It’s has been well established that Bariatric patients can develop orthostatic Intolerance post Bariatric surgery. It is a complication of the autonomic nervous system. Just google Orthostatic intolerance after Bariatric surgery and you will find page after page of articles documenting this syndrome. All the symptoms you mention are there. Autonomic dysfunction is not well understood and many physicians are unaware. I have had this syndrome for 4 years and I have not had Bariatric surgery yet. I ran across all this information while looking for research about my illness. I get shaky, sweaty, nauseated and dizzy with brain fog. I have collapsed numerous times but have never lost consciousness. If I lie where I collapse lift my leg up in the air to allow the blood to return from my legs to my upper body I can get up and be alright for a little while. I specifically cannot stand in place. I must be walking or the dizzy collapse feelings hits me immediately. All my symptoms resolve when I lie down. I understand this has been noted to be a common post op complication of Bariatric procedures. Please take the time to do a little research. You may just be able to tell your physician what is wrong with you. I wish you luck. There is no cure but there are treatments to improve it. I was diagnosed at the Mayo Clinic. This is a neurological condition and I was in the Emergency room 27 times before a cardiologist picked up up all this was happening when upright. I was fine lying down. I am a registered nurse and I was absolutely scared to death when I was told over and over you are alright, your test are normal. I did not feel normal and it was not anxiety/ panic attacks as many suggested. I had become very angry with the lack of concern for my symptoms. I was dizzy with a racing heart and all the symptoms you mentioned and more. I am so thankful that I ran across a physician that was knowledgeable of the condition and knew I needed expert care. I struggle, and was unfortunately completely disabled 7 months after my symptoms first appeared. I am so debilitated physically that I have gained 60 pounds and am pre diabetic. I am currently working towards the gastric sleeve. I am afraid it may worsen my condition but I have a glimmer of hope it may improve my situation somewhat.
I forgot to mention that I experienced the same situation when showering. The Mayo Clinic physician explained because of the blood shift and pooling to the legs and lower abdomen upon standing, that the hot water in the shower acts as a vasodialator which worsens the blood return to the upper body. The dizziness is hypo perfusion of blood to the head. I get short of breath, with chest discomfort and dizzy. The heart begins to pump hard and fast to return blood to the upper body.