I believe this to be an unfair and way too broad of a question to answer in just one block of information. Practitioners are held responsible for medical treatments, not identifying potentially deadly consequences of an injury or giving a medication, but most people that work in an institution work with a collaborating team. It usually is not one person who is doing all the work unless you are speaking of a mishap in surgery or a medication that was ordered by a provider and given by a nurse which caused a terminal problem/issues/consequence for the patient. In the legal arena we are taught as providers to assess, evaluate, treat, and make differential diagnosis based on our personal knowledge and most often by collaborating with other providers. Yes, legally it is our responsibility but it can not be answered in such a manner that the question is being asked. A specific case, situation, area of medicine, etc needs to be addressed to further answer this question.
No, of course not. Satisfactory medical outcomes are not guaranteed, even with the best medical treatment. Medicine is a science, but it is not an exact science. There are far too many variables inherent in any medical treatment or procedure. Being legally liable for an unsatisfactory medical outcome would require that a health care practitioner had been reckless or negligent in some way in treating a patient and that his or her actions had caused harm. When a health care provider is sued and the case goes to court, the jury decides if the provider should be held liable and if damages should be awarded to the patient who has sued.
A health care professional has the legal responsibility, while treating his patients, to follow the the right procedures, and prescribe medicines and other treatments in line with the accepted professional knowledge. Similarly, in performing operations or carrying out other similar procedures the physician must possess and use adequate skills. Also, he must take other necessary precautions such as availability of adequate facilities and material for the operation and maintenance of standard of hygiene.
The actual outcome of medical treatment may be not be satisfactory, in spite of all such necessary precautions being taken. This is because medical science is not a perfect science. Most of the medical treatment and medicines are are such that these help majority of the patients in majority of the cases, but they do not guarantee 100 percent satisfactory results in all cases. Therefore the medical practitioner has no legal responsibility for unsatisfactory medical outcome in spite of satisfactory treatment.