I have a horse that's recovering from a stone bruise so I've been checking his digital pulses quite frequently. Obsessively is probably the best adjective. 1-One thing I've noticed is that even if the hoof is stone cold (10F here at the moment), if I check for a pulse the first time and feel nothing, if I go back subsequent times within a short time frame a palpable pulse will develop. 2-I've also been a bit baffled to find that on the injured hoof, if I feel a strong pulse the first time I check then go back five minutes later, sometimes it will have all but disappeared. What could be the explanation for both scenarios? I would think that if there were inflammation, the pulse would be fairly consistent. In both instances the horse is "cold"- as in not having been exercised.
You need to look at A V A 'S, Arteriovenous Anastomoses, these regulate the passage of blood through the foot, If you have increased pulse then you have a raise in blood pressure, if that is accompanied by heat then that raise in blood pressure is in response to inflammatory conditions. If the foot is cold then its just a raise in blood pressure, not inflammation. It becomes more problematic when laminitis is suspected. http://www.laminitisresearch.org/downloads/chrispollitt_PolllittBookChapter.pdf The above link does not suggest that you have a lamintic horse, but is quite detailed about the blood flow through the hoof.
Something you might find useful in this situation is a temperature probe. It reads the surface temperature in a pinpoint area and it has a laser pointer so show where it is taking reading. They are inexpensive and can usually be purchased at auto parts discount stores. I use one for locating inflammation in the lower limb and hoof bruises and abscesses. Usually the "sore spot" will be 5 to 7 degrees warmer than the surrounding area. You can also compare the temperature between two different feet. http://www.tooldesk.com/automotive/RTKMT4-Infrared-Raytek-MT4-Thermometer-wlaser-sight.aspx http://www.amazon.com/Raytek-MT4-Non-Contact-Thermometer-Sighting/dp/B0002198GY I wouldn't pay over $40 for one of these units. I got mine at Pep Boys for $35 over 10 years ago. The laser pointer is also handy for entertaining barn cats . . .
Just a guess. Healed enough to be comfortable unless he/she steps on a rock and makes it sting for a few minutes. Take that as what it is - a WAG (wild ass guess).
@David- Thank you so much for the link! Blood pressure might explain why the pulse is strong while he's eating a grain meal vs. when he's eating hay. I would think grain is much more exciting. Isn't there also some phenomenon where in cold weather the horse will periodically "flush" a leg with blood to warm it up? My google and vocabulary skills are failing me on that one. Would that explain an intermittent pulse as well? I don't know, something like the normal blood flow and a certain level of inflammation don't show a pulse, but send some extra blood to the region and then the pulse appears? @Tom- Sounds like a fun and useful tool to have! And thanks for the heads up on the $$$, I see that same model going for a lot more elsewhere. @Jack- Your WAG is better than mine! I worry about this guy because he's so stoic. DraftQHTBX. He's challenging for me to ride because he's so sensitive and holds me accountable for any and all of my riding faults, but when it comes to pain he's... numb. I've been obsessive about checking the pulse and heat because I feel it gives me a better picture of what's going on than how he's moving. (I also own an opposite horse, one who is forgiving of my riding errors, but will feign death over any little scrape or bump.)
Isn't there also some phenomenon where in cold weather the horse will periodically "flush" a leg with blood to warm it up? My google and vocabulary skills are failing me on that one. Would that explain an intermittent pulse as well? I don't know, something like the normal blood flow and a certain level of inflammation don't show a pulse, but send some extra blood to the region and then the pulse appears? That would be the AVA's, don't know about pulse, but here's what happens with temps. Sorry can't get an upload, but Dr Pollit embeded thermocouples in the dorsal wall of horses in Norway and I have a graph of three days of temperatures. The ambient temp was continually below freezing. Hoof wall temp varied from a few degrees Celsius (almost freezing) to only a few degrees below body temp. Feet temps vary drastically as the AVA open and close.
Thanks Jack! Found it, the cold stuff starts at page 14: http://www.itarget.com.br/newclients/abraveq2012/down/2007/Horsesfootinsidestory.pdf I just don't know. I'd love to put this horse back into regular work because to me he looks fine, but the warmth and pulse bother me. If it were my other horse he'd be lying in his stall waving the hoof in the air and sobbing. Does it feel relatively warm because everything else is frozen solid? Am I catching it during a warm up phase, because sometimes it is cold? I have the vet coming back this week to get some other eyes on the current situation.
if you don't want to buy the laser temp thing and your worried about a hot foot. Take a wet sponge, wipe both feet and if the wetness evaporates faster on one, more than the other or faster on one part of the hoof vs the rest of that hoof, then you MIGHT have a problem. 200yr old technology
Thanks for the link, Cheryl. I'd lost it - had the graph on my computer but not the whole pdf. Don't be too surprised if this is new stuff to the vet. They have to keep up with the entire horse as well as other species. Not just the feet. i.e. I've spoken to several vets about negative palmar angle. Most have heard of it, but haven't worked with one, don't have much advice. Might be an interesting research project - bounding pulse vs temperature changes. I'd guess that with the AVA's open, the temps increasing there would be a reduced pulse, but that's still a WAG. I'd guess it's time to put your horse back to work, but that's a vet decision. Note on the temp graph, the morning low temps. I'm guessing that's feeding time when the blood is shunted to the stomach rather than the feet. Out cross country skiing, I get cold hands and feet right after I eat.
Good stuff Jack. Its refreshing that a horse owner can come on here and be enlightened, I wish it happened more often.
I finally had a cup of tea and time to sit down to try to absorb David's link. "Pulsation of the digital arteries is almost certainly a sign that arteriovenous shunting is occuring." and from the other link: "Frequent warming of the foot no matter what the ambient temperature appears to be a feature of normal foot physiology perhaps to ensure that metabolism and growth are never compromised." So maybe the healing hoof would perhaps cycle more frequently than the others, considering AVA shunting due to cold weather is not linked between feet? Jack, the horses in the study were fed ad lib hay, so no distinct meals.
Cheryl, just interested in a bit of history about your horse, How old is it, what do you use it for and is this the first time its been lame? Is he shod or unshod? This site is very easy to attach photos to If you have any views of his feet.
I don't have any current views of his feet. He is not shod. He's 8, a Quarterhorse/Draft/TB cross (a PMU horse, so no one intentionally bred for that!), and has never been lame. I was on him when it happened- he had gone beautifully under saddle in the ring and I had him on a long rein in a stretchy walk through the woods on the way home when he tripped over a branch. I hadn't even seen the branch under the leaves, it had been a while since I used that trail. Well, the trail is new and I had recently pruned out some small trees beside it. As close to the ground as was possible. When he tripped and caught himself he came down on one of the little stumps. Instantly head bob lame, I got off, unwrapped him, checked everything down his legs, checked for puncture... he was almost totally sound by the time we got home. A slight amount of heat and tiny pulse. He looked fine so I rode him the next day and he felt 98% sound, just a hair more "crooked" than normal. I didn't think too much of it, as I've never had much of a problem healing up a bruise. Two days later, after being fine in the AM I came home to find him dead lame at the walk so the vet was called, but within 3 hours he was back to being almost 100% sound. We ran some bute through him, gave him some stall rest. To watch him run around in the pasture he looks fine. I apologize for the dark as it's been really cloudy here, but I hopped on to try to see how he felt and see how he was moving. I couldn't get him to go as fabulously as I know he can go, but here is what I got. View: http://youtu.be/6GvHu3VkeF4 If you think that's hideous as far as movement goes, this is where we started. *cough* View: http://youtu.be/-Y4WIXqkbWs I guess you could say I do dressage with him. I don't expect him to ever get beyond the lower levels, he's not built for it and I don't require that he even try. This pic isn't as old as that second video, but here's a moment in time. http://img.photobucket.com/albums/v328/CheryG/WP_000076.jpg (wow do I miss those palm trees! LOL!)
