In each session, I always try to gradually crank up the tension and danger, so that the final combat encounter (assuming that it is a combat encounter) is the most difficult (read deadly). However, this means that a few PCs do get knocked unconscious, sometimes fairly early in the combat (although that will usually be due to their own bad decisions).
The players of these characters then have the unenviable prospect of sitting through most of the rest of the combat, rolling death saving throws, while everyone else has fun. The party does not have access to much in the way of healing, so once unconscious, the characters tend to stay that way. Even worse, if they get stabilised, they have even less to do, as they don't even have to roll death saving throws any more.
How can I keep these players entertained, while still ensuring that the party is in danger? (e.g. I want characters to fall unconscious if their plan fails).