Managing Acute and Chronic Laminitis, AAEP 2008

With a packed room of veterinarians at the 2008 American Association of Equine Practitioners convention, held Dec. 6-10 in San Diego, Calif., facilitators Jim Belknap, DVM, MS, Dipl. ACVS, PhD, an associate professor in the Department of Veterinary Clinical Sciences at The Ohio State University, and Rob Boswell, DVM, of Palm Beach Equine Clinic in Wellington, Fla., opened discussion about preventing and treating laminitis. Belknap remarked on the latest research showing that laminitis is an intense inflammatory injury of the foot and is no longer believed to be solely a blood flow problem. It is known that even though a horse with imminent laminitis might look normal and as yet show no lameness, inflammatory mediators are already elevated by up to 1,000-fold in the laminae.

With that in mind, Belknap is an advocate of administering very high levels of anti-inflammatory medications (500 mg three times per day of flunixin meglumine) within the first 72 hours. Belknap realizes that this high dose is more likely to lead to some gastrointestinal (GI) ulceration and, thus, it should not be used on every horse. But he stresses that it is critical to get foot inflammation under control and ulcers might be the lesser of two evils. Once the acute stage has settled down, it might be desirable to switch to phenylbutazone for better pain relief.

Ice can be beneficial for the same reason that hypothermia is used in some types of inflammatory injury in human medicine: hypothermia is anti-inflammatory and slows down the metabolic rate (i.e., enzyme activity) of injured tissue.

There might be a great benefit to getting the feet on ice immediately to decrease the activity of deleterious enzymes, such a MMPs (matrix metalloproteinases), and to decrease inflammation. Studies show that the best means of cooling the feet is by using a bucket arrangement or wrapping the hoof in a 5-liter plastic bag or truck inner tube filled with ice and water. Refresh ice continually as needed. The table topic facilitators stressed that no harm can come of keeping feet in ice for 72 hours--as much ice therapy as possible is desirable in averting the inflammatory effects related to acute laminitis. After 72 hours no ice is necessary and, in fact, it might be counterproductive to soften the foot with water soaks. The horse should not be walked during the acute phase.

Dimethyl sulfoxide (DMSO) is used commonly, but there is very little research to support this drug's use. In an already laminitic horse, DMSO might have anti-inflammatory properties due to it being a superoxide radical scavenger, and it might work as a vasodilator. It can be given either orally or intravenously (IV) with good absorption.


Belknap noted that previously 10% of laminitis cases were linked to pasture-associated obesity, while now this has increased to 60-70% of cases.

Equioxx is a new NSAID that targets COX-2 inflammatory mediators. Belknap advised that this drug needs five to seven days to reach a steady state of effect, but if given at a triple dose initially, the steady state can be reached in 24 hours. Until research is performed on its effects in the early stages of laminitis, it might be best used on nonacute cases due to concerns about its potential to exacerbate deleterious vascular events (like Vioxx did in at-risk humans) in the horse at risk or in the acute case of laminitis. Equioxx should be very advantageous for treating chronic cases, as there should be many fewer side effects due to a lower incidence of gastrointestinal ulceration or kidney lesions when compared to the other non-steroidal anti-inflammatory medications (NSAIDs). However, it was also mentioned that COX-2 mediators are needed to heal gastric ulcers, so there is some concern about giving the drug to horses that are known to already suffer from GI ulcers.

Blood flow might not play as predominant a role as once thought in laminitis, so vasodilator therapy is not necessarily as important as some of the other treatment choices. Acepromazine only opens vascular beds for about 40 minutes following intramuscular (IM) administration, so if given, it should be administered at least four times a day. Another possible vasodilator to use is IV lidocaine. Both practitioners feel that a single dose of dexamethasone (a steroid analog) in a horse at risk of laminitis might help decrease inflammation considerably in the feet, but they are resistant to use it due to litigation regarding steroid use and laminitis.

The facilitators and audience next examined foot support of laminitic horses. Boswell prefers the two-part putty mixture material placed generously from the tip of the frog to the back of the frog and into the sulci. This recruits not only the frog but also the sulci for support. There was mention that "Soft-Ride" pads give a horse with acute laminitis a good measure of relief, but these only provide contact with the frog, so it also helps to use impression material within the sulci.

Lidocaine nerve blocking of the front feet on the initial visit allows the veterinarian to assess any hind limb involvement, pull the shoes, and take radiographs. Belknap suggested that veterinarians use lidocaine for the nerve block due to its short period of action. Shoes left in place might apply too much pressure on the hoof wall and laminae. Removal of the shoes also allows the practitioner to obtain good X ray images to evaluate the internal components of each hoof. Prognosis of foot health and integrity is achieved by comparative views of radiographs (both lateral and dorsopalmar views) taken within the initial three to five days of a laminitic attack. Measurements of the distance from the dorsal hoof wall (the outside of the hoof wall at the toe) to the dorsal border of the coffin bone assist the practitioner in evaluating the integrity of the laminae within the hoof capsule and in determing if there is any displacement or rotation of the coffin bone.

Boswell suggests serial radiographs every week for four weeks. If there is a 25-30% decrease in sole depth during this time, this is not considered a good prognosis for the horse and the situation is likely to end up as terminal. If there is less than 6-7 mm of sole, treatment may fail to alleviate the crisis. If a horse is not progressing well despite aggressive therapy, a venogram might be a helpful tool to determine if there is remaining circulation in the front of the hoof and, if not, then euthanasia might be indicated. However, not all veterinarians agree, and it was stated that some horses have been saved that appeared to have no chance on venogram results.

If the shoes are left on, the back of each foot should be filled with cushion support substance (such as the two-part putty) from the tip of the frog back. The hoof should be placed on the ground so the material fills the spaces within the frog and any extra oozes out to avoid applying excess pressure. In the early stages a horse undergoing rotation can be placed in a temporary raised heel shoe, such as the Nanric modified Ultimate (taped on), but both practitioners recommend unscrewing one wedge from this shoe to make it shorter for horses whose coffin bones have both rotated and undergone sinking. The objective is to stabilize and derotate the coffin bone as much as possible to relieve forces, while providing support to internal structures of the foot. Both clinicians emphasized that you need to watch the horse's response to the shoeing, and they said there is not one type of foot support that works for every horse.

In their discussion on chronic laminitis, the pracitioners noted that such horses have a mechanical problem that can't be fixed chemically at this point. The best approach is using special shoes. A great deal of audience discussion centered around using the wooden clog shoe--either a "homemade" shoe with 1 1/8" plywood, beveled 45 degrees all the way around, or the commercially available EDSS (equine digital support system) product. These are screwed in on the side of the hoof wall, and just enough cushion impression material is placed in the frog area to give relief without too much pressure. Such a shoe is purported to absorb concussion and allow the horse to adjust how he wants to stand, possibly more than other shoeing options do. Again, Belknap and Boswell pointed out that they use many different types of shoes in chronic cases, and one shoe does not work on all cases.

Belknap has noticed that previously 10% of laminitis cases were linked to pasture-associated obesity, while now this has increased to 60-70% of cases. He cannot find an explanation for that trend, and no one in the audience had any suggestions.

About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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