Objective       To evaluate the safety and effectiveness of an improved caudal blocking under ultrasound guidance for infants undergoing  herniorrhaphy.       Methods       Sixty infants of American society of anesthesiologists (ASA)ⅠorⅡ

aged from 4 to 12 months

undergoing selective herniorrhaphy in our hospital were prospectively enrolled in this study. They were randomly divided into 2 groups (n=30)

and respectively received conventional or improvement anesthetic methods. In both group

1 mL/kg 0.15%  ropivacaine  at a rate of approximately 0.5 mL/s was given for caudal blocks

while ultrasonography was used to observe local anesthetic in the epidural space of the improvement group. Gender

age

weight

and ASA physical status were recorded. Vital signs such as electrocardiographic parameters

non-invasive blood pressure

respiratory rate and pulse oximetric indexes were recorded at the time of after anesthesia induction (t1)

beginning of the operation (t2)

10 min after the beginning of the operation (t3)

and the end of operation (t4). Total time required to insert needle into the caudal space

number of attempts required for successful block

number of bloody taps and dural puncture were recorded. Other data included results of the highest portion which the local anesthetic reached.       Results      All of the blocks were judged to be clinically successful. The conventional method group had 86.7% reaching the highest portion of local anesthesia L1

while the improvement method group had 83.3%. The mean time required to perform caudal block and the failure rates at the first attempt of caudal block was 299.9±35.6 s and 16.7% in the conventional method group

and 297.6±28.4 s and 3.3% improvement method group. There were 3 cases of bloody tap and 1 of dural puncture in the conventional method group

but no such case was found in the latter group.       Conclusion        Improved caudal block anesthesia under ultrasound guidance increases the chance of a successful caudal injection

attenuates the incidences of complications

and obtains good caudal blocking at the same time.