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The new ice age
Are you ready to offer your clients advice about the range of cold-therapy options available?


DVM360 MAGAZINE
Volume 39, Issue 8

Varied methods of application

There are many methods for cold application in the horse, ranging from the very simple to the complex. Research into the pros and cons of these methods is, however, lacking. Dr. David Ramey, a California practitioner, states, "No matter what the method of application, there appears to be little information available as to the effects, efficacy, length of therapy and best method of application in the horse."

Horses traditionally have been hosed off or subjected to constant cooling via a cool stream of water from a hose. Hoses with many small perforations (soaker hoses) are occasionally wrapped around a horse's leg to provide cooling. While this method has been used for years and does cool the leg, it has its problems. The tendons and ligaments can be cooled only to the temperature of the water and some sources are cooler than others. Hosing a leg or joint is slow, requires that a trainer/owner be present and stay with the horse for the required 20 to 30 minutes daily, and hosing can be a problem (physically and ecologically) if there is not a steady source of water available.

Standing a horse in a large bucket of water is another popular method of cryotherapy. This method causes a substantial decrease in limb temperature and is easier than cold hosing, but still requires a compliant horse and continual monitoring. Adding crushed ice to the water mix can further lower temperatures.

The application of ice itself is one of the best ways to cool a horse's ligaments and tendons. Ice cubes are somewhat bulky and their pressure and intense cold can be irritating to horses when wrapped on the limb. Crushed ice is better tolerated, and bags of frozen peas and carrots are commonly used, because they can be broken up when they begin to thaw and are more moldable to the leg.

Chemical ice packs actually can be colder than ice, and new technology has solved the problem with bulky, hard ice cubes. When water freezes, ice crystals form and air is trapped in the crystallized ice structure, resulting in a rigid, often irregular, shape. The First+Ice pack by MacKinnon Inc. has solved this problem. First+Ice is a mix of polymers, propylene glycol and water in a two-ply polyethylene bag with a patented breathing mechanism which lets air in and out of the bag during freezing. The result is a very cold but completely moldable ice bag that can be used along with a wrap or inserted in any number of commercially available boots.

First+Ice bags are reusable, maintain relatively constant temperature for up to two hours, conform well to the leg, are non-irritating to most horses and represent a new innovation in ice packs. There are numerous other gels and chemical ice formulations available and more to follow, but many thaw quickly, do not maintain constant temperature, are bulky and don't fit horses' legs well.

New cryotherapy devices

A number of newer devices for cryotherapy have become available recently. These relatively expensive ($3,000 to $5,000) units combine form-fitting, flexible compression wraps with a continuous cold-fluid delivery system. Game Ready and Zamar are just two of these units, allowing a constant cooling temperature with the benefit of compression. Horses are placed in wraps or boots that are attached to a central machine that pumps a coolant fluid through tubes running in the wraps.

These machines can be placed on multiple areas of the horse's body, the temperature can be set to a number of different levels and the cooling is constant. They are a bit more labor-intensive, and the horse must be relatively quiet and tolerant. Research shows that compression further reduces edema and swelling and increases the effects of cold therapy.

Less expensive compressive wrap and cold combination devices are variations on the traditional ice boot. These boots or wraps are generally a neoprene or other elastic-like wrapped piece with pockets designed to be filled with ice. Professional's Choice Ice Boots are a typical product in this coolant-device category, but with some important features that make them different. These boots are made of a high-grade Japanese neoprene that is limestone-based rather than the more common petroleum-based neoprene used in many boots. The longer-lasting, limestone-based neoprene remains soft and elastic (maximum elongation of 480 percent; human skin has only 60 percent to 70 percent elongation), and its closed-cell structure makes it 95 percent water-impermeable.

The neoprene cells are filled with nitrogen, making Professional's Choice boots better cold insulators. Better insulation and less water absorption result in more profound and consistent cooling, and in boots that do not get heavy, soggy or lose their fit during use. Because of these unique properties, horses can walk in these ice boots easily, allowing them to begin their tendon and ligament cooling while still being walked as part of their normal post-exercise cooling routine. While these boots are designed to be used with crushed ice, combining the First+Ice packs with the Professional's Choice Ice Boots results in the best of both worlds, offering compression, constant cooling for up to two hours, non-messy application and a long-lasting device.

Comparative effectiveness

But what does research tell us about the effectiveness of all these different methods of providing cold therapy? Is bigger really better? Chemical ice vs. regular ice? Buckets vs. boots? And is all neoprene really the same? Researchers at the School of Veterinary Medicine at the University of California-Davis looked at the degree and rate of cooling of tendons using a commercial compression splint with circulating coolant.

Dr. Melinda McDonald and others on that research team found that the temperature of the superficial digital flexor tendon (SDFT) dropped significantly with this unit, and that the SDFT temperature actually was lower than that of the skin. This points out a problem with cold therapy, in that there virtually is no way for the owner/trainer to tell how cold internal structures are simply by feeling the skin. It may be possible for these circulating units to cause some cryo-damage if they are used too long at too low a temperature.

McDonald sees this study as a first step and would like to see all cooling methods subjected to investigation. "With our current knowledge base", she says, "it is really more trial and error. Everyone wants an easy answer, but it's going to take some looking to see what does and doesn't work."

Nightingale has done a study that begins to address the areas McDonald identified as the major focus for future cold therapy research. She tested a continuous-coolant machine, ice packs, ice gel boots, a claylike cold wrap and simple cold hosing.

Measurements were done with a thermocouple probe, and the research team uncovered some important baseline information about the legs of normal horses. In the course of their research, they noted that temperatures in horses' legs can vary by up to 10 degrees Celsius daily, and that the leg temperature naturally decreases by six to eight degrees normally overnight. These variations are important, and must be considered when doing cold-therapy research.

In her study, the temperature drop at 15 minutes of cold application was greatest (17 degrees C) for the ice pack. Various bandages, the Zamar unit, chemical ice packs and cold hosing all showed cooling but not as much as simple ice.

Though not all studies agree, Nightingale's simple conclusion is that "the most efficient method of producing a fast and dramatic drop in temperature is to use an ice pack. Unquestionably more research is needed, but it may turn out that, for all the new innovations and high-tech devices being produced, ice in some form may still be the best way to cool your horse's legs.

Marcella is an equine practitioner in Canton, Ga.


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Source: DVM360 MAGAZINE,
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