Pediatric Caudal Injection Volume on Optic Nerve Sheath Diameter and Cerebral Oxygenation

The Effect of Caudal Epidural Injection Volume on Optic Nerve Sheath Diameter and Cerebral Oxygenation in Pediatric Cases

Caudal anesthesia is a commonly used neuraxial anesthesia method for children. Injection of a certain volume of fluid into the epidural space for cauda anesthesia may push some cerebrospinal fluid towards the head, which may lead to mild increase of pressures inside the head. Such mild changes are compensated well by healthy individuals and no clinical sequel is seen, however at-risk populations may be affected. We aim to see how different amounts of fluid injected into the epidural space may change two clinical parameters affected by intracranial pressure to determine if a lower volume is safer than a higher one.

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.

Investigator, who will take and record the measurements, will not know about the volume of caudal injection. Another investigator will analyze the ultrasonography images without any knowledge of the patient or the intervention.

Difference in the percentage change of ultrasonographic measurement of optic nerve sheath diameter between groups

Difference in the change in near-infrared spectrometry measurement of cerebral oxygenation between the groups

Difference in the percentage change of ultrasonographic measurement of optic nerve sheath diameter in each group

Difference in the change in near-infrared spectrometry measurement of cerebral oxygenation in each group

Mean arterial pressure, heart rate, end-tidal carbondioxide pressure, peak inspiratory pressure, peripheral oxygen saturation, oxygen fraction of inhaled gas

Inclusion Criteria: ASA class 1 or 2 Scheduled for elective surgery suitable for caudal anesthesia Parental/guardian consent for caudal anesthesia and measurements obtained Closed fontanelles Exclusion Criteria: Open fontanelle Parental/guardian refusal Previous intracranial or ocular pathology Coagulapathies Variations in gross and ultrasonographic sacral anatomy Block performence to end of surgery expected to last less than 30 minutes Block volumes more than 30ml needed Laparoscopic surgery Need for long term analgesia with epidural catheter