Alm888: Well, the rat is a sub-boss, for all intents and purposes. It is entirely avoidable and is not gonna go anywhere so you can fight it anytime you want (it is a good idea to get some levels and a decent weapon first).
And, regarding your situation… Why can't you leave the area? Try to run towards the ladder and then "use" the ladder (warning: using/checking stuff midfight requires 4 AP, AFAIK, so you may not be able to use the ladder the axact turn you have reached it. Try to survive till the new turn while standing next to it).
gcman: No, once combat is initiated you cannot leave. I tried it again with full AP's. I really hate to skip it for later as I always like to finish every area before going on and later it may not be worth coming back to . I need the money now.. Thanks for your response.
What's your char build? I just stabbed him to death with a shiv (which luckily didn't break during the battle). I did almost die though.
Note if you have 4 AP and some food in your inventory, you can just go to inventory and heal. You can use as many food/healing items as you need once you've opened the inventory up. Do that once you're almost dead, then continue - should be easily doable if you have some meat, canned meat, fish etc.
I wouldn't use medic items this early BTW - they're kind of expensive (so lucky you ended up with two this early!), and best given to companions (since they can use them during combat automatically).