes very difficult to dress as we all know. This one incorporate silver coated nylon fibers. It is not woven. It is a pressed pad and it comes in contact with the wound.
I think we all are aware of how important it is to maintain moisture at a wound surface and yet not allow exudate to buildup there. It is a fine line. The SilvaSorb dressing certainly help us to maintain that line. It has scaffolding of what they call a MicroLattice and it allows the ionic silver to be suspended in that until some moisture from the wound comes up into that Lattice and triggers its release and then the underlying dressing can absorb any additional exudate up to 5 or 6 times its weight, so it has a fairly long lasting effect on the wound as it releases the ionic silver.
We can pick up a medical journal or go to a presentation without hearing the words evidence-based medicine in these days and this probably a very good thing. David _______ and his group really coined this term in modern times and it is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients. The practice of evidence-based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research. That does not mean that we unplug our clinical sense and look only to studies but what it says that we can combine the two and what _______ and the people at places like _______ collaboration are looking to are really the goal standard studies. The randomized controlled trials, they give us the best answers.
So it is important not only to realize what EBM, evidence-based medicine, is but it is important also to realize what is it not and probably the biggest complaint about it is people will say that is just cookbook medicine. That is just telling me take step I, step II, and then step III but it really is not it cookbook medicine because it takes into the consideration clinical experience as well. It is not cost cutting medicine either and some people have criticized it saying well companies, insurance companies third party payers want me to go to use of EBM because it will cut down on expenses. That is not the truth, it often will drive up some cost in the short-term. It may require you to order more tests, may require you to use more expensive product. Over the long run we would hope that we would give us the best answers for individual patients in a more effective and efficient way but sometimes the road map to getting there maybe an expensive one and thirdly it is not just limited to those RCTs or randomized controlled trials. In a perfect world, we would have RCTs for everything but we all know that is not the case. There are a lot of health issues out there that they do not have randomized controlled trials to guide us yet.
Well I mentioned the Cochrane collaboration earlier and so when we turned to them and asked them what do they have? What kind of evidence do they have right now on silver? This is what they will tell us and this is a fairly new ruling by them. I say ruling but what they call it is a review. They will assign a topic to a group that has expertise in an area and in this case they assigned the topic: Silver based wound dressing and topical agents for treating diabetic foot ulcers and the group that was assigned this looked at randomized controlled trials and/or non-randomized controlled clinical trials and the patients with type-1 or type-2 diabetes and related foot ulcers. There are probably some of you out there already saying hhhhhhh.
Well they raise the stakes even higher. They also put their selection criteria for this review that they wanted to be able to compare the silver product with sham or placebo dressing and alternative non-silver dressing or no dressing, and they wanted to be able to base their outcomes on healing rates or infection. That is a tough order.
Anybody in the wound care world probably would not find this surprising then that they concluded that despite widespread use, there are no randomized trials or controlled clinical trials existing for diabetic foot and the use of silver. Trials are needed to determine clinical and cost effectiveness and long-term outcomes including adverse affects. Does this means that silver does not work on a diabetic foot ulcer, well of course not. We know from our experiences that these products do work on these types of wounds. The thing that it says though we do not have the best case evidence yet. It also puts up a challenge to perform those studies. They are needed.
Remember how I said earlier that we do not have to have those RCTs. We take what we got and we evaluate that and we do have some fairly good scientific evidence, although, I did not meet the level of Cochrane collaboration, which is deniably be highest and difficult to obtain but we have this a study that was a comparative evaluation of antimicrobial activity of Acticoat, antimicrobial barrier dressing, and again this was looking at the burn literature. They compared Acticoat against silver nitrate, silver sulfadiazine and Acticoat and they found that in that comparison Acticoat had the lowest MIC. It had the best antimicrobial performance of those and it was killing the bacteria at a much faster rate and thereby putting the patient at much less risk.
Again turning to the burn literature, we found another study about the safety of Acticoat and perhaps the fact that we find all of these studies with Acticoat is a reason why this is one of the most used products. They have gone to the trouble to do these studies. In this study, they had a matched the pair, randomized study evaluating the efficacy and safety of Acticoat, silver coated dressing for the treatment of burn wounds and the patients were randomized in the study to either 0.5% silver nitrate solution or the Acticoat and the patients who had the Acticoat arm of the study reported less pain with their wounds. The providers of the care reported no difference between the ease of use of the two products and then overall they found less sepsis in the Acticoat treated wounds.
Once again to the burn literature and again looking at Acticoat, this is a more recent study reported in 2005. This was a prospective randomized trial of Acticoat versus silver sulfadiazine in the treatment of partial-thickness burns; which method is less painful. They found the same outcomes as had earlier been found; less painful and increased antimicrobial effects.
Finally in 2005, in the journal of wound care, there was a report regarding chronic wounds with signs of local infection. In this evaluation of silver releasing hydroalginate dressings the authors reported that the use of these were valuable but that they may positively influence the wounds prognosis and that they were well tolerated. I would not call this a resounding support for silver dressings but it certainly was a step in the right direction and it simply tells us that if this is the best evidence then we certainly need to generate some evidence ourselves regarding the use of silver dressings in difficult wounds.
Again in the journal of wound care in 2004, we see another study that showed the use of silver releasing dressings may have a clinically favorable influence on prognosis. This was reviewing the effects of activated charcoal silver dressing on chronic wounds with no clinical signs of infection. Kind of holding their own, again if this is the best evidence that we have in the wound care world, it certainly presents us with the challenge that we need to generate some better evidence.
In 1998, the infection control community had already thrown down that gauntlet by saying that there was a role for topical silver treatment not only for a therapeutic agent but also probably is a prophylactic agent to prevent microbial growth and infection and they were seeing much more antibiotic resistance strains and felt that there was a need for more research in this area.
This is an illustration of a patient in our University of Texas Clinic who had a very slow-to-heal wound with infection and tunneling. The tunneling was from the large ulcer seen at the heel to that seen above at the ankle. This really created what we often call the stunted wound.
This is the type of wound that we would treat from several different directions at the same time, and I just like to say about that the sometime practitioners are uncomfortable about combining therapies, and I say that it is sometimes the best things in the world to do for the patient. There is rarely one tool that fits all needs in one job. There is infection to control. There is Bioburden. There is Biofilm. There is moisture need. In this particular case, this patient had an Apligraf applied and then an Acticoat was placed over this and order to control any Bioburden and allow some healing to take place.
Shortly after, the tunneling is no longer present. The Biofilm has been removed. The wound is starting to fill in. There is some angiogenesis present. The borders are active now. This is a wound that has potential for healing. Another Apligraf would place on at this time and for continuing protection another Acticoat. This is an interesting and very affective combination of tools.
Depending on who you read these days. You will hear that silver is going to kill a wound or will make it heal. I am somewhere in the middle but is silver toxicity truly a fact or is in a myth.
There is certainly some fact to it. In fact you can have systemic toxicity of silver. This was much more common in days when you utensils and drinking vessels were made more of silver. People would develop what was called Algeria and it was often described as the look of the living dead and what do I mean by that. Well the patientâs face would have a very grey cast to it. They truly did not look like they had any healthy complexion whatsoever. They truly looked like the living dead. Now if you have a local toxicity and anybody who used silver nitrate on a bleed or on a wound will notice that they can get some staining of the skin. This is just staining of the skin. This is not a systemic toxicity or an Algeria. What they are getting locally is there they are getting some cell necrosis and it is going to affect the fibroblast in that area.
Once you chose to use a silver product on your difficult wound, it is important to do several things. You need to reassess on a regular basis. Very important to look at that wound and to adjust your treatment. Do not be shy about combining therapies that you do not have to pure use of one to completion. Combine the positive effects of the several therapies to the benefit for your patient. I think the thing that probably seeks more wound than anything is exudate. You have got to meet the demands of the exudate and then just do not dig yourself into a hole and say I not changing. If the wound starts the change and the therapy
is no longer meeting the need, change. Assess what the problem is for the wound at that time and pick the best tool for the job. Do not be resistant to change.
Thank you for your patience and your attention. It has been a pleasure lecturing to you.
|Goals and Objectives|
After participating in this activity, the viewer should be better able to:
1. Understand the historical use of silver in medicine.
2. Appreciate the different types and available prescriptions using silver.
3. Discuss specific methods of use of the various silver products.
4. Appreciate the results of the Cochrane Collaboration on Silver.
5. Appreciate the best current clinical evidence regarding silver use in wound care.
Estimated time to complete this activity is 43 minutes.
Physicians, diabetes educators, and other health care professionals who treat patients with diabetes.
Complete the 4 steps to earn CE/CME credit:
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