i'm in my last semester of nursing school and can't for the life of me understand what the dr. was telling me when i took my son to the er this morning. he is 18 and has been experiencing sinus arrythmias, orthostatic hypotenstion, severe headaces and also has a heart murmur. the one thing i don't quite get is he has been having what he calls blackout spells. he doesn't black completely out he says for about 10 seconds he sees nothing but black and then it goes away. the dr. gave him iv fluids, did a cat scan and all his blood tests were normal?? does anyone know what could cause this? she thinks this may have something to do with "dehydration"?? i'm not so sure. :stone she did refer him to a cardiac specialist and a neurologist but says everything seems to look ok. can anyone give me any advise? it would be greatly appreciated.