Noted the history about your 100 year old Mother having hypertension
, low potassium, possible kidney infection
with back pain in the same area, started on Sulfamethazole and Trimethoprine combination, development of symptoms and signs realted to some complications as you have mentioned.
Development of purple patches on skin or mouth shortness of breath
and so on.
Yes, you should take her to the ER asap as waiting can cause more problems.
This may be reaction to medications or development of septicemia due to urinary tract infection
that can be diagnosed by the following ways only:
Clinical evaluation and examination by a Doctor and investigations of blood and urine along with ultrasonography
of abdomen for kidneys.
Stop giving any medicines till seen by a Doctor.
Hope I have answered your query. Let me know if I can assist you further.
Dr. T Chandrakant, ENT & General Surgeon