Wash yeast from an 11.5% beer?

I am about to bottle an 11.5% beer that fermented down to 1.000 with WLP545. I would like to brew up a Belgium Blonde with an OG around 1.056. Do you think I could use this yeast, or has it been stressed to the limit?

Yes you can reuse it but you will probably find you really need to baby the starter to get the yeast moving. The more important question is whether you want the yeast you have for future beers. The yeast that survived are the strongest but not necessarily the ones that produce the best flavor. I would test out a small batch of a straightforward blonde ale to see if there's off flavors before committing a whole five gallons to the yeast. Or you could just buy new yeast.

Don't use this yeast, it's donzo. General rule of thumb for washing yeast is you want to go lower to higher in terms of OG, color, and bitterness.