Why are ester local anesthetics not used for intravenous regional blocks?

Why are ester local anesthetics not used for intravenous regional blocks?

• A. They are too long acting
• B. They cause more systemic toxicity
• C. They are rapidly hydrolyzed by plasma esterases
• D. They are not potent enough

Answer: (C)

In intravenous regional anesthesia the drug must stay active in the isolated limb for the duration of the procedure and remain effective after the tourniquet is released. Ester local anesthetics are quickly broken down by plasma esterases, so their action is short and often unreliable for a Bier block. Once any absorbed drug enters the systemic circulation, it is rapidly hydrolyzed, leading to very brief analgesia and poor postoperative pain control. Amide local anesthetics, being more resistant to plasma hydrolysis, provide a longer, more predictable block suitable for IV regional anesthesia.

In intravenous regional anesthesia the drug must stay active in the isolated limb for the duration of the procedure and remain effective after the tourniquet is released. Ester local anesthetics are quickly broken down by plasma esterases, so their action is short and often unreliable for a Bier block. Once any absorbed drug enters the systemic circulation, it is rapidly hydrolyzed, leading to very brief analgesia and poor postoperative pain control. Amide local anesthetics, being more resistant to plasma hydrolysis, provide a longer, more predictable block suitable for IV regional anesthesia.