A fever before surgery is an added risk and your child's surgery will be cancelled. If your child develop a slight fever after an anesthetic, this is normal. The fever should go away within 24 hours of the anesthetic. Give your child plenty of fluids and the medication your child’s doctor recommends for a fever.
If it doesn't go away within 24 hours, take your child to their family doctor. If the fever is very high (above 38.5 degrees Celsius/ 101.3 degrees Fahrenheit), take your child to the emergency department.
Learn more about fevers at AboutKidsHealth.ca: