Chapter 42. Pediatric Epidural and Spinal Anesthesia and Analgesia
Anatomical differences in children compared with adults that should be considered when using neuraxial anesthesia are:
A. The conus medullaris is located higher in the spinal column.
B. The sacral hiatus is located more cephalad than in older children.
C. Below 1 year of age, the dural sac is more cephalad.
D. The epidural fat is densely packed in small children.
B is correct. In young children, the sacral hiatus is located more cephalad than in older children. The sacrum of children is also more flat and narrow compared with the adult population. At birth, the sacral plate, which is formed by five sacral vertebrae, is not completely ossified and continues to fuse until approximately 8 years of age (although it may take until 21 years of age). There is a 6% incidence of sacral atresia. The incomplete fusion of the sacral vertebral arch forms the sacral hiatus. The caudal epidural space can be accessed easily in infants and children through the sacral hiatus. Because of the continuous development of the sacral canal roof, there is considerable variation in the sacral hiatus.
A is incorrect. There are significant anatomical differences in children compared with adults that should be considered when using neuraxial anesthesia. For instance, in neonates and infants, the conus medullaris is located lower in the spinal column (at approximately the L3 vertebra) compared with that in adults, in whom it is situated at approximately the L1 vertebra. This is a result of different rates of growth between the spinal cord and the bony vertebral column in infants. However, at approximately 1 year of age, the conus medullaris reaches the L1 level similar to that in an adult.
C is incorrect. The dural sac may end more caudally: at S4 in infants younger than 1 year and at S2 in older children. Therefore, because of the increased risk of accidental dural puncture, caution is warranted when placing caudal blocks in infants.
D is incorrect. The loosely packed epidural fat may facilitate the spread of local anesthetic and help achieve a quicker block onset. It may also allow the unimpeded advancement of epidural catheters from the caudal epidural space to the lumbar and thoracic levels.
Which of the following statements is true regarding caudal local anesthetics (LAs) in children?
A. The optimum concentration of bupivacaine is 0.125%–0.175%.
B. Patient height provides a better correlation than body weight in predicting spread of LA after a caudal block.