Do iv fluid treatments cause swelling?

After a lengthy IV, some bruising is not uncommon. However, if the swelling is larger than a bruise, or not discolored like a bruise, I'd wonder if the needle was properly placed, or if the caregiver accidentally missed or went through the vein and actually injected something subcutaneously by accident. If it was normal sterile saline, lactate of ringers, D5W or any sterile hydrating liquid, this shouldn't pose a problem -- but call anyway. However, some meds must be IV injected and, if this is the case, you need to call that vet back and get this fixed. In any case, you need to call the vet who did the original IV and ask what's what. I would add that a vet call made to correct the vet's aim should be on the house.