The proposed studies are aimed to measure Tau and P-Tau levels in pre- and postoperative blood, urine, feces and saliva, as well as to assess pre- and postoperative neurocognitive function in children (3 to 5 years old) who will have surgery under general anesthesia (single versus multiple exposures). The studies will establish a system to study biomarkers of the anesthesia/surgery-associated neurocognitive impairment in children and generate hypothesis that Tau or P-Tau serves as the biomarker of such neurocognitive impairment in children.

This proposed studies have two specific aims:

1. To investigate the relationship between pre-operative or postoperative blood levels of Tau or P-Tau and neurocognitive outcomes. The working hypothesis is that pre- and postoperative blood Tau/P-Tau levels are higher in participants who develop neurocognitive impairment than those in the participants who do not develop it. The investigators will perform neurocognitive test before the surgery and then at 12 months after the surgery. The investigators will collect pre-operative and postoperative blood and measure Tau/P-Tau levels in the blood. Finally, the association of the changes in the Tau/P-Tau levels and neurocognitive scores will be assessed. More importantly, this Aim will establish an eligible: recruit ratio, retention rates, safety of the protocol, and power calculation, which will provide crucial information to guide better design of future R01 study.
2. To perform the feasibility studies of measuring Tau or P-Tau in urine, feces and saliva of the participants. The working hypothesis is that Tau/P-Tau in urine, feces or saliva of children can be measured. The investigators will use the nanobeam to measure Tau/P-Tau levels before and after the surgery. The investigators will then determine whether urine, feces and saliva can be used for the future studies to develop Tau/P-Tau as the biomarker of anesthesia/surgery-associated neurocognitive impairment in children.

Inclusion Criteria:

1. between age 3 and 5 at the time of the first neurocognitive test;
2. scheduled for surgery under general anesthesia

Exclusion Criteria:

1. gestational age less than 36 weeks;
2. congenital heart disease that has required surgery or will require surgery or that requires ongoing pharmacotherapy;
3. known chromosomal abnormality or any other known acquired or congenital abnormalities which are likely to affect neurodevelopment;
4. known neurological injury such as cystic periventricular leukomalacia or grade 3 or 4 intra-ventricular hemorrhage (+/- post hemorrhage ventricular dilatation);
5. children for whom follow-up would be difficult for geographic or psychosocial reasons;
6. non-native English speaker (both child and parents);
7. severe visual or auditory disorder.

The investigators will enroll participants between age 3 and 5 years old who are scheduled for the surgery under general anesthesia from Shriners Hospital for Children or Boston Children Hospital.

All individual participant data that underlie results in a publication will be available to other researchers.

Individual participant data will be available 6 months after publication

Principle investigator will review the requests and determine what information should be shared.