A ‘General Anaesthetic’ involves administering medications to temporarily send you to sleep. This is often necessary for surgery. Modern general anaesthesia is very safe, although there are a number of early side-effects which occur straight after surgery and do not last long. These can include feeling sick, vomiting, dizziness or a sore throat.
Rarely there is the possibility of severe complications such as an allergic reaction to drugs, waking up during surgery (awareness) or even death (which occurs in approximately one of each 100,000 cases)
For more information about what to expect from an anaesthetic as well as an explanation of the risks please visit:
https://www.nhs.uk/conditions/general-anaesthesia/
Some surgery can be carried out under local anaesthetic. This involves an injection to numb the area before the operation starts.  Generally the risks are lower from a procedure under local anaesthesia, but there are still risks including discomfort during injection, tingling and minor bruising
For more information about what to expect from a local anaesthetic as well as an explanation of the risks please visit:
https://www.nhs.uk/conditions/local-anaesthesia/