The Comparison of Laryngeal Mask Airway and Endotracheal Tube in General Anesthesia for Premature Neonates

Inclusion Criteria: * preterm neonates (gestational age \< 37 weeks) in our neonatal ward scheduled to receive unilateral or bilateral inguinal hernia repair surgery, and whose body weight \> 2000g at surgery Exclusion Criteria: * emergent surgery, infants who was intubated before surgery, long-term oxygen or mechanical ventilation dependence, severe congenital cardiopulmonary disease, lacking of birth history, combination with other major surgery, postmenstrual age \> 52 weeks at surgery