a) Regional anesthesia in neonates is an acceptable option when the risks of complications during or after general anesthesia and endotracheal intubation are very high for anatomic or physiologic reasons.

b) These techniques have allowed surgical procedures to be done on critically ill neonates under minimal general anesthesia, with considerable reduction in the need for CNS depressant drugs.

c) An additional benefit to the use of regional anesthesia in this age group is postoperative pain control. The two most common techniques used in neonates are the spinal and caudal epidural blocks.

d) Anatomic differences in the neonate should be considered, particularly the location of the terminal end of the spinal cord, the dural sac, and the volume of cerebrospinal fluid (CSF).

e) The spinal cord extends as far as L3 in newborns and neonates and does not reach the adult position of L1 until 1 year of age. The dural sac extends to S3 to S4 in these babies and does not reach the adult position of S1 until approximately 1 year of age.

f) The volume of CSF is twice that of adults (4 mL/kg vs. 2mL /kg, respectively). This dilutes the local anesthetics injected and could explain the higher dose requirements and shorter duration of analgesia.

g) Bradycardia and hypotension are not often seen. It is thought that this could be because of the immature sympathetic nervous system or the proportionately small blood volume in the lower limbs, decreasing the amount of venous pooling.

h) The ventilatory response to the regional anesthetic is related to the level of the block. With a level as high as T2 to T4, there could be intercostal muscle weakness that requires the dependence on diaphragmatic movement for tidal breathing; however, tidal volume and respiratory rate are not usually affected.

i) There are pharmacologic considerations when regional anesthesia is used in neonates. The extracellular space is larger. This means the initial dose of local anesthetic is diluted into a larger volume of distribution, resulting in a lower initial plasma peak concentration.