Ive never rexperienced anything like it. It happens extremely fast. Dr injected into the IV and instantaneously every muscle in my body contracted (at least that's what it felt like), I lost my vision temporarily although my eyes were still open. Similarly I couldn't hear anything either. I was filled with an extreme feeling of...rushing...adrenaline... Really hard to describe. I felt my heart give one last big THUMP and then stop.
And suddenly, my heart started again. My vision and hearing restored, I was back in the ER surrounded by Dr and nurses and techs. Breathing hard, somewhat confused and experiencing a little twinge in my back from the contractions.
The whole experience took maybe 3-4 seconds. It felt like minutes.