Infants have more CSF than adults, which leads to which spinal anesthesia effect compared with adults?

Infants have more CSF than adults, which leads to which spinal anesthesia effect compared with adults?

• A. Greater dose and longer duration
• B. Greater dose and shorter duration
• C. Smaller dose and longer duration
• D. Smaller dose and shorter duration

Answer: (B)

The key idea is how CSF volume and turnover affect intrathecal drug behavior. Infants have a larger intrathecal CSF space relative to their body size, so when a local anesthetic is placed in that space it becomes more diluted. To achieve the same level and density of block as in adults, a larger dose is needed. At the same time, infants have more rapid CSF turnover and absorption into the bloodstream, which tends to clear the drug from the intrathecal space faster, shortening how long the block lasts. So, compared with adults, infants typically require a greater dose to obtain an adequate spinal block, but the duration of that block is shorter.

The key idea is how CSF volume and turnover affect intrathecal drug behavior. Infants have a larger intrathecal CSF space relative to their body size, so when a local anesthetic is placed in that space it becomes more diluted. To achieve the same level and density of block as in adults, a larger dose is needed. At the same time, infants have more rapid CSF turnover and absorption into the bloodstream, which tends to clear the drug from the intrathecal space faster, shortening how long the block lasts. So, compared with adults, infants typically require a greater dose to obtain an adequate spinal block, but the duration of that block is shorter.