The Dane kept out a bullet header from Blues striker Garry O'Connor at full stretch from a Sebastian Larsson free-kick in the second half.
It was one of the few moments of concern for Stoke in a game they had the better of, but but both sides will probably be satisfied with a return of four points from their opening three matches of the campaign.
The two teams could not be faulted for effort and commitment in the hot conditions but there was a shortage of quality at times and most of the visitors' best chances came from set pieces.
Birmingham had to be alert in dealing with a series of long Rory Delap throws into the box, while Liam Lawrence caused panic with a couple of decent deliveries into the box.
The home side, who had defeated Portsmouth at St Andrews on Wednesday, came more into the game after the introduction up front of Christian Benitez and Larsson, but Stoke still had most of the best chances to win the game late on.
Birmingham midfielder Lee Bowyer returned to the starting line-up, after completing a three game suspension for his sending off against Preston last season, and replaced Larsson.
Alex McLeish was forced to make two other changes with the injured Gregory Vignal (hip) and Cameron Jerome (ankle) replaced by Stuart Parnaby and Kevin Phillips respectively.
Tony Pulis recalled midfielder Liam Lawrence and striker Ricardo Fuller after resting them for the 4-0 mid-week drubbing at Liverpool with Richard Cresswell and Dean Whitehead dropping down to the substitutes' bench.
Former Sunderland Peter Reid was spotted in the directors' box at St Andrews conferring with Gerry Francis, who is working with Stoke on a consultancy basis. Reid looks likely to fill the assistant manager's role at the Britannia Stadium, although Pulis revealed after the game that talks are still ongoing.
Blues keeper Joe Hart palmed away a cross from Matthew Etherington when under pressure from James Beattie who needed treatment behind the goal after landing awkwardly. Beattie tried to resume but was substituted after 12 minutes by Dave Kitson.
Franck Queudrue brought the home fans to life with the only worthwhile on-target effort from either side in the opening 45 minutes.
He ventured forward to send in a powerful 25-yard drive which Stoke keeper Sorensen was only able to fist into the air.
Stoke had an escape when Glenn Whelan failed to make proper contact with a low James McFadden corner at his near post.
The ball went behind him and rebounded just wide of a surprised Birmingham striker O'Connor.
Delap caused panic in the Birmingham box with one long range throw and Keith Fahey was forced to head over his own bar from almost on his goal-line.
The veteran Phillips got little change up front from Abdoulaye Faye and Birmingham looked one-paced during the first half, missing the running power of Jerome.
McLeish made his first change after 53 minutes with the ineffective Phillips replaced by record signing Benitez as he looked to inject some life into his attack.
Hart was called upon to make his first save after 56 minutes as Fuller got in behind the Blues defence but he failed to make proper contact with his shot and did not seriously test the on loan Manchester City keeper.
Fuller should also have done better when O'Connor misdirected his clearance when trying to deal with an inswinging Etherington free-kick but he headed over from close range.
McLeish brought on Larsson to replace Bowyer just after the hour mark and he immediately made a telling impact.
His powerful free-kick picked out O'Connor whose fierce header forced a fine save out of Sorensen at full stretch away to his right.
Whelan became the first player to be yellow carded after delaying Birmingham from taking a free-kick.
The game was opening up and Kitson was just off target with a glancing header from a Lawrence centre.
Fuller was booked for using his hand to bundle over the line from a Delap throw in the six yard box and it was hard to understand why he protested at the decision to award Birmingham a free-kick.