hi, can be done under regional anaesthesia or local anaesthesia.biggest disadvantage patient goes for hyperventilation to combat hypercarbia leading to excessive movements in the sugical field hampering surgery.2nd disadvantage hypoxemia due to trendelenberg position & reducedFRC.at the same time reduced cardiac output due to sympathetic blockade caused by regional anaesthesia.should go for regional or local anaesthesia only if patient not fit for GA.WITH REGARDS.