Equine Athlete: Week 9

Image 1. Radiograph depicting slight rotation of the coffin bone

Although the horse show is currently taking over most of my time, I would like to share a quick case study before discussing the amazing, yet insane, experience that is Youth Nationals.

We have been managing a few laminitis cases this summer and I wanted to share some of what I have learned.  Laminitis, by definition, is a painful inflammatory condition within the hoof.  Laminitis occurs when the sensitive laminae become inflamed.  It is the job of the laminae to connect the hoof wall to the distal phalanx, or coffin bone.  Failure of this attachment, or even acute inflammation of the laminae, results in extreme pain as the coffin bone essentially pulls away from the hoof wall.  Chronic laminitis can result in significant separation, and eventual rotation, of the coffin bone due to the downward pressure of the horses weight (Image 1).  The 'dropping' of the coffin bone and eventual failure of the bond is called founder.  If left untreated, laminitis will eventually result in extreme rotation of the coffin bone and penetration of the sole.  It is difficult to manage severe laminitis and is therefore imperative that proper preventative measures are taken in high risk horses.

Laminitis can be caused by multiple metabolic and physical triggers.  Physical causes can include excessive weight bearing on a limb due to contralateral injury or systemic infection causing inflammation.  Acute laminitis can be induced when horses or ponies gorge themselves on lush grass or high starch grains.  The sugars from these feeds trigger the release of inflammatory mediators from the hindgut resulting in inflammation in sensitive structures, such as the laminae.  Metabolic predispositions are a lot less straightforward.  The two common culprits are Pars Pituitary Intermedia Dysfunction (PPID or Cushing's disease) and Equine Metabolic Syndrome (EMS).  PPID is caused by failure of proper communication between the pituitary gland and hypothalamaus that results in increased release of cortisol/steroid production from the adrenal gland.  Increased steroid levels can cause a reflexive constriction of blood vessels in the hoof.  This limits circulation and can compromise the supporting structures within the hoof.  Increased levels of steroids can also result in insulin resistance.  It is believed that this resistance can inhibit cells in the hoof from taking up glucose, lose energy and "stretch" as a result.  This insulin based dilemma is at the heart of laminitis caused by EMS.  Although many mechanisms are effected by hyperinsulinemia, there are a few at the root of the problem.  First, decreased blood flow to the hoof caused by activation of vasoconstriction mediators in the blood vessels.  Secondly, resistance to insulin decreases glucose in hoof cells as with PPID.  Lastly, the high insulin levels are believed to activate insulinlike growth factor (IGF) receptors on cells in the laminae.  Cells are activated to grow and change, essentially weakening the support mechanism within the hoof causing the "pulling away" of the coffin bone.  More research is being done into the exact underlying mechanisms causing laminitis to develop in horses with PPID or EMS.

Managing horses with a predisposition is a full time challenge.  It is imperative to make sure these horses have a high forage, low concentrate diet and limit grazing on lush pastures.  Maintaining a healthy weight can reduce stress on hoof structures versus overweight horses.  Hoof care is also a key factor in managing pre-laminitic and laminitic horses.  Proper hoof balance is extremely important, make sure your farrier is aware of the condition.  Periodic radiographs can give insight into how the foot is doing and help with early detection of any changes.

If laminitis occurs treatment should be quick and aggressive.  Keeping the horse on soft surfaces helps them be more comfortable (think deeply bedded, padded stall or even a flooded area of ground outside).  You can also place them in SoftRides or another padded hoof support if they will wear one calmly.  Many people will help aid in decreasing inflammation by icing the feet periodically throughout the day.  Then you can place the horse on anti-inflammatories such as phenylbutazone (Bute) or flunixin meglumine (Banamine).  One treatment that I learned about this summer was the administration of pentoxyfylline, an anti-inflammatory and vasodilator.  The goal in treatment is to get the inflammation decreased as quickly as possible and then wait and see.

Laminitis is not an easy management challenge for the owner, veterinarian, or farrier.  But, it can be done if caught early enough.  The disease itself has been around a long time, but treatment options are always evolving.  That is all I have to say on laminitis for now, stay tuned for the exciting update on Arabian Youth Nationals in Oklahoma City, OK.  Thank you for following along on my adventures!

Weeks 3-5 at Littleton Equine Medical Center

Hello again from Littleton!

It’s been very busy around here lately, as summer and the horse show season is in full swing!  I have still been spending most of my days working in the ICU, which has generally been pretty full.  Most of the horses admitted to the ICU are for various colics, but there have also been a few mares and foals, major laceration survivors, and an interesting cardiac case.  I was able to watch when Dr. Mullen, the internist, did an echocardiogram of a horse’s heart and saw an abnormal mass.  The horse had been admitted with a heart rate of 170 bpm (normal is around 28-44 bpm) with a lot of premature ventricular contractions.  Bilaterally, this horse also had thrombosed jugular veins, so had to be catheterized via the cephalic vein.  He was treated with heparin IV, oral aspirin, Plavix, and lidocaine IV and was monitored with a Holter monitor.  His jugular veins were also observed via ultrasonography to assess blood flow and the extent of the thrombi formation.  I am interested to keep learning more about his case partly because I could really use a good review of cardiology!

I have also gotten to see a lot of colic cases come through so have learned a lot lately about the different causes of colic, modalities for diagnosing them, and their subsequent treatment options.  I learned that a nephrosplenic entrapment can be treated with phenylephrine HCl (to contract the spleen) and trotting for 5-10 minutes to try to release the entrapped colon from the space between the spleen and kidney.  Also, you need to use caution when treating with phenylephrine, especially in older horses and at higher doses, because it can potentially rupture the spleen.  You can also anesthetize the horse and physically roll it around (I haven’t seen that one yet but that would be neat-o) to try to free the entrapment as well.

On Mondays, I spend the day in the field with one of the veterinarians.  Sometimes, the day is mostly filled with farm calls and other days many of the cases are at the clinic.  Last week, I spent the day doing repro work with Dr. Dietz.  We spent the first part of the day checking mares and it was a really good review of horse reproduction.  I spent two years in grad school learning the finer aspects of sheep reproduction and estrus synchronization, and this was a great refresher of how mares are opposite of sheep and cows in many, many ways.  Even mares’ ovaries are inside out.  One mare that we saw was suspected to have a uterine infection, so Dr. Dietz took two swabs of the uterus; one for cytology and one to be cultured.  She then lavaged the uterus with sterile saline and treated the mare with enrofloxacin (a broad spectrum antibiotic), dexamethasone, and oxytocin.  When we went on some farm calls to check local mares and on one particular mare, Dr. Dietz saw that she had an ovulatory follicle and lavaged her then checked again afterward and saw that she happened to ovulate while being flushed.  It was really neat to see what a freshly ovulated follicle/corpus hemorrhagicum looks like.

I know it’s really common, but I got to see a Caslick’s procedure performed for the first time that day too.  Dr. Dietz did the closure with a Ford interlocking pattern, which is less complicated than I imagined it would be.  Caslick’s procedures are useful for mares that have poor vulvar conformation or are prone to pneumovagina, both conditions of which predispose them to infections of their reproductive tract.  Later in the day, we went to a farm for a colic emergency, and Dr. Dietz quizzed me on colic types and treatments along the way.  Once there, she diagnosed a small impaction via rectal exam, and we passed a nasogastric tube to administer a bolus of fluids and electrolytes as well as some mineral oil.  The mare ended up recovering well overnight.

One emergency farm call that I went with Dr. Harbourd on involved an older pony that was down and could not rise.  I learned a useful recipe for a “Lazarus cocktail” that can be administered IV and is comprised of butorphanol, banamine, calcium gluconate, and dextrose with fluids to help a downed horse.  This cocktail provides pain relief, fluids (if they’ve been down for a while, they’re likely somewhat dehydrated), and easily utilizable energy.  Fortunately with the help of Dr. Lori and some butorphanol, we were able to get the pony up before administering it.  More useful information that I learned on that farm trip was that you should do your best to move the front end of the horse or pony away from the wall or corner of the stall, because they need a good amount of space in front of them to get up.

As always, the Monday morning meetings have been full of great information.  Lately, we have learned about field management of colics, colic diagnostics, and how to minimize the risk of veterinary misadventures (as well as how to resolve them if they do occur).  This morning’s talk in particular was extremely useful.  One of my major concerns about being a new graduate within a few years is how to recognize and resolve complications as they arise.  This morning, Dr. Toppin taught us how to recognize and treat an anaphylactic reaction, how to minimize the risk of inadvertently doing an intra-carotid injection, and how to treat vaccine reactions.  I feel better about being able to recognize when a complication has arisen, and about how to go about treating it one day if it occurs.

Last week, I spent Monday working with Dr. Toll doing farm calls.  First, she repaired an uncomplicated laceration below the stifle, trimmed proud flesh from a heel bulb injury on the same horse, and applied chlorhexidine ointment as a treatment to help prevent the reoccurrence of proud flesh (excess granulation tissue).  At another farm, I scrubbed the site for IRAP injection at the lateral femorotibial joint and learned that the landmarks are the lateral collateral ligaments, lateral patellar ligament, and tibial plateau ventrally.  IRAP is useful for treating osteoarthritis and general joint inflammation by stimulating the horse’s own immune cells to produce anti-inflammatory mediators.  She also floated an older pony’s teeth and I learned how to open a horse’s mouth more easily without getting my hand gnawed off.  At the end of the day, we saw a horse that had an allergic reaction to who knows what in its stall.  Its eyes were nearly swollen shut and its muzzle was so inflamed that it was squeezing out past its halter.  It also had hives over the rest of its body.  She treated it with an IV injection of dexamethasone and oral hydroxyzine (an antihistamine).

Also, I got to see a DDFT tenotomy done on a horse with chronic laminitis.  This procedure is a salvage procedure, and the purpose is to reduce the backward pull that the DDFT exerts on the coffin bone.  It was performed as a standing procedure, and the vets also worked with the horse’s farrier to see that it was outfitted with heartbar shoes and the dorsal hoof wall was trimmed back to improve the breakover in the horse’s foot.

Anyhow, I’ve learned a ton so far and am excited to keep seeing and helping with more here.  I’m sad that my time here is officially halfway over but hope you’re all having a great summer as well!

-Calli

Equine Athlete: Weeks 7-8

After two hectic weeks at the Regional shows we all took a day to recover over the 4th of July holiday.  Then it was back to work catching up on local patients and beginning preparation for Youth Nationals.  There have been many opportunities to see and learn new things over the past few weeks.  The doctors have been fantastic teachers and are always willing to talk me through the procedures that they are doing.  We have gotten to see some fun things over the past two weeks.

Regional limb perfusion

It all kicked off with a regional limb perfusion.  I have heard of the procedure but was excited to be part of one.  Regional limb perfusion (RLP) is often used in large animals to deliver medication or antibiotics to specific areas versus systemic administration.  More recently RLP has been used to deliver stem cells to areas with tendon or ligament injuries.  The Quarter Horse gelding was perfused with mesenchymal stem cells in order to help in the healing of a chronic injury to the suspensory branches.  Mesenchymal stem cells have been shown to increase the rate of healing in tendon and ligament injuries.  It is believed that the properties of stem cells draw mediators and cells to the injured area to promote healing.  In order to perform the RLP Dr. Hill placed a tourniquet distal to the carpus and perfused via the lateral palmar digital vein.  We then left the tourniquet on for 30 minutes under a wrap over the injection site.  When the treatment was complete we wrapped the leg with a pressure wrap and administered some banamine.  Hopefully this procedure can offer our patient some relief.

Dr. Hill performing an ultrasound exam

At one of our next stops we got to follow up with a horse that had damaged its suspensory ligament.  Before this summer I had very little experience with ultrasonography beyond reproductive imaging.  Dr. Hill has been a fantastic instructor and has kindly walked me through his exams.  This particular case involved a gelding that became acutely lame at a horse show earlier this season.  He had a history of suspensory soreness but always responded to shockwave therapy, icing, and other management practices.  He was given time off prior to the show season in order to rest the area and prevent major injury.  Unfortunately, a bad step off of the trailer had the farm calling Dr. Hill.  Upon exam we were able to pinpoint the area of acute soreness in the lateral branch of the suspensory ligament.  Ultrasound examination revealed significant edema within the branch.  The farm was instructed to rest the horse in its stall for 30 days with daily icing.  When we were next out at the farm we performed a follow-up exam.  It was great to see the side-by side comparison of the injury.  Healing was easily visible between the images and the horse was cleared for two weeks of hand-walking and a slow return to work.  Before we left we shock-waved the area to kick-start further healing.  We will be back to re-examine the horse and hope to see even further correction.

The level of care, from farm to show ring, that is offered at Equine Athlete has provided me a full circle view of this kind of equine medicine.  It is a unique opportunity to be able to follow cases throughout my internship and learn, not only about diagnostics, but treatment and long term management of various ailments.  I am very fortunate to have been given this opportunity and look forward to my final month with the Equine Athlete team.

Equine Athlete: Weeks 5-6

Hello from Lexington, Kentucky and the Region 14 Championships.  We have spent the last two weeks away at regional shows.  Last week Dr. Hill and I were in Springfield, Ohio for Region 13.  This week the whole group is together in Lexington for Region 14, a much larger show.  The days are full of various activities and no two days are the same.  We are the show vet here at 14 and therefore we see everything from our traditional lameness case, to colic cases and unexpected show injuries.  This week has also given me the opportunity to become more familiar with treatments that get done at shows versus at home.

One of my main duties has been to perform the laser treatments on different horses.  I have now become very familiar with the equipment and treatment options.  Typically, I have been treating sore backs, fetlocks and feet.  This week though, I have had the opportunity to treat some wounds.  One of my favorite laser cases involved a horse who rubbed his tail on the trailer ride to Lexington.  When we first examined the damage we couldn't believe he had managed to scrape himself up so much.  By the time we looked at it there seemed to be a possibly bacterial component and a lot of hair loss.  We cleaned the area and prescribed sulfadiazine, or SSD, cream (an antibiotic and protectant).  The horse was scheduled to show later that week, and therefore we needed to help speed up the healing process.  He was put on my laser schedule and I got to work.  Every morning I would arrive and asses the wound, clean it with soap and water, and then laser the area.  I am pleased to announce that after a few days of proper care and lasering, the area is looking much better.  Note the decrease in redness and lack of irritation after only one day of treatment.

Image 1. Day 1

Image 2. Day 2

The shows finished up without any major cases of travel or show related illness.  I have been told not to count on such luck as the show season progresses and the weather heats up.  Our next big show is Arabian Youth Nationals in Oklahoma at the end of July.  The weather is going to be brutal, and therefore cases of shipping fever and colic will most likely be numerous.  So I am sure I will have time to broach that subject when we get to Youth.  For now I will sign off from the road as we head to our next big farm prep.  This week and next will be spent preparing everyone for Youth and catching up on our smaller farms more locally.  We have already seen some interesting cases that I am looking forward to sharing with you all soon.  So stay tuned and have a great week!