Need help with fluids and electrolytes

Hi, I have an elderly patient who has hypernatremia (sodium=150-high), his blood pressure is normal, and pulse is normal. He also has stage 3 renal disease, his BUN is 40 (high), his GFR is 38(low), and his creatinine is 1.8(high). He also has +4 pitting edema in bilateral lower extremities. He has problems with aspiration and swallowing, so he may not be getting enough water either. He was admitted with pneumonia (from aspiration).

I am SO confused. I know that with kidney disease water is retained. I know that edema is supposed to mean water retention. But according to what I have read, hypernatremia is supposed to lead to water loss. I just don't know what is going on with the fluids in my patient, and it would be great if any of you incredibly smart people out there know what is happening. Any help would be appreciated! Or, if anyone knows of a very detailed reference for electrolytes and fluids that woud be excellent too!

Thanks