Select the true statement about spinal anesthesia in infants vs adults: dose and duration?

Select the true statement about spinal anesthesia in infants vs adults: dose and duration?

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

Answer: (B)

The key idea is how intrathecal drug behavior differs between infants and adults. In infants, the intrathecal space and CSF dynamics mean that a larger total dose of local anesthetic is needed to achieve a comparable sensory level to adults. The CSF volume per body size in infants is such that the drug becomes more dilutes and spreads differently, so a bigger amount is required to reach the same height of block. At the same time, once in the intrathecal space, infants clear/localize the drug more rapidly into the systemic circulation because of higher spinal blood flow and faster uptake, so the duration of the block tends to be shorter than in adults. Thus, infants generally require a greater dose to achieve a desired level, but the anesthetic effect lasts for a shorter period compared with adults.

The key idea is how intrathecal drug behavior differs between infants and adults. In infants, the intrathecal space and CSF dynamics mean that a larger total dose of local anesthetic is needed to achieve a comparable sensory level to adults. The CSF volume per body size in infants is such that the drug becomes more dilutes and spreads differently, so a bigger amount is required to reach the same height of block.

At the same time, once in the intrathecal space, infants clear/localize the drug more rapidly into the systemic circulation because of higher spinal blood flow and faster uptake, so the duration of the block tends to be shorter than in adults.

Thus, infants generally require a greater dose to achieve a desired level, but the anesthetic effect lasts for a shorter period compared with adults.