Objective       To determine the brain protective effects of isoflurane pretreatment in infants undergoing open-heart operation with cardiopulmonary bypass (CPB).       Methods       A total 42 infants (less than 3 years old) with congenital heart diseases who received surgical treatment in Yongchuan Hospital and Children’s Hospital during December 2008 to December 2010 were prospectively and randomly divided into 2 matched groups

isoflurane pretreatment group (n=21) and control group (n=21). In isoflurane pretreatment group

all infants had been inhaled 1 to 1.5 MAC isoflurane continually for over 60 min after ventilation followed  by conventional anesthesia

while control group received conventional anesthesia without pretreatment. Blood samples were taken before (T1) and in 5 min after CPB (T2)

immediately after aortic crossclamping (T3)

in 30 min after CPB (T4)

end of CPB (T4)

and in 6 and 24 h after the end of CPB (T6 and T7). Serum levels of S100β protein and neuron-specific enolase (NSE) were measured by ELISA.       Results      There was no significant difference in the serum levels of S100β protein and NSE between the 2 groups before operation. But

for the pretreatment group

their serum levels rose slowly but with no significant difference among all the time points before and after CPB (P0.05). In contrast

in the control group

there was significant differences in the serum levels at T3

T4 and T5 compared with at T1 (P0.05)

though no difference was found when compared with T7(P0.05). Their serum levels of S100β protein and NSE reached the peak at T5 and T7. The levels of f S100 and NSE in control group at T4 to T6 were significant higher than those in pretreatment group (P0.05). The level of S100β was positively correlated with that of NSE in both groups (r=0.684 and 0.648).        Conclusion      Isoflurane pretreatment significantly decreases the serum levels of S100β and NSE during open-heart operation in infants with cardiopulmonary bypass.