i got to room 49 with 3 hearts. this is how i did it-
first, load up on potions, arrows, bombs, etc. before the cave. make sure you have at least 90 bombs, 100 arrows, 4 bottles with blue potion or a fairy, and in your case, i advise 15 hearts.
the trick is to beat most of your enemies while you're on the ledge. not all enemies can be beat like this, but you can get rid of keese (bats) with the clawshot or the boomerang for example. if you plunge in blindly, you'll be surrounded and may lose hearts.
also, you should form a plan before jumping off the ledge. don't rush in without one.
strong enemies such as that red mummy dude and the armored lizard (i'll learn their names later!) will be a pain to take out with your sword. for these two, i recommend bomb arrows!
don't run around as wolf link too much. wolf link takes a lot more damage, and his midna charged attack leaves him vulnerable.
if enemies start shooting arrows at you when you're on the ledge, block with the hylian shield, and draw your bow. hold z to move around while aiming, and shoot the enemies quickly.
if surrounded by minor, annoying enemies such as the rat dudes, try using the spinner or a well-placed bomb.
if there are several medium-level enemies at the center, use the jump strike to dispatch of most of them.
i have quite a few more tips, but this should help you out. if you need more advice, just ask.