This study is a prospective study of epidural pressure changes when local anesthetic is injected from the caudal route. All patients will receive the same weight based volume dose of local anesthetic after induction of general anesthesia, and a CVP transducer will be attached to the standard caudal needle for measurement of pressure: under the skin, after entering the epidural space, and every 15 seconds for 3 minutes after completion of injection with the needle in situ. The placement of the caudal epidural will follow current standard of care and administration, the only variation will be the addition of a pressure transducer to the stopcock where the local anesthetic syringe is attached that will allow for pressure monitoring.

After approval of the Internal Review Board, the patients and families will be given the opportunity to participate in the proposed research study if inclusion criteria are met. The patient/family will sign the anesthesia consent form, as per protocol, by initialing the box at the bottom that states 'I do want, if indicated, regional anesthetic techniques employed for anesthetic maintenance and/or port operative pain relief for my child.' The primary anesthesia team (anesthesiologist/CNRA/resident) will be made aware that the need for a pressure transducer for the caudal epidural injection will be required and that a member of the research team will be documenting pressures during the procedure. Premedication with midazolam will be at the discretion of the attending anesthesiologist covering the case. Anesthesia induction may be performed with either intravenous medications or mask inhalation at the attending anesthesiologist's discretion; however no narcotics will be administered during induction, as is common when a caudal epidural is utilized for post-operative pain control. The airway will be secured using an oral endotracheal tube or laryngeal mask airway (LMA).

The single shot caudal epidural block with pressure monitoring will be performed by one of the study investigators. Ropivicaine/Bupivacaine 0.125-0.25% will be used as the local anesthetic for the caudal epidural with a total dose not to exceed 1 ml/kg. Pressure transduction will be constantly in place, with pressures being recorded by a research nurse: 1) prior to entering the epidural space, but after needle introduction under the skin, 2) after loss of resistance upon entering the epidural space, 3) at 5 second intervals during injection of the 1 mL/kg bolus of local anesthetic 4) continuing with pressure monitoring for an additional minute, in 10 second increments, after the injection is completed. Following placement of the block, a band-aidwill be placed, where appropriate, and the patient will be prepped for the surgical procedure. The primary anesthesia team will continue delivering the general anesthetic for the remainder of the case. Maintenance anesthesia will be carried out per our usual routine.

Upon completion of the surgical procedure, the patient's airway device will be removed and the patient will be transferred to the post-anesthesia care unit (PACU). In the PACU, the principal or co-investigator will review the patient's treatment needs for pain in the PACU to determine whether the block was efficacious; fentanyl 0.5 µg/kg, or the morphine-equivalent dose, will be administered as necessary based on the pain assessment. The patients will be discharged from PACU when discharge criteria are met per the Aldrete score.

Inclusion Criteria:

1. ASA physical status I or II
2. Weight ≥ 3 kilograms
3. Undergoing a lower abdominal/pelvic or urologic procedure where caudal epidural anesthesia is a beneficial adjunct

Exclusion Criteria:

1. Co-morbid diseases (cardiac, pulmonary, neurological disease)
2. Patients with sacral deformities contraindicating a caudal epidural
3. Use of therapeutic dose anticoagulants or presence of a bleeding disorder
4. Other co-existing conditions would preclude the use of neuraxial blockade

Patients who will be receiving caudal anesthesia as part of their surgical procedure.