The first was a straightforward example of Da Vinci figuring out how to bring a nice cascade of stonework down on his attackers, thereby saving himself and his patron Lorenzo Medici, at least temporarily as far as Medici is concerned. He is badly hurt, which leads to the second Da Vinci feat, even more impressive than the first.
Da Vinci uses his accurate knowledge of the human circulatory system - better than the Roman Galen's - to work out a dangerous blood transfusion from him to Medici. The procedure is dangerous, that is, to Da Vinci, who is in good health, and not to Medici, who needs Leonardo's blood to live. It's unclear at the end of the episode if Lorenzo will survive - I hope so. History provides contradicting clues as to what might happen in the series. Lorenzo died of apparently natural causes in 1492 - not of wounds received from a knife in the neck - but we're likely in the year 1492 in the series, or close to it, with all the visions Leonardo is having about journeys to the New World. In fact, the opening sequence, which takes place some months in the future, shows Leonardo in the Western Hemisphere.
I'm find with this turn of events, which could be exciting, as long as it doesn't plunge the narrative further into the mystical, nonscientific track. The mysticism is already a fundamental part of the story, so it can't be completely abandoned, but the story works so much as better as historical science fiction, or even just historical fiction, than it does as fantasy.
See also Da Vinci's Demons: History, Science, and Science Fiction ... Da Vinci's Demons 1.7: Leonardo Under Water with a Twist ... Da Vinci's Demons Season 1 Finale: History, Science Fiction, Time Travel
Interested in a story with a passing reference to Leonardo? Try The Plot to Save Socrates ...