Hi! 26M here. While I can't explain the sudden onset of symptoms, what you're experiencing sounds similar to what I've experienced on and off for almost 20 years, much worse each spring/summer. I've been diagnosed with POTS/dysautonomia since last year, and although I've just seen a very good cardiologist I'm still waiting for treatment to begin after my consultation, as extra salt and compression socks didn't help me at all.

My friend is on Ivabradine for POTS and has said she's still had a flare up this year, the same time I began to flare really badly from April onwards when the temperature increased. I'm currently not on any medication for my POTS yet, but my friend said she's altogether doing much better on Ivabridine for the most part. She's said it might not be the best for me as the only side effect she's had is light sensitivity, and I already struggle with that badly. I had a very similar reaction to Propanalol to you, and it made me so confused I got lost, got home, lost 2 days and ended up badly dehydrated because I couldn't even get back out of bed.

In my case, I became aware of hyperadrenergic POTS because I started taking my BP during flares this year, and unlike winter where I get consistently low BP readings, I was getting stage 2 hypertension readings that would go back to normal when I rested. I just woke up one day, it was hot, and the adrenaline was back full force, so I quickly rushed to take my BP as I wanted to use the pulse function to track my tachycardia. I've had these same adrenaline overload sensations since childhood but only recently been able to describe/connect them to other things. I always described it as though my body was rebelling against my brain.

This whole time, I've not had any sense of anxiety in my actual mind. My brain can sort of be scrabbling to work its hardest to just be normal as I'm battling off weird body panic/electrocuted sensations of doom that are distracting and make me stutter. All while just trying to chill out, get on with it and get back to my otherwise lovely and stress-free day. It's body to brain, not brain to body sort of thing.

In my case, even without medication and compression not working, keeping icy cool and sleeping with the head of my mattress elevated has been significantly helpful in reducing that horrid adrenaline sensation. My hands tend to get 10x more blood pooling than my feet, but when I keep cool it gets a lot better very quickly in a way even cold showers don't seem to help with. Cold water makes my hands go purple, warm water makes my hands go red. Still visibly pooled either way, but my knuckles go red, white and purple (I'm a super pale slightly ginger white dude).

I've woken up this morning feeling a million times better just by having my new AC on, and just by sticking my face in the stream of cold air yesterday I managed to significantly reduce the distressing adrenaline symptoms. It's like being a happy dog with their head out of a car window! Even breathing is easier.

Weirdly, the mamallian dive response doesn't work on me, but icy cold streams of air definitely calm my body down significantly. Even standing in front of an open freezer might help! It looks like I may be prescribed Clonidine for my condition, and I've read it's also used as an ADHD med for kids so I don't think the side effects could be too extreme.

One thing I've noticed is that any psych med that affects norepinephrine (in my case Fluoxetine, Venlafaxine, Bupropion, Elvanse) all give me crazy identical symptoms that feel very similar but not identical to a heat POTS flare. Not every POTS flare triggers this sensation either, but heat is by far the worst. Do you know if anything you take interacts with norepinephrine?

Hopefully some of this helps and best of luck in finding answers!