In the Wild West or Civil War, or just before the 1880's if someone got shot in the stomach, they were goners. Not amount of medical attention could save you.
Today, a gunshot wound to the stomach is a very survivable injury thanks to modern medical technology.
Today, if you fell into a lava flow, you're a goner. We can't heal all the burns and build respirator suits. (By the way, did the lava get into his lungs or something? HEY! Shadows of the Empire said his lungs were destroyed! Oh well, that obviously didn't happen)
In the future, you can obviously survive falling into lava. Also, thanks to General Grievous, you can apparently survive as only eyeballs, a brain, and a heart. You don't have to have lungs, but you can still wheeze. Especially after seeing Grievous, Obi-Wan should have known that Anakin's injuries were survivable and brought him to his ship for a quick trip to Padme's hospital.
Now, from my personal experience as a kids, even if i was fighting with my mother friehours before, if i got injured and needed to go to the Emergency Room, she quickly became my favorite person b/c she was taking care of me.
When you're scared and in pain, you don't appreciate anybody more than your doctor and whomever is taking care of you....if Obi-Wan nursed Anakin back to health Anakin would be totally indebted to him. Plus, seeing his kids would have given him a reason to heal. If he knew the Empire wanted them, he's be filled with a desire to protect them. Padme wouldn't have died.
Its so stupid!