Good Morning and welcome to Just answer. I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
I am so so sorry for your loss! I know this must have been extremely traumatic for you.....
Calcium is required not only for growing bones but also an integral part of Muscle contraction and nerve conduction. From what you deswcribe, it appears that this amount of calcium given IV may have been too much or too fast for the Clydesdale causing an interference with the nerve conduction to teh heart musckle and/or with the "calcium pump" involved in heart muscle contraction, stopping the heart and causing death....thecondition that your guy was suffering from was not fatal but thsi meidcation, when given too fast, can be fatal. It is not the fault of your vet...we can only do what we think is best and sometimes this is too much.
Does that make sense to you?
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please Reply so I can clarify for you
Sincerely, Dr. Loretta