Around my house we have a rule about liquids in the bedroom. That rule is simply, "Don't." This was established after several instances of spills, stains, and residue from drinks. Even with this rule in place, there are still plenty of other ways for liquids to end up on our bed. That's why we bought a mattress encasement.
There's no good way to waterproof your entire bed. Your sheets and pillowcases will just have to fend for themselves. It's the non-washable items that really require attention. Your mattress obviously doesn't fit in a washing machine, and trying to remove liquids from the inside or clean them from the outside is a futile action. The best way to go about cleaning liquids from a mattress is to use a waterproof mattress encasement to avoid the issue in the first place. A waterproof mattress encasement will allow the liquid to bead up on top of the mattress instead of sinking inside. Think of it like a suit of armor for your mattress; it protects and prolongs the mattress's life.
In a similar vein, you will also want to keep your pillows liquid-free. While a pillow may fit in a washing machine, most pillows would be ruined by the process. Down pillows run the risk of being ruined just by the initial liquid spill itself. Luckily there are also pillow encasements available. These waterproof pillow encasements accomplish the same goal as the mattress encasements (keeping liquids away from expensive, hard to clean items).