0071483446.pdf

(^280) CHAPTER 15 Nervous System Drugs
LOCAL ANESTHESIA
A local anesthetic (see chart) blocks pain at the site where the medication is
administered without affecting the patient’s consciousness. It is commonly used
for dental procedures, suturing of skin lacerations, short-term surgery at a local-
ized area, spinal anesthesia by blocking nerve impulses (nerve block) below the
insertion of the anesthetic, and diagnostic procedures such as lumbar punctures.
Local anesthetics are divided into two groups according to their basic chem-
ical structure. These are esters and amides. An ester is a chemical compound
formed from the reaction between an acid and an alcohol. Amides are an organic
chemical compound formed by reaction of an acid chloride, acid anhydride, or
ester with an amine. Amides have a lower incidence of causing an allergic reac-
tion than esters.
See local anesthetics listing provided in the Appendix. Detailed tables show
doses, recommendations, expectations, side effects, contraindications, and more;
available on the book’s Web site (see URL in Appendix).
SPINAL ANESTHESIA
Spinal anesthesia is a local anesthetic injected into the spinal column in the third
or fourth lumbar space to produce a regional neural block. If it is given too high,
the respiratory muscles could be affected and respiratory distress or failure could
result. There are 4 types of spinal anesthesia: subarachnoid block, epidural
block, the saddle block, and a caudal block.
A subarachnoid block is the injection into the subarachnoid space in the third
or fourth lumbar space to produce anesthesia.
Other Local Anesthetic Agents
Procaine (Novocaine) Short-acting (^1 / 2 to 1 hour)—ester, first synthetic local anesthetic,
relatively safe due to rapid metabolism in the plasma, fast onset-
short duration, not good for topical anesthesia
Cocaine Ester, only local anesthetic that is a vasoconstrictor, only local
anesthetic that produces euphoria, used by ENTs for surgical
procedures because it reduces pain and controls bleeding.
Tetracaine (Pontocaine) Long-acting—ester—used for spinal anesthesia and topical
Bupivicaine Long-acting—amide—can be cardiotoxic at high concentrations,
used for infiltration, epidural and nerve blocks.