I would say no, I wouldn't change any of his medications without consulting a doctor. I can't emphasize enough that you need a doctor's input in a situation like this. It's now Sunday evening, so hopefully your father's doctor will be available tomorrow, and hopefully he will make it okay until then.
I'm kind of shocked to hear that there is a medical doctor who doesn't have anybody on call when he's unavailable. I thought that was standard nowadays -- that anybody practicing clinical medicine is obligated to make arrangements for an on-call doctor. Even solo practitioners have to do that. They usually share call with a clinic or with one or more other solo docs.
The danger in decreasing your dad's diuretic is that fluid could build up on his lungs and cause him to have trouble breathing, and he could go into crisis. He's on the diuretic because his heart can't move enough fluid, and that won't change. Were he clearly dehydrated already, that would be one thing, but your post indicates you are concerned only that he might get dehydrated as time goes on.
I understand the concern about taking your father to the ER, but if his overall condition gets any worse, or if your sister has too much difficulty keeping him cleaned up, then the ER might be your only option. When you do talk to the doctor, I would get his input on what you should do in a future situation such as this. In my opinion, your father is too frail for you not to have a doctor that you can call 24/7. Good luck.
Thank you! Yes, I'm truly shocked too by the poor quality of medical care available in North Las Vegas. My sister had a very hard time finding ANY doctors who would take on a new Medicare patient when we first moved him out there 6 or 7 months ago from his solo home in Florida. Today she tried both the doctors she did finally find (one cardiologist and one primary care) and neither one had anyone on-call, just a recorded message saying what their normal office hours were and no way to contact them outside of office hours. We were very worried about exposing him to even more illnesses during a long wait in the ER and were planning to just watch closely until tomorrow, but he did get a little worse and she did have to call 911. He can only walk a very short way when he's well, and in his current condition he couldn't walk at all and she couldn't lift him to get him into his wheelchair or into the car to drive him. We hoped that if he arrived by ambulance like that he would at least not have a long wait to be seen once there, but no such luck. It was hours anyway, but at least he didn't have to sit in a waiting room chair the whole time like on other ER visits. We would love to have a doctor we could reach 24/7 for him, but haven't been able to find anyone like that in North Las Vegas. I'm going to keep my fingers crossed that my sister will encounter a physician via the hospital now who can provide better care. They've admitted him for an IV antibiotic and an overnight stay. We may have to try to move him again, to my place in California, where there are many excellent doctors available, but I'm not sure if he'd survive another move. Thanks for your help.
In most cases like this, Hospice is recommended. Sometimes people don't want the end of life help, but in my experience with four loved ones, they were able to complete their lives with class and dignity. I have Congestive Heart Failure and have made sure my family will empower Hospice to keep me comfortable when my time comes. I learned this from my father who was what could be called a country doctor, and felt strongly people should leave the world as painless as possible. Blessings.
I will add to Flycaster's comments, sometimes a hospice service can provide in-home services. People tend to think of hospice as "a place where you go to die," but in my own state of Arkansas, it's almost all in-home services. If there is a hospice in your sister's area, maybe using them would provide a way for your father not to have to move again.