Local anesthetics are essential agents used in current surgical practice. Which of the following statement(s) is/are true concerning the use of local anesthetic agents

b. Bupivacaine is noted for a slow onset but long duration

c. The addition of epinephrine to a local anesthetic agent will both lower the toxicity and increase the duration of local anesthesia

Local anesthetics constitute a class of drugs which produce temporary blockage of nerve conduction by binding to neuronal sodium channels. Adverse consequences associated with the use of local anesthetics fall into three categories: acute central nervous system toxicity due to excessive plasma concentration, hemodynamic and respiratory consequences due to excessive conduction block of the sympathetic or motor nerves, and allergic reactions. Whenever a local anesthetic has been injected, there may be inadvertent intravascular injection or an overdose of the drug due to rapid uptake from the tissues. All may produce seizures. Complications can be minimized by aspirating prior to injection to avoid intravascular injection and limiting the doses to the safe range. When local anesthetics are administered for a spinal or epidural block, there will be a progressive blockade of the sympathetic nervous system which will produce systemic vasodilatation. If the block travels along the thoracolumbar region, a sympathetic blockade will result in profound systemic vasodilatation and bradycardia with resultant hypotension.

 Local anesthetics are divided into two groups: esters and amides. Most commonly used agents, the amides, include lidocaine and bupivacaine. Lidocaine is noted for a fast onset of action but a short duration whereas bupivacaine has a slower onset with the duration lasting for four to 12 hours. The addition of epinephrine (100 µg) will lower the toxicity and increase the duration of the local anesthetic.