For example, anaesthetics were significant in the 19th century as it meant that patients no longer suffered pain and died of shock. This enabled surgeons to begin to develop more complicated procedures.
The problems for patients were pain, infection and bleeding. The development of anaesthetics such as chloroform, which was discovered by James Simpson in 1847, greatly improved the success rate of surgery. Anaesthetics weren't always popular though as they were uncomfortable for patients.