A caudal epidural block is among the most widely administered techniques of regional anesthesia in pediatric patients. It helps in reducing the intraoperative dose of inhalational anesthetic agent used for maintenance of anesthesia and in addition provides an excellent postoperative analgesia without the side effects of intravenous opioid medication, like nausea and vomiting during emergence, cardiovascular, and respiratory depression. the aim of the study was to assess, perfusion index (PI) as an indicator for success of caudal block onset in pediatric patients scheduled for elective surgery of lower abdomen, pelvic region, genital region, or lower limbs.

with guidance of ultrasonography.

It is performed by inserting a needle through the sacral hiatus to gain entrance into the sacral epidural space. Using conventional blind technique, the failure rate of caudal epidural block is high even in experienced hands. With the advent of ultrasound in guiding needle placement, the success rate of caudal epidural block has been markedly improved and could be effective in preventing complications during caudal epidural injection. After administration of a caudal block, reliable assessment of caudal block is very crucial to ascertain the success of block. The onset of caudal block is often assessed by cold stimuli and cutaneous temperature changes. Caudal block in pediatric patients is often performed under general anesthesia. Hence, testing the sensory levels by above techniques cannot be used. Also the change in the hemodynamic parameters are few other assessment methods. These methods are to be used 15-20 min after block administration, to confirm the efficacy of a caudal block. Perfusion index (PI), independent of parameters like heart rate, oxygen saturation of blood, or body temperature, measures the ratio of arterial blood flow (pulsatile flow) to venous, capillary, and tissue blood flow (non-pulsatile blood flow) and it is shown in percentage or absolute value . PI is considered as a sensitive marker to assess the efficacy of caudal block. It can detect the onset of caudal block, by increasing PI beyond the pre-induction values, which can be due to the sympathectomy induced after successful caudal administration,which increases the blood flow to the peripheral tissues.

Inclusion Criteria:

• -ASA physical status I-II. -Both sexes -Age between 2 and 10 years -Patients scheduled for elective surgery of lower abdomen, pelvic region, genital region, or lower limbs.

Exclusion Criteria:

• ASA physical status more than II.
• Patients having any neurological disorders, bleeding disorder, bony deformity of vertebral column.

infection at the injection site, drug allergy, and undergoing anal surgery.