Blimey, you poor soul! Did the doc say what had caused the kidney failure ?
Have you ever had a head MRI, I ask this because, I wonder what the state of your cerebellum (lower part of hind-brain) is. I wonder if it is blocking CSF flow between the head and the spine. This could build up pressure in the head making it more difficult for the heart to deliver oxygen to the brain – hence the high blood pressure (necessary to get the oxygen to your brain), or tachycardia when this mechanism was pharmacologically removed, this could cause lightheadedness and symptoms caused by raised demand on the heart, which could be palpitation, chest tightness and that sort of thing.
It might explain why you operate better lying down, as you no longer have to compete with gravity.
I am not a doctor but I am keenly interested in nutrition because I think it’s the way forwards for many of us. I would agree with the salt but also want to suggest Multivitamins, Magnesium (epsom salt baths, very beneficial) etc but I’m not sure what you can have with your kidney condition, can you enlighten me what is allowed and what is not, nutritionally? I have a vague recollection of restricted potassium, which is a shame because it sounds like you need some.
Let me know and I’ll have a think on it.