If you want to add some ambience throw in the strong smell, general filth and some buzzing flies. Accounts of Civil War hospitals abound with them.
The only thing I can tell you about pre-anaethesia battlefield amputations is that the majority of successful ones were the ones done most quickly, as the patient was likely to die from just the shock of the pain alone, so working fast was the major premium for doctors here.
Also, wasn't the wound usually cauterized rather than stitched? And how does the arm fall on the floor when it's tied to a heavy block?
However, these are just details, the main point is that it's well-written and, like Rc said, emotionally unified. These are the important things. (If someone is really knowledgeable about the finer points of pre-anaethesia amputations you may not WANT them for readers, just kidding.