Laminitis can strike anytime, but in the spring, when fresh grass is sprouting and horses are spending more and more time turned out, the risk of this painful, potentially fatal condition rises sharply. The reason is that new grass contains high levels of a complex sugar called fructan, which horses are unable to digest. As a result, a bellyful of spring grass can upset the bacterial balance of the equine gut, causing metabolic upheaval that precipitates laminitis, an inflammation of the sensitive plates of soft tissue (laminae) in the horse's foot.
With careful management of your horse's diet--both roughage and grain--you can help to protect him from the cascade of events that leads to laminitis. But some horses develop the disease despite the best of care. In those cases, time is a critical commodity; the earlier you can recognize the signs and begin treatment, the greater your horse's chance of survival.
The classic clinical signs of laminitis--extreme reluctance to walk and a stance in which the hind legs are well under the body to take pressure off the front hooves--are hard to miss. But there are two other more subtle signs that can help you recognize impending trouble much earlier: Increases in a horse's blood pressure--and in most cases, pulse strength--often mean laminitis is imminent.
Here are two simple techniques you can use to monitor these vital signs. Each requires some practice both to apply and to interpret the results. Once you've established your horse's baseline readings when he is healthy, you need only take his blood pressure and pulse when you suspect a problem. If your horse has a history of laminitis, however, it's a good idea to regularly monitor both indicators during high-risk periods. In the spring and after late-fall rains, take readings twice a day if you can. Should you discover elevated blood pressure and/or pulse, call your veterinarian immediately. The sooner treatment in initiated, the greater the chance of lessening the severity of laminitis.
Taking a Horse's Blood Pressure
The blood-pressure cuff is an accurate, but underutilized tool in detecting laminitis. The average horse's systolic reading, which indicates the force of blood pumped from the heart, will remain between 110 and 120. (Diastolic pressure is rarely an indicator of disease in horses.) Early in an episode of laminitis, a horse's blood pressure shoots up by 20 to 30 points or more as blood is forced through the constricted vessels within the hooves. This increase occurs as much as 12 hours before the obvious physical signs of laminitis appear, a small window of time to begin aggressive treatment that may prevent the worst damage.
For this procedure, you'll need a manual pediatric blood-pressure cuff (sphygmomanometer), available at some pharmacies and most medical supply stores. The device we used cost $30.
1. To take a horse's blood pressure, place the cuff under the tailbone at the point where it is least tapered. Be sure to put the bladder of the cuff, where the tubes enter, on the underside of the tail.
2. Use the cuff's Velcro closures to secure it. Make it snug but not too tight so that it exerts about the same pressure that a tail wrap would.
3. Make sure the valve by the bulb is closed and pump the bulb until the pressure reads 160 or greater.
4. Then crack the valve very, very slightly so air leaks extremely slowly. If you let air escape too quickly, you won't be able to get a reading.
5. As the cuff deflates, watch the needle fall. At certain points, it will hesitate before dropping again. Eventually, the needle will hesitate, then bounce upward to a higher reading before dropping again. That bounce is caused by the blood in the underside of the tail pressing against the cuff. The number at which the needle first hesitates before bouncing up again is the horse's systolic blood pressure.
Monitoring the Pulse
A strong pulse can mean a few different things. If the pulse is stronger only in one leg, for example, chances are an infection--from a wound or abscess, for instance--is present. A bounding pulse in both front legs, however, is an early sign of laminitis, especially when the blood pressure is also elevated. Taking a horse's pulse isn't simply a matter of putting a finger to an artery, however. Equine blood vessels can be difficult to locate; you'll need to master a three-fingered technique to glean the most useful information. Be prepared: Taking an accurate reading of a horse's pulse requires lots of practice.
1. You can feel a horse's pulse on both his front and hind legs just over his sesamoid bones. The closest pulse point to the hoof that is relatively easy to find, this is the best place to feel for the throbbing pulse that comes with laminitis. Place your three fingers on the inside of the widest point of his fetlock. You'll feel a large vein (which doesn't have a pulse) and possibly a nerve, with the normally thinner artery resting between them. Press the vein flat to feel the pulse in the artery.
This technique is effective no matter where on your horse's body you take his pulse. Place three fingers along the artery, pressing hardest with the finger farthest from the heart, slightly less with the middle finger and barely pressing with the last finger. By largely restricting the artery with the finger farthest from the heart, you'll amplify the pulse somewhat, making it easier to feel. (Making the pulse stronger won't confuse your interpretation if you do it every time; it's the leg-to-leg and day-to-day comparisons that are important.) If you don't use this gradient pressure across your fingers, you may not be able to find a pulse, and even if you do, you won't be able to judge how strong it is.
2. Another pulse point on the front legs is located on the inside of the knee, just behind the bony "knob" of the joint. Again, you'll have to push aside a vein to feel the artery, but it may be easier to find the pulse at this location than at the fetlock.
3. The hind-leg pulse can also be taken on the cannon bone, where an artery lies between the splint bone and the leg bone. Look for the pulse about three quarters of the way up the cannon bone; farther down it's harder to locate. This is the easiest leg to pulse to find and a good place to practice your technique.
4. You can also place three fingers of each hand on either side of your horse's face. The artery you want to feel runs horizontally across the face, just below the cheekbones. Feel for it behind where the halter cheekpieces sit. This final pulse point won't help detect laminitis, but it can give you a general sense of your horse's cardiac function and is extremely easy to detect.
This article originally appeared in the May 2000 issue of EQUUS magazine.