This is from Tayan's web site about CD " Giving too many fluids or too soon may also increase the risk of
overhydration. This is a particular risk for cats with
heart problems. Therefore it is best not to begin fluids until the advantages are likely to outweigh the disadvantages "
Dr Katherine James of the
Veterinary Information Network believes that this tends to happen and that most CKD cats will benefit from subcutaneous therapy once
creatinine levels are consistently over 3.5-4.0 mg/dl (USA) or 300-350 µmol/l (international). This equates to high Stage 3 of the
IRIS staging system. If your vet thinks your cat's CKD is less advanced than this, and your cat does not appear
dehydrated, then it is probably better to hold off on sub-Qs for the moment. Giving more than is needed to maintain hydration is a strain on the kidneys can make a cat feel uncomfortable. "
Sometimes a CKD cat may develop fluid retention or fluid build-up. This may be a sign of worsening kidney values or of
heart problems, but in many cases it is actually a sign of overhydration from subcutaneous fluids .
https://felinecrf.org/symptoms_regulation_body_fluid.htm#overhydration
You mentioned Bella had fast breathing & open mouth. This was also mentioned on Tanya's site about over hydration.
Ravan has not had any Ringers yet because his Creatine is at 2.0 the last time he was checked. Because Alice & him appear to have runny eyes & sneezing I'm going to start giving them ringers twice a week.
Hope this information helps.