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DrMelJ, Horse Veterinarian
Category: Horse
Satisfied Customers: 850
Experience:  experience in racetrack medicine and general practice; owned and ridden horses throughout life.
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I am looking for advice on blood sampling. On thursday at

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I am looking for advice on blood sampling. On thursday at 12.00 midday I had my horse blood sampled to test for cushings disease. The vet took the blood from the neck into a vacuumed test tube attached to the needle. I watched and noticed that the blood was not the usual dark colour as it came into the test tube but didnt really know if that was an issue at the time. I have seen blood administered from the vein on numerous occasions but this was not the same colour although it may have been once it cleared but I want to mention this as I am concerned it might be arterial.
Six hours later, I went to feed my horse, I walked with him carrying his rug and feed and he walked nicely alongside me. He was rugged up and he had his head in the bucket. I left the paddock, but a few minutes after leaving him he was neighing frantically and started bolting around the field neighing in some distress. It was not unusual behaviour for him as he sometimes does bolt round the field so I wasnt unduly concerned at that moment but it escalated and the neighing became more intense and when my horse finally stopped he fell against the gate and rolled on the floor, when he got up he was staggering around and shortly after died.
My horse is a retired race horse aged 21 years and was not fit. I could accept that maybe it was natural causes, but because the Vet had taken a blood sample from him only 6 hours before, and I feel that I need more information as currently I beleive this could have been the cause.
My questions are...
Could the blood sampling have caused an air embolism ?
Could such a small amount of air if this was the problem, cause a heart attack ?
How does the six hours fit in with this? I would like to know how long approximately it would take for a problem to occur from the time of sampling please.
I decided not to have a post mortem due to costs as his insurance would not cover the costs.
Thank you for any advice you can offer.

Thank you for the question. I am so very sorry to hear about the tragic loss of your horse. I hope I can give you some insight. ....

I believe it is highly doubtful that the vet drawing blood that day had anything to do with what happened.

1. If he was using a vacutainer tube, there is no way he could have injected air into a vein or artery. The vacutainers are set up as a vacuum (hence the name) and therefore only draw the blood out. It would have required a syringe with air in it for him to push air into a blood vessel.

2. The large amount of time between the blood draw and his tragic death. Even if there had been an embolus would have caused a problem very rapidly....within minutes.

Without a necropsy it is impossible to tell exactly what happened to your horse, here are some ideas based on my years of experience in practice...

1. A sudden and severe colic....yes these can happen. I have seen horses go from normal, to incredibly painful and distressed to dying within minutes if a part of their bowel becomes severely entrapped or obstructed and then ruptures. Kind of like a dog with a severe gastric bloat and volvulus.....Usually it takes much longer but their are severe cases with a rapid progression

2. A chordea tendinae rupture in the heart. Horses dont have heart attacks in the way people do......but older horses (especially if they have a known heart murmur) can have a weakened valve and sometimes suddenly, one of the pieces of tissue that anchors a valve will break causing a complete disruption of normal blood flow in the heart. This can kill them very quickly.

I am very sorry once again for the tragedy you endured with your horse. I hope this gives you some insight. Take care.

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