Hi. I am 34, active and healthy, and I had arthroscopic knee surgery 6 days ago to remove a gangleon cyst. I am doing okay with the knee, but yesterday I started having other concerning symptoms. I fainted twice, and each time since then that when I sit upright, stand, or walk around, after about 5 minutes I get a wave a nausea, sweats, light-headed, and the feeling like I am going to vomit and/or pass out. I have been eating and drinking well, have no other health problems or medical history, and haven't taken any medications in over 48 hours. Any advice??