Local Anesthesia
Types of Local Anesthetics
-
Esters (metabolized by plasma cholinesterase)
- Cocaine (out of date)
- Benzocaine
- Procaine
- Tertracaine
-
Amides (metabolized by cytochrome p-450)
- Lidocaine
- Bupivacaine
- Mepivacaine
- Prilocaine
- Ropivacaine
Local Anesthesia toxicity, and adjuncts
Local Anesthetics
- Mechanism of Action: Reversibly blocking sodium channels to prevent depolarization.
- Lipid Solubility: Potency, plasma protein binding determines, duration of action of local anesthetics.
- Addition of Vasoconstrictor: Prolongation of anesthetic action, decreased risk of toxicity, and decrease in bleeding from surgical manipulation.
Applications of Local Anesthesia
- Nerve block: (e.g., dental and other minor surgical procedures)
- Topical application: To skin for analgesia (e.g., benzocaine) or mucous membranes (for diagnostic procedures)
- Spinal & epidural anesthesia:
- Local infiltration: At end of surgery to produce long-lasting post-surgical analgesia (reduces need for narcotics)
- I/V: For control of cardiac arrhythmias (e.g., lidocaine for ventricular arrhythmias)
Choice of Local Anesthetics
- Onset
- Duration
- Sensory vs. motor block
- Potential for toxicity
All must be preservative free.