The ideal method to predict successful caudal block is still lacking. We hypothesized that the change in femoral artery Doppler indices could accurately predict successful caudal block

after institutional research ethics committee approval and obtaining informed consent from each participant. an experienced operator will examine the femoral artery using pulsed wave Doppler at baseline and 15 and 30 minutes after caudal block adminestration

Inclusion Criteria:

• ASA1 or 2 lower abdominal or lower limb surgery

Exclusion Criteria:

• allergy to bupivacaine parental refusal coagulopathy inability to obtain adequate femoral artery views

Pediatric patients undergoing abdominal or lower limb surgery under general anesthesia combined with caudal block

Data regarding this study will be available from the corresponding author upon reasonable request