Elbows have a high chance of opening cuts on the face, which tend to bleed profusely no matter how bad they actually are. This was actually one of the growing number of fights that they stopped due to them, however.
Typically it's cuts near the eye that cause the doctors to take a look, and since Carlos had basically obtained a fetish for them for the second half of that entire round after he landed a massive pair of them, Thiago Alves's face was basically mincemeat at that point. Crazy stuff.
But like I said, some people look at it differently. Some see the heart on Thiago's part to keep fighting through it even as he was leaking profusely and have a deep admiration and respect for that breed of determination.
Others saw the adjustment on Carlos's part from his notoriously unreliable punching technique that was leaving him stumped at the end of Thiago's boxing for one and a half rounds, to the shorter, harder, and considerably more forceful elbows that changed the tide in his favor, and his ruthless exploitation of the technique as soon as he recognized how well it was working.
Others still just love it for the "HOLY SHIT" factor of two guys swinging at eachother like absolute madmen, and one using a solid chunk of bone to lacerate someone's face and literally flatten his nose. Jesus fucking Christ.
And the craziest part of it all is that Lawler vs. MacDonald II at 189 was an even bloodier back-and-forth war. Imagine that, but with both people beating eachother up for the better part of 25 minutes.
It's a crazy fucking sport, and the fact that it's all real makes it even crazier. No storylines, no scripts, nothing to obfuscate the outcome. Just one man's skill, athleticism, training, and strategy against another's.