Wound Healing – ‘Improving’ on Mother Nature
Doctors believe they need to assist the body’s natural repair mechanisms when treating wounds. But evidence shows that many antiseptics and dressings may do more harm than good.
Cuts, grazes, wounds, and lacerations – to varying degrees, we have all had to deal with them at one time or another. If you are admitted into hospital for surgery – even the minimally invasive variety – you also have the problem of how best to help a wound heal.
Your skin is your body’s biggest organ and plays a large role in keeping you healthy, regulating body temperature and acting as a barrier to keep body fluids in and bacteria out.
Given the optimal conditions, the human body is remarkably efficient at repairing injuries to this barrier. When the skin is cut, complex biochemical reactions are instigated. These include the activation and/or destruction of cellular and molecular elements such as white blood cells, red blood cells, endothelial cells and blood platelets – all part of the initial inflammatory process.
Inflammation, far from being undesirable, is what protects the site from further injury while it begins the process of tissue repair. Yet, for years, as with so many areas of medicine, we have tried to beat Nature at her own game by applying sutures, harsh antiseptics and lots of dry, absorbent bandages to ‘help’ wounds heal better. Many of these practices in wound management have been put to the scientific test in recent years – and many of them have proven to be more destructive than helpful. Doctors from a wide range of specialities now admit that the process of wound care is based largely on habit and anecdote rather than science.
For instance, even though the body is well equipped to fight off invading bacteria, wounds have been swabbed with alcohol, antibiotics, iodine, Mercurochrome (merbromin), merthiolate, hydrogen peroxide and other medications to keep them ‘clean’. Today, antiseptics such as hydrogen peroxide, povidone iodine, acetic acid, chlorhexadine, cetrimide and Dakin’s solution (sodium hypochlorite) are all part of the physician’s antimicrobial arsenal.
Unfortunately, many of these strong antiseptics can also interfere with the body’s own healing mechanisms. In fact, cleaning a wound is often the first hurdle at which doctors fail their patients, since antiseptic solutions can interfere with the process of wound healing in several important ways.
All wounds need to be cleaned before they can be assessed and treated. Serious wounds – for instance, those resulting from a car crash – may be dirty and potentially more liable to infection and, thus, require careful cleaning.
Such wounds may occasionally justify the use of antiseptic washes. The problem is that antiseptics don’t just kill germs; they also kill beneficial leucocytes – the body’s own bacteria-killing cells – as well as fibroblasts, the cells that eventually form new skin (Drug Ther Bull, 1991; 29: 97-100; J Burn Care Rehabil, 1991; 12: 420-4).
The current thinking is that all but the worst types of wounds can be safely and effectively washed with a simple saline solution that is not cytotoxic (deadly to cells). In addition, very dirty wounds can be cleaned with water pressure. In hospital, staff may have access to special equipment but, at home, running water or using a showerhead may be just as effective.
Benefits of moisture
The next question is how best to bandage and maintain the wound during the healing process. For years, the standard advice has been to keep the wound site clean and dry. While no one would argue over the benefits of keeping a wound clean, keeping it dry, usually with a gauze bandage that allows air to get to the site, and allowing a scab to form can actually slow the healing process and is more likely to produce a scar.
Thinking on wound healing began to change in the 1960s when George Winter, PhD, then a student at the University of London, performed a series of experiments in wound healing on animals.
Winter was asking some basic questions – like whether allowing a wound to dry out was the best way to achieve optimal healing. On comparing wounds that were either kept moist with a polymer film or left to dry out, Winter found that, on examination with a microscope, the wounds that were kept moist healed twice as quickly as those allowed to dry out (Nature, 1962; 193: 293).
Not long after Winter had reported on his findings, a human study also found that keeping wounds moist was much more effective than allowing them to dry out (Nature, 1963; 200: 377). Subsequent studies also found that wounds – both superficial and surgical – that are kept moist with, for instance, one of the newer hydrocolloidal dressings, healed faster (J Surg Res, 1983; 35: 142-8; J Invest Dermatol, 1988; 91: 434-9; J Enterostom Nurs, 1993; 20: 68-72).
Gradually, the idea of moist healing evolved and gauze-based bandages have, in some hospitals, been replaced by a range of natural and synthetic materials that effectively maintain the moisture balance at the wound site.
Although often referred to as ‘occlusive’ dressings, this description is not quite accurate since occlusive implies that they prevent the exchange of gases or liquids. Such bandages are really ‘semi-occlusive’ inasmuch as they seal off the wound site, but also allow the transmission of oxygen, nitrogen and water vapour.
Many factors make moist dressings the optimal way to heal wounds. Perhaps most important of all, they provide an ideal environment for cells to stay alive and replicate. The natural environment of the cell is moist. Dry cells, such as hair and nails, are dead cells that are incapable of reproducing at their point of origin. The body, too, is largely an aqueous organism. However, the outer layer of the skin, the stratum corneum, is less watery. Its cells are filled with keratin, which provides a barrier to water loss through the skin.
A wound is a break in this protective barrier that allows moisture to escape from the underlying moist tissue and causes the death of the superficial cells, a process that results in the familiar scab, composed largely of dried blood and other fluids.
While traditional thinking is that the scab is Nature’s own barrier to moisture loss, newer thinking views the scab as inefficient.
Scabs also prevent new cells from colonising the wound area. When a scab is allowed to form, epidermal cells have to penetrate deeper into the dermis, where the environment is moist, before they can proliferate. This means that the wound will only heal from the bottom up whereas, in a moist environment, the wound will heal from the sides and bottom simultaneously.
Newer-type dressings such as polymer films and foams, hydrocolloids, hydrogels and calcium alginates allow much less moisture evaporation, allowing the cells responsible for the filling in and resurfacing of the wound to remain in an environment in which they can live and replicate.
Moist dressings may also act as insulation, helping to maintain the optimal temperature of the skin. Left open to the air, the evaporating moisture has the effect of cooling the wound area. This tissue cooling is thought to be one of the factors that leads to an increased risk of infection. The cooler temperature at the wound site reduces the amount of oxygen available to infection-fighting cells such as neutrophils – which use the chemical byproducts of oxygen metabolism to kill invading bacteria. The process of cell replication may also slow down at lower temperatures.
Less infection
Perhaps the most important aspect of moist dressings is that they are many times more effective than dry dressings in preventing infections. This is as important an aspect of healing to the child in the playground as it is to the patient in hospital, where opportunistic antibiotic-resistant bacteria can so easily enter a wound site.
In this respect, moist healing is something of a paradox. Indeed, one of the concerns voiced in response to George Winter’s earlier conclusions was that a moist environment would be a breeding ground for germs.
This point of view, however, failed to acknowledge how efficient the body is at fighting infection on its own when it is properly supported. This attitude also didn’t recognise that a wound colonised by bacteria is not necessarily at risk of infection. All wounds, no matter how carefully cleaned, are colonised by bacteria.
The problem arises when bacteria are given the opportunity to multiply. In a properly nourished and supported body, natural infection-fighting mechanisms can easily keep bacteria in check.
The copious amount of data that has been amassed on this subject concludes that moist healing does not increase infection rates but, instead, appears to decrease them (Wounds, 1989; 1: 123-33; Hutchinson JJ, A prospective clinical trial of wound dressings to investigate the rate of infection under occlusion, in Proceedings: Advances in Wound Management, London: Macmillan, 1993: 93-6).
This appears to be in part because the newer-style dressings present an effective physical barrier to bacteria that cannot be achieved with traditional gauze bandages while, at the same time, ensuring the optimal function of the body’s infection-fighting cells (Am J Surg, 1994; 167 [Suppl]: 21S-4S; J Am Acad Dermatol, 1985; 12: 662-8).
This was evidenced by the fact that, in one study, the infection rate of wounds treated with a conventional method was 7 per cent compared with 2 per cent using a moist, hydrocolloidal dressing (Am J Infect Control, 1990; 18: 257-68). In another study, bacteria were found to be capable of penetrating 64 layers of gauze, but were incapable of penetrating a single layer of polymer film (Am J Surg, 1994; 167: 21S-4S).
Other theories include the idea that a moist dressing helps maintain the slightly acidic pH of the skin (Am J Surg, 1994; 167: 2S-6S). This, too, may inhibit certain types of bacteria, such as Staphylococcus aureus and Pseudomonas aeruginosa.
Patients also report less pain when wounds are kept moist. Newer-style dressings are thought to protect nerve endings from the environment and keep them moist, thus reducing the perception of pain. With gauze dressings, nerve endings may become damaged during dressing changes. Numerous studies involving people from all walks of life and all occupations, including football players and industrial workers, attest to the fact that patients treated with hydrocolloidal dressings experience less pain (Arch Dermatol, 1991; 127: 679-83; Athl Train JNATA, 1988; 23: 341-6; Military Med, 1988; 153: 188-90; Int J Sports Med, 1991; 12: 581-4).
Another intriguing possibility as regards the effectiveness of moist dressings is that they help to maintain the electrical integrity of the wound site. By keeping the site moist, it allows the body’s own electrical current to flow more or less uninterrupted. It has been demonstrated that the electrical charge of wound tissue is positive in relation to the surrounding intact skin (Clin Dermatol, 1984; 2: 34-44). This positive current is thought to orchestrate the migration of healing cells to the site, but this current cannot flow if the skin is dry. Such information provides a context for studies into electroacupuncture and the successful healing of a variety of wounds, even those that had failed to heal with prior conventional therapy (Am J Acupunct, 1999; 27: 5-14; Minerva Med, 1980; 71: 3709-13).
For this and other reasons, moist dressings may also have aesthetic benefits for patients. Studies show that they can help lessen the appearance of scars (Arch Dermatol, 1991; 127: 1679-83).
When wounds won’t heal
Clean cuts can heal remarkably quickly and well with a minimum of intervention. But some kinds of wounds simply don’t heal. The reasons are manifold. The patient may have an underlying health problem, such as diabetes or venous insufficiency, that interferes with the healing process.
Burns, crush injuries and other extreme traumas may also prove difficult to heal over the longer term. In such individuals, wounds can become chronic and suppurating, and prone to infection. Doctors may treat these with systemic antibiotics – even though these are unlikely to be effective at the local level (Austr Prescr, 1996; 19: 11-2).
Steroids, too, impede the proliferation of fibroblasts and collagen synthesis, and the application of antiseptics, as has already been explained, is unlikely to help chronic wounds, since it only serves to kill the very cells that are necessary for repairing the damage.
In searching for a reason that these particular types of wounds refuse to heal, researchers have developed a theory involving the oxygen supply to the wound that may prove helpful.
Oxygen has a significant role in the process of wound healing inasmuch as it supplies an additional energy source for the repair process (Am J Surg, 1969; 1: 521-5; Townsend Lett Docs, 1998; 180: 66-70). During this process, fibroblasts begin to migrate, divide and produce collagen – which provides the scaffolding for wound repair. But in order for this to take place, sufficient oxygen must be present (Acta Chir Scand, 1972; 138: 109-10). In addition, oxygen is important for killing anaerobic bacteria that can lurk in wounds (Proc Natl Acad Sci USA, 1971; 68: 1024-7).
The amount of oxygen needed to repair wounds is delicately balanced. Too much can interfere with the healing process, especially early on (Exp Cell Res, 1991; 25: 101-13; Acta Physiol Scand, 1969; 334: 1-72). Nevertheless, wounds – especially chronic wounds – have been shown to have lower levels of available oxygen (Hyperbaric Oxygen Rev, 1985; 6: 18-46). Supplemental oxygen – simply breathing in pure oxygen from a mask or in a oxygen chamber, or using a topical hyperbaric oxygen treatment – can all bring about considerable benefits (Arch Surg, 1986; 121: 191-5).
But questions remain
While there is no doubt that moist dressings are currently the best way to heal wounds and reduce the risks of infection, scarring and pain, there are still questions that remain regarding some of the materials from which the current dressings are made.
Some researchers, using laboratory tests, have found that many types of synthetic dressings can be toxic to developing cells (J Biomed Mater Res, 1990; 24: 363-77; Biomaterials, 1992; 13: 267- 75) – a problem similar to that observed when such materials are used for prosthetic devices. As yet, this area is poorly researched and few have actively questioned the use of such potentially carcinogenic materials as polyvinyl pyrrolidone as ‘healing’ dressings.
This is an area of medicine that continues to evolve and the search is still on for dressings – physical barriers made from either safe synthetics or from natural materials that have a beneficial effect on wound healing.
For the best results, patients need to encourage their practitioners to opt for the least interventional approach to wound management – and remember to do the same for themselves when self-treating (see p 6 for more alternatives).
Sidebar: Superglue and more
Medicine has made many advances over the past few years and there are several alternatives to stitches. A special tape or even glue can be used to close some wounds.
Sometimes, a cut is deep enough to need some help, but not deep enough for stitches. Also, with a cut on the face, it is advisable to avoid using stitches to minimise scarring. In this case, Steri-strips or butterfly strips – very fine, thin, adhesive tapes – are a good option. These usually stay on for a few days and then fall off on their own. The only disadvantage is that they may not stay on long enough to support certain types of cuts.
Another option for wound closing is skin superglue. This method is being used more and more whenever stitches can be avoided and, like Steri-strips, has the advantage of minimising scarring. The glue goes on fast and painlessly, but the downside is that it can’t be used on areas that bend a lot, such as your knees or knuckles.
Sidebar: To stitch or not to stitch?
How do you know if a cut or wound needs stitching? The advantage to stitches is that the doctor can line up the edges of the cut squarely and cleanly, and the stitches keep the edges in place while the cut heals. This is particularly important if the cut is on a part of the body that moves a lot. If the wound is jagged or uneven, stitches are usually preferred.
You may need stitches for:
* Deep cuts [more than 0.25 inches (6.35 mm) deep] that have jagged edges or that gape open
* Deep cuts that reach down to the fat, muscle, bone or other deep structures
* Deep cuts over a joint, especially if the cut opens when the joint is moved or if pulling the edges of the cut apart shows fat, muscle, bone or joint structures
* Deep cuts on the hands or fingers
* Cuts on the face, lips or any area where there is concern over possible scarring (for cosmetic reasons). Cuts on the eyelid often need sutures for both functional and cosmetic reasons
* Cuts longer than 0.75 inches (19.05 mm) that are deeper than 0.25 inches (6.35 mm) when the edges are pulled apart
* Cuts that continue to bleed after 15 minutes of direct pressure
* Puncture wounds where the cosmetic appearance of the wound will be greatly improved or where stitching is needed to restore function, such as in an injury to a tendon or ligament.
You may not need stitches for:
* Cuts with smooth edges that tend to stay together during normal movement of the affected body part
* Shallow cuts less than 0.25 inches (6.35 mm) deep that are less than 0.75 inches (19.05 mm) long
* Puncture wounds
These wounds tend to be smaller, and stitches don’t speed healing or reduce scarring
These wounds tend to be deep, narrow and hard to clean, which increases the risk for infection. Stitching such a wound may seal the bacteria in, increasing the risk of infection
If such a wound becomes infected, it will usually drain better and heal faster if it is not stitched.
* These types of cuts need to be evaluated by a health professional, but may not always require stitching
Sidebar: Alternatives
Taking care of a wound or cut is largely a matter of common sense. When self-treating, consider these options to help support the body’s own efficient healing process.
* Stop the bleeding. The sooner you can cover the wound and slow down the blood flow, the easier the injury will be to deal with. To stop the bleeding, apply pressure that is firm and even – too much will cut off the circulation. Don’t keep checking to see if the blood has stopped; you might disturb the clotting/healing process. If there’s a lot of blood seeping through the padding you’re using, don’t remove the padding – cover it with another cloth or pad and continue to apply pressure.
Sometimes minor cuts – especially those on the head and face – bleed much more than you might expect since the number of blood vessels is greater in these areas of the body than in others. Once you have controlled the blood flow, examine the wound to determine what action is necessary.
* Keep it clean. To prevent infection, make sure that anything that touches the scrape or cut – such as hands and dressings – is as clean as possible. From time to time during the healing process, be sure to clean the wound with a gentle saline solution. You can make one at home by dissolving two teaspoons of salt into a litre of boiling water and allowing this to cool.
* In case of infection, try treating with natural antimicrobials. A good first choice is Echinacea angustifolia, which fights infection as well as promotes healing (Br J Phytother, 1998; 5: 97-104; Med Klin, 1984; 79: 580-3). Others include calendula, tea tree and lavender (Phytomed, 1996; 3: 11-8; Austr J Pharm, 1988; 69: 276-8). Pure honey may also be beneficial. Poorly healing wounds may benefit from being bathed in an infusion of camomile (Zeitschr Hautkr, 1987; 1262: 1267-71).
* Boost your protein intake. Skin is made of protein, and extra is required when you are injured. This is especially true for those undergoing an operation since surgery increases both calorie and protein needs by 20-50 per cent. Without enough protein, recovery may be delayed and the risk of infection is increased.
* Supplement. Studies show that a poor diet can retard wound healing (Am J Med, 1986; 81: 670). WDDTY panellist Dr Melvyn Werbach suggests in his book Nutritional Influences on Illness (Thorsons, 1989) that many nutrients have a role to play in wound healing. Vitamin A helps to form scar tissue, vitamin B1 deficiency can interfere with collagen synthesis and vitamin B5 accelerates the healing process. Vitamin C promotes the formation of collagen and elastin, and a deficiency can slow the healing process. Vitamin E aids in the healing of skin grafts, and zinc stimulates wound healing. Essential fatty acid deficiencies are associated with poor wound healing.
* If you have stitches. You can usually wash an area that has been stitched after one to three days. Washing off dirt and the crust that forms around the stitches helps reduce scarring. If the wound drains clear yellow fluid, you may need to cover it. Be sure to dry the site well after washing. Ointments, rather than creams or lotions, will keep a heavy scab from forming and may help reduce the size of the scar.
* Healing scars. Moist dressings should result in fewer and less noticeable scars. However, if you do have scars, silicone sheeting may be one way to help. Studies show that silicone sheets can moderately improve the appearance of hypertrophic and keloid scars resulting from surgical procedures or trauma (J Dermatol Surg Oncol, 1993; 19: 912-6). They are most effective on fresh scars (Cutis, 1995; 56: 65-7; Dermatol Surg, 1996; 22: 955-9), but should not be used until the cut has closed. Similarly, glycerine-based gel sheeting can be just as effective and less expensive (Adv Wound Care, 1998; 11: 40-3). Simply keeping scars moist for a longer period may be of the greatest benefit. Topical vitamin E oil may also help.
* Know when to call your practitioner. Cuts that require medical attention include those that: are deep (how deep is usually more important than how long); expose any red muscle tissue or yellowish fat tissue; stay open if you let go of the sides of the cut; or are sited on a joint or in an area where healing might be difficult (stitching might be needed to keep the wound closed). If medical attention is required, discuss the pros and cons of different types of dressings with your doctor. For instance, alginates are best used on wounds that are leaking lots of fluid, while hydrogels and hydrocolloids boost moisture in dry wounds. Selecting the right dressing can substantially boost healing.
