Due to
administration of anaestheia (be it general anaesthesia in which patient is
completely unconscious or regional in which the patient is awake and only a
part to be operated is anaesthetized) the patient is asked prior to operation
or after the operation not to consume any fluid or food, so as to avoid a
deadly complication of any risk of aspiration into the lungs.
Due to fasting the patient has
empty stomach, so the risk of aspiration is reduced. During operation patient
is also administered sedatives and
anxiolytics, which may have a residual effect for some time after operation,
which alters the active airway reflexes of patient. Nausea vomiting is a common
manifestation after operation as a side effect drugs and inhalation agents used
for sedation. So initially patient is started with only light food and fluids
post operation after prescribed hours for both. Thus the main reasons are to
avoid vomiting, and ensure rest to bowels.
