Because there’s more to handling a sedated horse than just holding a leadrope
1. BE A SMOOTH OPERATOR
Key to a slick operation is preparation: do as much prep as possible before you bring the horse into the room so that you minimise the time he’s standing around. Things to remember:
- Check the QC scan has been run
- Make sure magnet is in correct position
- Check patient details have been entered in the computer
- Ensure the hitching rail is the correct height
- Get sedation, needles and bandages ready
- Make sure both front or both back feet are clean and unshod
- Know where the bucket is!
Make sure the magnet is in the right position before you fetch the horse.
The environment of an MRI room can be a little odd for horses, so it can be a good idea to walk them in ‘sober’ and then sedate once the horse has had a chance to take in his surroundings. Sedating before you bring him in could lead to two things- either the surprise of entering the room could wake him up from the sedation, or he could suddenly notice where he is when the sedation wears off mid-scan. Neither is desirable!
2. MOVE HIS FEET
Remember that a sedated horse’s brain works more slowly, so give him time to respond to your requests. If the horse is reluctant to move then Dan here is illustrating the worst thing to do: you’ll never win in a pulling match, and if the horse shoots forward then he’s only going to run you over!
Dan and Roxy show us how NOT to move a 1 ton shire
Stand by the horse’s head or shoulder and face forwards while asking to walk on. If this doesn’t work, another person can encourage the horse from behind with a tap on the rump. Be careful to stand to the side though, as sedated horses can still kick. If there are no helpers available, unbalance the horse by leading his head to the side, then when he moves his feet you can start to walk forwards.
As always when leading a horse, it’s wise to wear gloves to protect your hands and give a better grip. They can also save your skin if the horse tries to pull back during the scan.
While scanning, the horse must stand square with weight distributed evenly. Think of a perfect dressage halt. A sedated horse’s head will droop so provide a padded chin rest (preferably drool-absorbent) and make sure the poll doesn’t fall to one side. Remember that horses balance on diagonal pairs of feet, so if his near hind is out behind him you’ll have a hard time pickingup his near fore. If he’s too sleepy to pick his feet up for you then moving his head or pulling his tail to the other side will offload the foot and make it easier to lift.
The aim of good positioning is to make sure the target body part is aligned correctly, and also to keep him standing still for longer. A horse that is not standing evenly will at some point want to shift his weight to get more comfortable, creating motion artifacts. Set him up right at the beginning and save yourself from doing repeated pilots when he moves mid-scan.
3. CREATE A GOOD ENVIRONMENT
The purpose of sedating for MRI is to keep the horse as still as possible, but whatever drug is used, you cannot produce a guaranteed level of sedation. Sedatives can only act on the horse’s natural energy levels. The effects of sedation can be prolonged if the horse is kept in a calm and relaxing environment, just as they will rapidly wear off if he gets excited or alarmed. Get good images by keeping him in a calm and comfortable state of mind to maximise the effects of the drugs.
Dan Mountifield, Hallmarq’s trainer, has a top tip for creating the right atmosphere: “Where possible, turn half the lights out during scanning as this helps to prolong sedation. Then you can turn them on at the end to help wake them up”.
A horse might gradually recover from the sedation but still appear quiet and docile. Loud noises or sudden movements can wake these horses up, and they sometimes react explosively. This has caused a few dents in MRI room walls over the years! Let the horse drift off by maintaining a calm environment and keeping voices and activity levels low, with as few people in the room as possible. If the system is in a high-traffic area then it’s a good idea to put up a sign outside the MRI room when a scan’s in progress to remind people to avoid disturbing the horse inside.
4. CONSTANT VIGILANCE!
The horse handler must watch the horse closely throughout the scan for signs that the sedative is wearing off. Too little sedation and the horse might fidget but if levels are too high he may become ataxic (start swaying). Some vets use an intravenous drip to maintain levels during the scan. If this is not used then a catheter is advisable as many horses will move when a needle is inserted.
After a while the sedative will make the horse want to urinate. Lead him out of the room to grass or a stable, or else be ready with the bucket! During longer scans a short leg-stretch outside is often very useful. The horse will be more co-operative when he is comfortable, and a bit of fresh air helps the scan team focus on their job!
If all else fails, do what Livet do and use the MRI Watchdog.