Fast pain receptors send signals to the brain at a speed of between 5 and 30 metres per second (via A-delta fibres). So if the pain travels a distance of 1cm,

Fast pain receptors send signals to the brain at a speed of between 5 and 30 metres per second (via A-delta fibres). So if the pain travels a distance of 1cm, it wil reach the brain in between 0.3 and 2 milliseconds. If the killing process lasts any longer than this, it probably generates excruciating pain, albeit briefly.