The burning pain in Ellen's arm was due to the rapid application of propofol, a paper-white liquid medication, which the perceptive Dr. Frank had plugged into Ellen's IV the second he heard the c-word. When he saw her reaction, he pushed. The drug, sometimes called "milk of amnesia," stings some patients sharply in the veins, but what it also does is erase your last few minutes.

The Ethics of Erasing a Bad Memory (via Neurophilosophy Blog)