Caudal epidural injection of local anesthetic solution is a common neuraxial anesthesia technique that provides excellent peri-operative analgesia in children. Unfused sacral hiatus allows for easy and safe access into the epidural space. Anatomically, injection of a certain volume of fluid over the dural sac inside the closed spinal canal can push the cerebrospinal fluid cranially. This push may lead to increased intracranial pressure. We will measure two findings affected by intracranial pressure (optic nerve sheath diameter and cerebral oxygenation) and compare the effects of two different volumes of caudal injections on these measures.

Children with closed fontanelles and scheduled to undergo elective surgery, for which caudal anesthesia is an effective method for peri-operative analgesia, will be recruited for this study. Injection volume will be determined depending on the level of analgesia required for the surgical procedure. Ultrasonographic measurements of optic nerve sheath diameter and near-infrared spectrometry measurement of cerebral oxygenation will be taken before and after caudal anesthesia.