After pulling an all-nighter, I find that I fall asleep quite quickly, however, after roughly 2 hours, I always wake up, drenched in sweat, extremely confused (anxious), and with a fast heart rate. I will briefly describe all three symptoms in more detail:
1. I wake up so sweaty that I have to change my blouse, which is completely wet. The bed sheets are also completely wet from sweating.
2. The confusion manifests itself as a sense of anxiety, combined with a rapid movement of thought and an inability to identify a rational cause to it. I feel a sense of impending doom associated with something I was working on during the all-nighter: For example, if during the all-nighter I've worked on a boat design, then I may have the sense of impending doom associated with the irrational idea that the boat is too heavy. (Don't ask too heavy for what, as there is no answer, it's entirely irrational). As I am used to feelings of anxiety, I remain quite calm while this happens - nevertheless, my mind seems to have an impetus of its own, and just continues to associate the sense of impending doom with the irrational idea. Also thoughts seem to move without sense around the irrational idea - all the while I understand that this is irrational, and yet my mind still does it.
3. The tachycardia is typically around 130bpm when I first measure it, immediately upon getting out of bed, but quickly falls to around 110. Then it fluctuates between 90-110 for 30-50mins or so before returning to my normal 75-85. The fluctuations are quite large, for example it would fall to 90 in 20 seconds, and then in another 30 seconds it would increase to 110, and then repeats. It's associated with breathing - especially when I breathe in, the heart seems to start beating much faster. This is associated with an oxygen saturation of 96-98% (measured through pulse oximetry), with an average of 97% most probably. In terms of blood pressure, it is between 135/80-155/95. I've done a series of ECGs in the past, all normal (the ECGs weren't done when this event happened though). Only thing I noticed that could be abnormal was what is a slightly low QT -> around 332 uncorrected, 379 corrected at heart rate 78, or around 322 uncorrected, at heart rate 96. As my heart rate is generally not low enough, especially when I've done my ECGs, it is unclear whether my QT would prolong sufficiently with a reduction in heart rate. Other than these incidents after all-nighters, and a blood pressure which is towards the high side generally (140/80), I've had no problems with my heart.
After the symptoms calm down (roughly 40mins), then I can go back to sleep. I go back to sleep, but find it troubling to fall asleep now. My mind keeps racing through what seems to be incoherent thoughts, and I have vivid and absurd dreams regarding those thoughts. Most of the time, after falling asleep again, I would wake up after another 1hr or so, with similar symptoms outlined in 1-3 but of much lower intensity at least one more time. After the symptoms calm down again, which takes less time the second time around, I again find the same difficulty falling asleep, the same vivid dreams and incoherent thoughts racing through my mind, even though I feel extremely tired. After some time, I can fall asleep, but it's never a deep sleep, and it's relatively light.
So my question is, what causes these symptoms, are they benign, and is it common to experience similar symptoms after an all-nighter? Thanks!