Bob Childs - ESA/AHA/PHCP Certified Hoof Specialist


Are Drugs Effective for Acute Laminitis?
By admin | | Laminitis |

Article by: Nancy S. Loving, DVM March 18 2009, Article # 13802

At the 2008 AAEP Convention, which was held Dec. 6-10 in San Diego, Calif., Bill Moyer, DVM, professor of sports medicine and head of the Department of Large Animal Clinical Sciences at the Texas A&M College of Veterinary Medicine and Biomedical Sciences, presented a variety of considerations on the state of medical treatment for laminitis. He stressed that once clinical signs are evident, damage has already been done: Pain and lameness are preceded by vascular and structural damage within the hoof laminae (lamellae).

So, he posed the question to the audience, "Is any specific medical treatment for acute laminitis efficacious in altering the outcome after a horse has developed clinical signs?"

Is any specific medical treatment for acute laminitis efficacious in altering the outcome after a horse has developed clinical signs?

The current consensus on effective therapy revolves around addressing and resolving the initiating cause(s) of laminitis. Other strategies attempt to alter blood flow in the foot, decrease inflammation, and avert endotoxemia. Moyer addressed these in his talk.

He explained that evidence is lacking about blood flow-altering agents having any effect on increasing laminar circulation. While use of digital nerve blocks might improve blood flow by inhibiting constriction of blood vessels, numbing the pain stops the horse from protecting his feet. Increased weight bearing exacerbates laminitis.

Acepromazine increases digital blood flow by direct action on vascular smooth muscle, but studies have not shown improvement in lamellar blood flow.

Isoxsuprene has vasodilating properties, while pentoxyfylline requires weeks of administration to decrease blood viscosity. It does this by acting on platelets to increase red blood cell flexibility. Both these medications are absorbed poorly when administered orally.

Nitroglycerin placed over digital blood vessels might increase blood flow, but it has not been shown to increase lamellar blood flow after the onset of clinical signs. Coupling this ineffectiveness with potential risks to the person handling the drug makes nitroglycerin a poor therapeutic choice. Heparin removes red blood cells from the system to decrease blood viscosity and thereby improve blood flow, but researchers have not examined its use in acute cases.

Inflammation is not always a component of laminitis, but when it is, non-steroidal anti-inflammatory drugs (NSAIDs) have been used. Moyer said there is humane justification for judicious use of NSAIDs, but one should be aware of downsides. Pain relief might increase mobility that exacerbates tearing of the lamellae.

Phenylbutazone (Bute) might reduce inflammation and pain, and it is affordable, but it does not prevent laminitis if given during the developmental stage and has not been shown to alter the course of acute cases.

Flunixin meglumine (Banamine) provides both anti-inflammatory and anti-endotoxin effects. However, if flunixin and phenylbutazone are given together, there is an increased risk of loss of serum protein, gastric ulcer disease, and/or colitis.

There is anecdotal support for use of dimethyl sulfoxide (DMSO) for its anti-inflammatory properties and ability to scavenge oxygen-derived free radicals, which form during hypoxia (deprivation of an adequate supply of oxygen) and reperfusion (restoration of blood flow to tissues following an incident or hypoxia). Damage can occur when blood flow is restored to tissues following an incident of reduced blood and oxygen supply. However, Moyer noted there is no evidence of hypoxia or reperfusion in this disease.

Anti-endotoxin drugs (flunixin meglumine, ketoprofen, and polymyxin B) might be warranted as there is an association between endotoxemia and the development of laminitis. Endotoxin causes insulin resistance with decreased use of glucose by the lamellar tissue. While they might not necessarily be effective in treatment of laminitis, anti-endotoxic drugs might be life-saving.

Moyer said caretakers and veterinarians should address environment and ground surface, housing, causes of obesity, and management of the foot itself. He recommends explaining to clients that the pathogenic mechanisms of laminitis are not well-understood and that a horse's clinical appearance might correlate with the outcome, but it is not always an accurate predictor due to potential for complications.

In general, controlled studies do not exist regarding the efficacy of various treatments for laminitis, and some therapies have additional risks beyond their failure to improve the situation.

Pathophysiologic and Therapeutic Implications of Endothelin-1
By admin | | Laminitis |

Endotoxemia and the roll of ET-1 in acute Laminitis

"Although administration of a low-dose of endotoxin to horses causes a significant decrease in laminar perfusion and digital blood flow, there have been no repeatable models of endotoxemia that consistently induces acute laminitis. However, diseases that are often complicated by laminitis are accompanied by endotoxemia (intestinal strangulating obstruction, anterior enteritis, enterocolitis, pleuropneumonia, and metritis). In a study in our laboratory, we demonstrated a significant decrease in digital arterial blood flow from 30 min to 2 h after administration of a low dose (35 ng/kg over 30 min) of endotoxin to conscious horses. There was a concomitant decrease in digital arterial blood pressure from 30 min to 1.5 h after endotoxin infusion. These digital hemodynamic effects were accompanied by a significant increase in cephalic venous plasma ET-1 concentrations. These findings suggest that perhaps endotoxin does play a role in initiation of the early hemodynamic alterations in laminitis, and that this may be at least partly mediated through increased synthesis and release of ET-1."

Authors: Susan C. Eades, DVM, PhD; Ashley M. S. Holm, DVM; and Rustin M. Moore, DVM, PhD

Laminitis: New Study on Sugar and Starch as a Cause
By admin | | Laminitis |

Kathryn Watts says: "As with humans, diet and exercise are the only way that insulin resistance, which causes high levels of circulating insulin, can be managed."

Read the article: Laminitis: New Study on Sugar and Starch as a Cause

Metabolic Syndrome in Horses
By admin | | EMSLaminitis |

Article by: Philip J. Johnson, BVSc, MS, MRCVS, DACVIM

Affected horses tend to be aged between 6-to-20 years and there does not appear to be a sex predilection. The problem is reported more commonly in some pony breeds, domesticated Spanish mustangs, Peruvian Pasos, Paso Finos, European Warmbloods, American Saddlebreds, and Morgan horses. Affected horses are commonly obese and develop excessive adiposity at specific locations, especially in the crest of the neck, at the shoulders, above the gluteal muscles, and in the sheath (geldings). Female horses are notoriously difficult to breed and exhibit abnormal ovarian cycling behavior. Horse owners refer to many of these horses as "easy keepers" and vigorously contend that all efforts to reduce the horse's obesity by dietary restriction are futile. Ample intra-abdominal (omental) adiposity is evident during ultrasonographic examination of the abdomen or at necropsy of affected horses.

Many of these horses are presented to veterinarians for diagnosis of lameness attributable to laminitis. There is a very strong association between the development of obesity, metabolic syndrome and the risk for developing laminitis. Commonly, at initial veterinary examination, there already exists both physical and radiographic evidence for long-standing laminitis in these horses although reputable and credible owners and managers report that there have been no prior signs of laminitis or any obvious explanation. Metabolic syndrome is often recognized incidentally when horses are presented for other reasons, such as routine health care or other medical problems. In these horses, visible changes in the hoof that are commonly attributable to laminitis (including prominent growth lines, palmar divergence of growth lines, and a convex sole) may be evident in the absence of laminitic pain or any history of laminitis or lameness. There are minimal hematological changes in horses affected with metabolic syndrome (unless laminitic pain is prominent). Abnormal results of routine serum biochemical profiling might include a slight-to-moderate elevation in the glucose and triglyceride concentrations.

Laminitis and Obesity
By | | Laminitis |

Interesting comments on laminitis and obesity by Donald M. Walsh, DVM

"Based on my experience observing laminitic horses over the past 36 years in veterinary practice, I believe that obesity leads to the development of weakened laminae and other supporting structures of the foot and to changes in the growth pattern of the feet. 2 Radiographs reveal that the appearance of the laminae begins to change in horses that are becoming obese, even before any signs of lameness from laminitis are observed.

Perhaps, when a horse becomes obese, there is a messenger substance that promotes or allows for the skin's basement membrane to stretch so the skin can "enlarge itself" in order to accommodate for the increased layer of fat under the skin. If this is so, perhaps this same messenger substance is also recognized by the epithelial laminar basement membrane in the foot, which would cause the basement membrane to stretch, which could result in the weakening of the laminae of the foot in the obese horse. These weakened feet are much more susceptible to grass laminitis and other predisposing insults known to cause laminitis.

Obese horses need a major change in lifestyle in order to become healthy. Accomplishing this can be a challenging task for the owner because weight reduction in these horses requires a low caloric diet together with a considerable amount of exercise. Many of the horses experiencing laminitis are so sore-footed that much exercise is not possible. Many live lives of constant pain associated with ongoing bouts of laminitis, which finally results in so much damage to the feet that recovery is impossible. These (heavy-type) horses are the most common group associated with the ingestion of grass as a cause of laminitis."