Objective To investigate the application value of transcranial Doppler ultrasonography(TCD) in critically ill children with cerebral dysfunction.Methods We detected the cerebral blood flow parameters[systolic velocity(Vs),mean velocity(Vm),end of diastolic velocity(Vd),pulsatility index(PI),resistance index(RI)] of middle cerebral artery in cerebral dysfunction group(n=20) and control group(no cerebral dysfunction,n=20),and observed the differences of those parameters between two groups.Children in cerebral dysfunction group were also divided into groups according to Glasgow Coma Score(GCS) and prognosis.The differences of each TCD parameter in diverse groups divided by GCS and by prognosis were analysed.Children in cerebral dysfunction group were checked TCD everyday until TCD parameters were normal.The relation between the days of TCD parameters′ reaching normal and GCS,duration of disorder of consciousness with correlation analysis were analysed.Results Vs,PI,RI in cerebral dysfunction group were higher than those in control group,while Vd was lower (P<0.05).(2)PI in the group of GCS less than 6 points(0.91±0.21) was higher than that in group of GCS 7-13 points(0.83±0.14)(P<0.05).The other parameters between two groups of GCS less than 6 points and GCS 7-13 points were not significantly indistinctive.Between the good prognosis group and the bad prognosis group,there were no significant differences in all parameters.(3) The days of TCD parameters′ reaching normal were negatively correlated with GCS(r=-0.653,P<0.01),but positively correlated with the duration of disorder of consciousness(r=0.923,P<0.01).Conclusion The cerebral hemodynamics of children with cerebral dysfunction is abnormal,the more serious cerebral dysfunction,the higher PI and the longer time for regaining normal TCD parameters.Constantly monitoring TCD could reflect the changes of cerebral hemodynamics and is valuable to assess the state of illness and prognosis.