Caudal epidural block has been widely used, especially in pediatric surgery, to supply intraoperative and postoperative analgesia by affecting the region between T10 and S5 dermatomes in surgeries below the umbilical level.

In conventional single-shot caudal block, the needle is inserted through the skin with a 60-80 degrees angle, until the sacrococcygeal ligament is passed through. Then the angle of the needle is decreased to 20-30 degrees and inserted further for an additional 2-3 mm, entering into the sacral canal.There is a risk of dural or vascular puncture when the needle is passing through sacral canal. Other complications are the soft tissue bulging, intraosseous injections and systemic toxicity.

Many anatomical variations have been reported for sacral hiatus and sacral cornua. Therefore, the success rate of the classic caudal epidural anesthesia method in pediatric patients has been reported to be about 75%.

With the usage of ultrasonography in regional anesthesia, many advantages have been reported. In particular ultrasonography under longitudinal image is helpful for visualization of the sacral hiatus, sacrococcygeal ligament, duramater, epidural space and the distribution of the local anesthetic agent Therefore, this significantly increases the block success and visualization of where local anesthetic is injected.

The primary aim of this study was compare the success rate of ultrasound guided sacral hiatus injection and conventional sacral canal injection. Secondary objectives are; block performing time, number of needle puncture, success at first puncture and complication rate. However age and weight encountered wtih these complications are registered.

The caudal block was performed in Group C by via conventional methods. The sacral cornus and the sacral hiatus were palpated. After sterilization of the region, a 22- gauge caudal needle was inserted into the skin with at a 60-80 degree angle and until the sacrococcygeal ligament was passed punctured, as determined with by a "popping sensation." feeling (puncture of the sacrococcygeal ligament). Then, the angle of the needle was then reduced to 20-30 degrees and inserted further for an additional 2-3mm, entering into the sacral canal. After verifingverifying the absence of any blood or cerebrospinal fluid in the aspiration, a test dose of 0.1 ml/kg of local anesthetic (LA) with adrenalin at a ratio of 1: 200000 was injected under hemodynamic and ECG monitoring. Following a negative test dose, the rest of the LA was slowly injected slowly over 1 min. In the case of the needle touching the bony tissue, blood aspiration, or bulging into of the subcutaneous tissue, the angle of the needle was changed and the intervention was repeated.

The caudal block was performed by via ultrasound guided ultrasound guidance in Group U. After sterilization of the region and using ultrasound guidanceUSG with a sterile plastic cover and gel, the sacral hiatus was visualized via an out-of-plane technique at the level of the sacral cornus at the out of plane via the lineerlinear transducer of an M-Turbo ultrasound machine (TM; Fujifilm SonoSite Inc., (Washington, WA, United StatesUSA) ultrasound machine at 13 MHz, and the, depth and gain was adjusted to for optimal visual quality. The ultrasound ultrasound transducer was first placed transversely at the midlain midline to obtain the transvers view of the two cornua, the sacrococcygeal ligament, the sacral bone, and the sacral hiatus. At this level, the ultrasound ultrasound transducer was rotated 90 degrees to obtain the longitudinal view of the sacrococcygeal ligamantligament and sacral hiatus, and was then placed between the two cornua. A 22- gauge caudal needle was advanced toward the upper third of the sacrococcygeal ligament. The needle advancement was terminated right after penetrating the sacrococcygeal ligament. At this level, after confirming the absence of any blood or cerebrospinal fluid in the aspiration and a negative test dose, the rest of the LA was injected over 1 min under while observing the ultrasound ultrasound longitudinal image

Inclusion Criteria:

• ASA (American Society of Anesthesiologist) I children aged between 6 months and 8 years old who underwent elective hypospadias, circumcision and both surgery

Exclusion Criteria:

• Severe systemic disease, previous neurological or spinal disorder, coagulation anomaly, allergy against local anesthetics, local infection at block site or with a history of premature birth

Double Participant, Outcomes Assessor