In addition to the above, I'd add that it's a very good idea to pace yourself. Find a sustainable rate to review items, rather than trying to rush through it.
I've always tried to clear out my review items every day in order to prevent backlog, but things come up. After the recent server issues, for example, I found myself with almost a thousand items due for review.
Rather than trying to burn through them all as fast as I can though, I'm doing it bit by bit. I review a hundred items around the start of my day, do something else for a few minutes, then review another hundred. I then repeat the process later in the day, bringing the total to around 400 items per day. The idea is to review more than is coming in every day. In my case, I average something around 200 items coming up per day, so as long as I keep at this rate, I'll eventually catch up.
Another good reason not to burn through the entire backlog all at once is that all of those items will then stay 'clumped together', meaning that later on, once the next review cycle comes around, you're going to get a huge batch dumped on you all at once, which is never fun.
So I'd suggest setting up something of a priority list with your courses (I use the 'Groups' screen for this), so you can slowly work your way through that. As long as you continue to do more than what's coming in, you'll eventually get there.