The purpose of this research study is to examine the effects of routine anesthesia on infant brain oxygen levels. The investigators do not know how anesthesia effects blood flow in the brain of infants during surgery. This study will help the investigators detect possible blood flow changes in the brain for infants undergoing anesthesia. A monitor and sensors (NIRS or near-infrared spectroscopy) which use light to measure oxygen levels in the blood will be used. Sensors will rest on the child's skin and record measurements before, during and after the surgery.

Pre-operatively medical history will be collected along with baseline physiological data (Blood pressure, heart rate, date of birth, date of surgery, weight, gestational age at birth, gender, medical conditions, and medications). Given the importance of reliable blood pressure measurement- during the study, strict guidelines regarding proper blood pressure cuff placement and choice of cuff size will be followed. An upper extremity and the cuff index lines will be used to make sure that the cuff is appropriately sized. NIRS sensors will be applied pre-operatively in the operating room prior to induction of anesthesia. All NIRS values will be collected as blind values so as to not influence anesthetic management or clinical decisions.

Intra-operatively the NIRS values will be blindly recorded, physiological data and details of the anesthesia (the conduct of all clinical monitoring, including blood pressure measurements and anesthesia will not be affected in any way by this study). No additional blood pressure or other measurements will be made.

One week later the hospital record (for those infants still hospitalized) will be reviewed for evidence of new changes in neurological status (specifically seizures or other generalized or focal neurological deficits noted by the clinical team in the record and physical exam). For infants discharged home prior to one week after surgery, a phone call will be made to inquire about the occurrence of any events that required medical attention or treatment.

Inclusion Criteria:

• Less than 6 months
• Scheduled for intubation/anesthesia for clinical purposes for a surgical procedure in the Children's Hospital of Philadelphia (CHOP) Main operating room that is expected to last longer than 30 minutes

Exclusion Criteria:

• Children where application of the NIRS would be impractical: for example surgery on the head or neck.
• Children scheduled for cardiac surgery
• Children with known major cardiovascular shunting
• Children with known or suspected neurological abnormalities

Children will be identified from the operating room schedules or, for emergency cases the coordinating anesthetist will contact the study team.