Colic and the Endurance Horse, Part 2
By Ann Stuart, DVM
This article will present a general overview of the options considered by a treatment veterinarian when an endurance horse has colic. In Part 1 we discussed types of colic specific to endurance horses and how they are evaluated. It is important to understand that every case is unique, and often the treatment plan will evolve as the clinical picture changes.
The first area to address is hydration and electrolyte status. As most fluid and electrolyte losses occur in the first part of a ride, it is easy to see that dehydration can become devastating to multiple body systems if not corrected. Ileus, or lack of movement of the intestine, can often be effectively treated with large volumes of fluid replacement with appropriate electrolytes included in the IV bags. In general a dehydrated endurance horse will require 20 to 40 liters of fluids to correct a deficit, and over a period of hours, that much again to resolve ileus, impaction, kidney and muscle compromise that can all occur together.
With the availability of portable blood analyzers, some treatment vets are able to correct specific electrolyte abnormalities that are identified. Total protein and packed cell volume can provide more specific details of hydration status.
Without blood analysis available, clinical parameters including pulse, mucous membrane characteristics, capillary refill time, skin tenting and urine output are constantly reevaluated to guide the course of fluid therapy. Simply replacing lost fluid volume with a balanced IV electrolyte solution can often provide enough support for physiologic imbalances to be corrected.
Another diagnostic tool that can also be used therapeutically is the nasogastric (NG) tube. In a horse with suspected ileus it is important to decompress the stomach, which may overfill to the point of rupture because ileus has prevented gastric emptying. In horses without ileus it is possible to administer fluids and electrolytes through an NG tube. Small amounts of fluid, five or six liters, can be given safely every 45 minutes or so as long as the stomach is emptying at a normal rate. If the horse has an impaction somewhere in the gastrointestinal tract, laxatives such as mineral oil, psyllium or magna-lax can also be given via the NG tube.
As far as medications are concerned, clinical findings and how the case progresses will determine what is administered. Flunixin meglumine, aka Banamine, helps patients with colic in two important ways. First of all, it is a potent painkiller that can relieve mild to moderate symptoms. This can help the gut return to normal function by breaking the pain cycle, allowing the intestines to relax. Sedatives and other painkillers may also be needed to provide some pain control.
Secondly, flunixin in smaller doses has an anti-endotoxin effect. Horses with colic and endurance horses in general have often been found to have endotoxemia. This is a condition where toxins released from dead bacteria can enter the bloodstream with devastating effect, most often laminitis. Flunixin and other medications such as Polymixin B and DMSO are also useful in curbing the effects of endotoxin.
That being said, flunixin can also be a very dangerous medication when administered to a dehydrated endurance horse with colic. Kidney damage can be a side effect of flunixin, like other non-steroidal anti-inflammatory drugs. Another side effect can be ulceration of the GI tract. Combine these risks with potential kidney damage that can result from a concurrent case of myositis or tying-up, and you compound some real risks. Therefore flunixin will often be given in reduced doses until dehydration is corrected. Realize that the treatment vets have their hands full sorting all of this out to resolve all of the problems that can arise in a complex colic case.
In the extreme and unfortunate circumstances that a patient does not respond to the therapy provided at the ride site, referral to a hospital may be necessary. Indications for referral are a lack of response to therapy, deteriorating condition, persistent reflux from the NG tube, abnormal rectal exam findings, a need for further diagnostics or simply the need for more support staff to manage the case.
At the referral hospital, records sent with the horse as well as direct communication with the referring treatment vet will help the veterinarians at the hospital formulate a plan for therapy. It may be that the colic patient simply needs prolonged medical therapy and ongoing evaluation. If surgery is indicated, physical exam findings, laboratory analysis of blood and peritoneal fluid and the overall clinical picture will determine prognosis for a positive surgical outcome.
In order to prevent colic from happening there are some precautions you can take:
— Before you leave home for the ride make sure your horse is used to the feed he will be offered at camp. The normal flora in his gut will adjust to whatever feed it is consistently exposed to. Suddenly changing feed at a ride is just asking for trouble.
— If he has been diagnosed with gastric ulcers, or you suspect he has them, have that problem addressed by your local vet. Ulcers should be treated and resolved before you even think about leaving for a competition.
— While on the road, make sure your horse maintains his hydration. Hauling can be an athletic event in itself and horses often arrive at camp behind on water intake before we even ask them to carry us on their backs for a hundred miles. Bring water from home that the horse is used to. Stop frequently during the transport and offer water, and grass if available. Soak the hay to make it less dusty and easier to swallow and provide a bit more water. Although it is a good idea to restrict grain intake while traveling, you can offer mashes frequently with beet pulp and a small amount of grain. Adding a tablespoon or two of sodium chloride (table salt) to a mash will stimulate thirst.
— Once you arrive at camp make sure your horse’s attitude and appetite are normal. Is he stressed? Is he eating, drinking, peeing and pooping? If you have any questions before you start the ride bring them up to the veterinarians as soon as you are aware of them.
— During the ride, monitor water intake, fecal output (ask the riders behind you!), urination and appetite in the vet checks. Are his pulses normal under saddle? Is his cardiac recovery index what you expected? How are his gut sounds? Is he diving into his food or just rearranging it in the feed pan? Remember you can always ask for another exam if you feel your horse is not quite right.
— After the ride you still have a huge responsibility in monitoring your horse’s health. Again, they need to tank up on water and eat to replace energy losses. Did he empty a water bucket or two? Is there poop in his corral? Is he bright and alert? Is he lying down too much? Why does he keep pawing and looking at his sides? Be aware and be ready to ask for help if you need it.
— Trailering home will be yet another challenge so if you have any doubts the night after a ride or the next day, ask one of the vets to take one last look at your horse before you load up.
— Back at home, monitor closely for a few days to be confident that your horse has fully recovered from his long weekend.
In conclusion, there are a few important points to keep in mind. Remember that you know your horse better than anyone and are the first line of defense against colic. Although colic can be fatal if left untreated, most cases resolve with early and appropriate therapy. Colic can be a dynamic problem with the clinical picture changing before your eyes. Understand the causes of colic in endurance horses can be complex and that effective treatment can be challenging but rewarding for the treatment vet, you and especially your horse.