Bringing a horse back into condition after some time off must be done carefully: He needs to work up a sweat to increase fitness, but too much exertion increases the risk of several serious complications, including tying up.
Tying up—technically called exertional rhabdomyolysis—refers to severe cramping of the large muscles of the hindquarters, back and sometimes the shoulders during or after exercise. In some cases, damaged or dying muscle cells can release enough toxic debris into the bloodstream to stress the kidneys. Extreme cases may be fatal.
Repeated tying up can occur in horses with specific disorders characterized by cellular dysfunctions in the muscles, such as polysaccharide storage myopathy (PSSM) and recurrent exertional rhabdomyolysis (RER). However, heat stress and/or electrolyte imbalances can cause virtually any horse who exerts himself to tie up under the right conditions.
Here’s what to do.
Call your veterinarian if …
• your horse comes to an abrupt halt with massive muscle cramping, usually over the hindquarters. Or if he stiffens up and moves forward only reluctantly, perhaps taking only short strides and stabbing his hind toes into the ground. These are classic signs of tying up.
• he sweats profusely, with less sweat over the affected muscles.
• he has a pained, “colicky” look, with rapid breathing and a fast heart rate.
• he develops muscle tremors.
• his urine is discolored —from a reddish tinge to a dark, coffee-like hue.
As you wait for your veterinarian …
• Keep the horse still. A horse that is tying up cannot “walk off” these cramps, and forcing him to move may cause further injury to his muscles. Keep him standing right where he is until your veterinarian arrives. If you must move the horse for safety or to get treatment, bring a trailer to him and move him only the minimum number of steps.
• Encourage him to stay calm. Keep a buddy with the horse that is tying up or offer him small bites of hay. Stress can make this condition worse, so do what you can to make the environment soothing.
• Offer water, possibly with electrolytes. Water with dissolved electrolytes may be helpful, if your horse will drink it. If he won’t, offer him plain water, too.
• Warm up or cool down the affected muscles, according to the season. If it’s a hot summer day, sponge cool water over a horse that is suspected to be tying up. (Contrary to the old myth, splashing cold water on hot muscles will not cause further cramping.) In cold weather, place a blanket over your horse’s hindquarters to warm him up.
• Watch for urination. The color of the urine will offer important diagnostic information for your veterinarian. If your horse urinates while you’re waiting for her to arrive, take note of the color or, better yet, catch some in a clean, empty container.
• Monitor your horse for other complications. The metabolic imbalances associated with fatigue can lead to other issues as well. Synchronous diaphragmatic flutter, called “thumps,” is one possibility—look for a distinctive jerking, or tic, in your horse’s flank that matches the rhythm of his heartbeat. Hyperthermia (overheating) can develop when a horse can no longer cool himself by sweating—look for agitation, panting through the mouth, excessive sweating and skin that is noticeably hot to the touch. Dark mucous membranes and skin that does not snap back into place after being pinched are signs of serious dehydration. A horse who is exhausting his fluid reserves may also develop anhidrosis, the loss of the ability to sweat. If you notice any of these other signs starting to develop, call your veterinarian with an update; she may decide your case is becoming critical.
What NOT to do
• Do not administer any medications. If your horse is tying up, it may be tempting to try to relieve his pain with Banamine or phenylbutazone, but you may only add stress to his kidneys. Plus, you may mask signs that your veterinarian needs to see to get an accurate diagnosis.
• Do not massage the horse. Rubbing the hardened muscles of a horse that is tying up will be painful and may only make the situation worse. The cramping will ease on its own in time, and your veterinarian will administer intravenous fluids to support his kidneys as well as medications to help the muscles relax.