What to do with parent who is borderline abusive?

My 87 yo mother, who lives with us, has mild cognitive impairment which has reached a zenith. She has multiple organ diseases, COPD, CHF to name the most pressing. She has been sick for almost a week....is on antibiotic. She has a very deep cough, and yesterday started to get VERY agitated. It progressed throughout the day. She upset my husband so much he was threatening to leave, making nasty comments about me (not new) and snapping at everyone in the house, even my visiting Aunt, which she would never do normally. She was looking for a specific knife, was not able to find it and was slamming things and drawers. I am a bit nervous to be around not knowing what might set her off. She refused to go to the ER last night after a call to her doc. She was awake the biggest part of the night. This situation is getting dangerous. Any suggestions would be welcome. For reference, she is a very, very non-compliant patient.