Chicago won its second straight, improving to 2-0 under new head coach Denis Savard, who replaced Trent Yawney on Monday. Jeff Hamilton, Tony Salmelainen, Mikael Holmqvist and Martin Lapointe also scored for the Blackhawks, who dealt the Blues their fourth consecutive loss. Holmqvist and Lapointe scored empty-net goals in the final minute.
Khabibulin lost a bid for his first shutout as a Blackhawk - and first in regular-season play since March 1, 2004, while with Tampa Bay - when Blues defenceman Dennis Wideman scored a power-play goal 34 seconds into the third period.
St. Louis' Bill Guerin scored late in the third.
Blues starting goalie Curtis Sanford left the game just 6:15 in after suffering an leg injury that led to the game's opening goal - by Hamilton - on Chicago's third shot.
Manny Legace took over in nets, allowing two goals on 27 shots.
Sanford crumpled to the ice just over six minutes into the first period as he moved to block Patrick Sharp's shot, which sailed just wide of the left post. Seconds later, Hamilton picked up the loose rebound and tucked it into the unguarded net to give Chicago a 1-0 lead.
Sanford had to be helped from the ice.
Ruutu gave Chicago a 2-0 lead just over a minute later, scoring on the first shot against Legace. He connected through goalmouth traffic on a high wrist shot from the left circle.
Khabibulin stopped Radek Dvorak with a glove save on a breakaway at 5:50 of the second.
Salmelainen scored his second NHL goal - and second in two games - with 7:46 left in the second to extend Chicago's lead to 3-0. He beat Legace on a screened shot from the slot after taking a perfect feed from Duncan Keith in right corner.
Wideman cut it to 3-1 just 34 seconds into the third, beating Khabibulin on a screened shot from the left point.
Guerin knocked in a loose rebound of Keith Tkachuk's shot with 7:20 left to trim it to 3-2.
Khabibulin stopped Tkachuk from the edge of the crease, but Guerin drove to the net and muscled in the rebound.
Holmqvist scored into an empty net with 46 seconds left to make it 4-2, and LaPointe added another empty-netter with three seconds remaining.