Question: A doctor working in a hospital administers anaesthesia to a patient before an operation, and complications sometimes occur, rarely – at a rate of one or two percent. He only gives the patient a specified, standard dose. Is he liable for those complications?
The answer is that the doctor is not liable if he does not exceed what is customary. If he exceeds what is customary, he is liable.
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2