This whole situation is in the past, but I'm still looking for answers.
I'm interested in knowing why giving a 12 y/o, indoor only cat 100 mL of Sub-Q fluids twice a week would cause him to become sluggish and stop playing (his playing involved running around the house). About a month prior, all blood work and urinary results were normal. An x-ray was done at my request just to confirm everything was ok since there was a history of stones, and the x-ray looked good. The vet did say my cat had a grade 2 (out of 6) heart murmur. In the past, the vets (two of them) had always diagnosed it as either a grade 2 or sometimes a grade 3. They both said further testing wasn't necessary at that time.

The fluids were given maybe a total of six times to try to flush a stone out of the ureter (the tube that connects the kidney to the bladder). The sluggishness started after about the second or third time. I complained so much about the sluggishness that the vet relunctantly told me to stop giving the fluids. After my cat stopped getting fluids, his sluggishness improved only a little. He would play, but if his playing involved running, he would become tired very easily and stop. His appetite and thirst seemed normal. He also seemed to be using the litterbox normally, with no obvious increase or decrease in urine production.
A little over three months later, my cat was taken to the vet for lethargy and loss of appetite. X-rays were taken that showed fluid around the heart. I was immediately sent to the internal medicine vet who did an ultrasound. A diagnosis of right-sided heart failure was made. Based on the poor to grave prognosis from the internal medicine vet and the regular vet, as well as my own gut instincts, I chose to euthanize my cat. After doing weeks of researching these medical problems, I still stand by my decision.
Did the Sub-Q fluids cause the heart failure? I know it's possible my cat could have had some sort of undiagnosed heart problem (like cardiomyopathy), but he was acting perfectly normal until he started receiving the fluids. So, even if he did have an undiagnosed heart problem, it sounds like the fluids still caused the actual heart failure.
Does anyone have any thoughts on this? I'm having a great deal of difficulty finding anything about Sub-Q fluids causing heart failure. The only website I can find that discusses this is one that is created by cat owners who don't seem to have any veterinary training. I tried to ask the internal medicine vet about what caused the heart failure, but was only given the runaround, which I'm sure they do for legal reasons. He did say the heart murmur should have had further testing years ago.
MJ,
A stable, low-grade heart murmur is not indicative of any particular cardiovascular condition, and, in and of itself, does not contrindicate sub-cu fluids, though increased caution and observation is indicated, along with close monitoring for any changes in the level or nature of the murmur.

I'd guess they were using Ringer's Lactate. It is certainly possible that it could exacerbate an existing congestive cardiac condition while being administered (1), but it is unlikely to cause one. Since congestive heart failure is treated with, among other things, diuretics, an excess of fluid volume could have increased the congestion, and due to increased pressure, accelerated muscle damge due to constriction of the blood supply. That is particularly true if kidney function was impaired and fluid clearance decreased. But whether that did or did not happen can't be definatively determined.
Of more importance to the behavior changes, what was the outcome of the stone? An obstructed ureter can cause kidney pain, and it can be second only to giving birth. One of my sisters had one and she will tell you in a heartbeat the pain was only slightly less than having her first child, and worse than having the second and third.
You also didn't mention the breed, some are more prone to congestive heart problems than others.
If the cat was born before the late 80's, your cat's cardiomyopathy could have been exacerbated by a lack of taurine in the diet. Taruine is an amino acid that carnivores cannot synthesize as omnivores do. They must get it from their diet, and if that diet does not contain organ meat, or is not supplemented with taurine, it can lead to vision problems progressing to permanent blindness, and condition called feline dialated cardiomyopathy, but that is reversible with taurine supplementation.

All commercial cat foods that have the AAFCO approval label are required to have taurine added (I think that happened in the late 80's). If you were feeding a cat food with taurine added (it will apper near the end of the ingredients list), taurine shouldn't be a factor. However, non-certified foods and homemade foods may be deficient in taurine. Dog food is certainly inadequate, as dogs are omnivores and can synthesize taurine.

All this said, I have to agree with the IMV that the persistent murmur would have better been investigated earlier. Heart murmurs are not uncommon in cats under 18 months old, but they typically disappear as growth and development complete. Since the murmur was pre-existing, the defect was probably congenital (present at birth). Whether the fluid, or a taurine deficiency, were contributory, or to what degree, cannot be known. Nor can it be known whether medication would have mitigated the normal progression of the defect or disease. My sense is that if the IMV thought vasodialators, beta blockers, angiostatins, or diuretics would have been helpful at that point, he would have said so.
Congestive heart failure can be caused by many factors, including coronary artery disease, heart attack, high blood pressure, heart valve disease, heart muscle disease, infections of the heart valves or muscle, or congenital defects of the cardiovascular sytem or the heart itself. Most of the above have a remarkable onset, that is, suddenly appear. Obviously, congenital issues are present from birth.
We've had 19 cats over the last 50 years (we will take in cats, usually older, with diseases or conditions that require a 'nursing' level of attention), and have had to make your decision a number of times. When that desision must be made, it isn't about us, its about the cat. It isn't about past events, its about future quality of life, or the lack thereof. I commend you for trying to learn from the past, it is the only way the past can positively contribute to the betterment of the future. But, IMO, your decision was the correct one, and certainly the one I'd have made under those circumstances.
Allan
(1} Relationshhipof hydration and heart physiology may be found at http://www3.interscience.wiley.com/journal/119819256/abstract?CRETRY=1&SRETRY=0

One asks, many answer, all learn Plato, on the 'Forum
True civility is when every one gives to every other one every right that they claim for themselves.