This is exactly what happens to me. I get in a group conversation and I start to speed up, I can feel it trigger a hypo-mania, and off I go. Sometimes it later is embarassing to me because I completely take over the conversation. At the time I realize it a little by the way people are looking at me, but I can't slow down, or shut up. Later I usually regret it. It takes me 3 to 4 hours to slow down afterwords.