Iced tea
When they were operating in Fabi the drip bottle looked like it had iced tea in it.
shareIt was probably albumin or blood plasma. Both are amber-ish in color.
Albumin - http://www.baxter.com.pr/images/healthcare_professionals/products/buminate.jpg
Blood plasma - http://www.visualphotos.com/photo/1x6072296/transfusion-bag-containing-blood-plasma.jpg
In 1949 those two are much more commonly used as volume expanders in a bleeding patient than whole blood, which has a short shelf life.
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Also interesting nobody has mentioned the cause of Fab's hemmorhaging: a self-induced abortion? Quite the shocker for a 1949 film.