Often, when cats with CRF are first brought to a veterinarian, the condition has caused serious, life-threatening dehydration. In these cases, the BUN and creatinine may have increased dramatically. Also, a cat that has been successfully treated for CRF for some time may crash, resulting in a spike of BUN and creatinine. IV fluids provide immediate hydration and may be administered by your vet for several days at a time.
A course of IV fluid therapy can be stressful for cats but when a CRF patient is in such a critical state, it is the best treatment to re-hydrate the cat and lower the levels of toxins enough for the caregiver to continue home care with sub-Q fluids.
While the IV fluids are being administered, the patient's blood values and other vital signs will be monitored periodically. In most cases, the values will begin to correct themselves within a day. Your vet will prescribe IV fluids at a volume and for a duration tailored to the cat's size and BUN and creatinine values. Once the cat is stabilized, IV fluids have to be slowly reduced rather than stopped abruptly. A three to five day stay at the hospital is not uncommon.
IV fluids may cause an imbalance in blood electrolytes which can result in some temporary side effects like listlessness and disorientation. After IV fluids have been administered, it may take from several hours to a day or more to restore the blood electrolyte balance that has been upset.
IV Fluids and the Heart
In those instances where the patient has both CRF and a history of heart problems, IV fluids must be prescribed very judiciously as the increased blood volume caused by the fluids can severely stress and damage the patient's heart. Some heart conditions are discovered when the cat is on IV fluids. This happened to our cat, Duncan, while getting IV fluids for CRF. He developed respiratory distress and an echocardiogram revealed restrictive cardiomyopathy.