Yes. The Brazilian Butt Lift is still an option even if you have previously had Hydrogel injections in the past. Having had Hydrogel previously should not change your results. The main issue is to be sure the procedure is done well by a surgeon who is experienced with this procedure.
Also, hopefully you really have Hydrogel. Unfortunately, I have seen patients who have been told that they were being injected with Hydrogel, but found out later that they had been injected with Silicone. Hydrogel is very expensive and many of the unscrupulous people who perform these 'butt injections" substitute the much cheaper silicone for use in place of the very expensive hydrogel. If this is the case, it might change things a little.
Web reference: http://www.DiscoverTheBeauty.com