Which statement best describes the latency and duration when a mixture of chloroprocaine and bupivacaine is used for epidural anesthesia?

Which statement best describes the latency and duration when a mixture of chloroprocaine and bupivacaine is used for epidural anesthesia?

• A. Latency similar to chloroprocaine with duration similar to bupivacaine
• B. Latency shorter than chloroprocaine with duration longer than bupivacaine
• C. Latency shorter than chloroprocaine with duration similar to bupivacaine
• D. Latency longer than chloroprocaine with duration shorter than bupivacaine

Answer: (D)

Mixing a fast-onset, short-acting ester like chloroprocaine with a slow-onset, long-acting amide like bupivacaine creates a result where the onset is not as rapid as chloroprocaine alone, and the overall duration is curtailed compared to bupivacaine alone. Chloroprocaine’s quick start is tempered in the mixture by the slower onset of bupivacaine, so the latency ends up longer than chloroprocaine by itself. At the same time, chloroprocaine is rapidly metabolized and short-acting, so it shortens the overall duration of the mixture compared with bupivacaine alone. Thus, the mixture tends to have a longer latency than chloroprocaine and a shorter duration than bupivacaine.

Mixing a fast-onset, short-acting ester like chloroprocaine with a slow-onset, long-acting amide like bupivacaine creates a result where the onset is not as rapid as chloroprocaine alone, and the overall duration is curtailed compared to bupivacaine alone. Chloroprocaine’s quick start is tempered in the mixture by the slower onset of bupivacaine, so the latency ends up longer than chloroprocaine by itself. At the same time, chloroprocaine is rapidly metabolized and short-acting, so it shortens the overall duration of the mixture compared with bupivacaine alone. Thus, the mixture tends to have a longer latency than chloroprocaine and a shorter duration than bupivacaine.