Sissoko swiftly discarded his protective goggles, ordered by the doctor after his recent eye injury, as Liverpool charged forward to plunder goals at will against opponents whose defending bordered on the suicidal. Liverpool were good, particularly Steven Gerrard and Peter Crouch, but Birmingham were utterly dreadful.
So frustrated did the home fans become that two incensed supporters ran on to the pitch. The first, at 3-0, tried to throw his season-ticket at Bruce. Fortunately for Birmingham's manager, his stewards were quicker than his centre-halves had been in averting danger. The second pitch invader, at 6-0, was also stopped in his tracks.
Already hamstrung by nine injuries, Bruce cannot be blamed for the individual errors and lack of concentration by his centre backs. Why Martin Taylor did not get closer to Sami Hyypia for the 55th-second goal that triggered the rout will be the first question Bruce asks in today's painful inquest.
Taylor's display was deemed so disappointing that he was removed at the interval. For a former centre-half of Bruce's noted calibre, such defending was unforgiveable. He eventually introduced his son Alex, and must have been tempted to send himself on to bring some organisation, talking and leadership to the back-line.
The pressure on Bruce will inevitably intensify, particularly as he faces an awkward struggle against relegation with no silver lining like a Cup run and no respite in sight. Next up for Blues in the Premiership are Manchester United, Chelsea and Bolton Wanderers, which is not a fixture list but a firing squad.
Yet Bruce, who has never hidden as player or manager, came out and faced the music last night, a dignified presence in defeat, and a contrast to Alan Pardew, who refused to talk after West Ham United reached the semi-finals 24 hours earlier. If Bruce manages to lead Birmingham to safety, many neutrals will applaud his efforts.
Birmingham's supporters appear largely behind him, aware of the side's limitations in the absence of Matthew Upson, Muzzy Izzet, Chris Sutton, and Emile Heskey. Blues certainly lacked a spine last night.
The observation by Birmingham's president, David Sullivan, that this "has been the most depressing season since I joined" were sentiments echoed by the many fans wondering when the agony will end.
Ecstacy characterised Liverpool's mood as they made it 15 goals in three games. The first of their magnificent seven came when Sissoko flicked on Gerrard's free-kick and Hyypia nipped in to head home.
Within three minutes, Sissoko worked the ball right to Gerrard, whose cross was headed by Crouch past Maik Taylor, whose attempts to keep the ball out lacked conviction.
Crouch wasted two opportunities before collecting his 11th goal in 24 games. Luis Garcia was again allowed too much space as he weaved in from the right, eventually slipping the ball through to Crouch, who stroked his shot past the exposed Maik Taylor.
So numbed had Birmingham fans become that they briefly forgot to boo the former Aston Villa striker, although they raised a smile when the Tannoy announcer enquired: "Are you all going to the replay?"
Birmingham had moments of hope, mainly when Jermaine Pennant moved away from playing off Mikael Forssell and raced down the right flank.
But with Liverpool's foot on the accelerator, and Birmingham's on the self-destruct button, the goals continued to flow after the break. Fernando Morientes loped on for Crouch and promptly made it four. Steve Finnan drilled the ball down the inside-right channel, Luis Garcia dummied and there was Gerrard racing through before squaring the ball for Morientes to score with ease.
With 20 minutes remaining, Gerrard eased the ball into the path of John Arne Riise, who unleashed another of his trademark left-footed pile-drivers into the roof of the net. Police and stewards immediately formed a protective cordon in front of Bruce's dug-out, which tightened when Harry Kewell's cross-shot was turned in by Olivier Tebily and then Maik Taylor badly fumbled in a Djibril Cisse strike, a moment that encapsulated Birmingham's travails.