The walk from the dressing room probably took longer than the time defender Rashed Al Hooti from Bahrein was on the pitch.
Australian referee Peter Green send him off after about 40 seconds (but some media do have different watches: 34, 39, 40, 43, 49 were mentioned) in the World Cup 2014 qualification match against Iran. This is probably the fastest red card in an international country match.
But it definately is the fastest red card ever. Have you ever seen Preston Edwards (Ebbsfleet United) in the match versus Farnborough? Take a look at the video below where referee Neil Hair sends of the goalie after ten seconds.
Ebbsfleet United v. Farnborough (5.2.11) from MyFootballClub on Vimeo.