Bizarre and terrifying derealization experience--panic attack?

I had the most terrifying experience a couple of days ago which landed me in the ER. I have anxiety (GAD) but I've never had a panic attack before. I'm wondering if this is what I experienced?

Basically, I woke up that morning feeling fine. Went for a run around noon and sort of putzed around the house for a few hours. I laid down at around 6:00 pm to watch a soccer game when all of a sudden I was hit with this sensation of being sort of "out of it". I don't know how to describe it. My ears started ringing very loudly, my legs felt weak and I had a burning sensation in my feet, I felt nauseous, I was hit with vertigo, and my vision seemed affected as well (not as in blurred vision, more as in distorted vision--like looking down at my legs they seemed 10 feet away).

I knew where I was but I had this overwhelming fear that "something is wrong with me". I called my brother who has had panic attacks. I remember talking to him and answering him, but it felt like I had to concentrate very hard to stay focused on what he was saying and how to respond.

I got my husband from outside and he tried helping me to calm down. But the sensation just got worse. I thought I might have low blood sugar or something so had him get me some juice, but that didn't help. Tried to wait it out but the sensation just got worse and I felt like I was dying. I told my husband "I really feel like I'm going to die".

Long story short we went to the ER and they did an EKG, CAT Scan, CT Scan with contrast, and did some blood work. All tests were normal though I was very slightly dehydrated. I finally started feeling better around 10 pm, so about 4 hours after the whole thing started.

I still have ear ringing but it's getting a bit better with time. I still have the weird sensation of burning feet (not painful, just annoying).

Anyone else ever have a panic attack that manifested as a depersonalization/derealization type sensation?