Monday Lecture: Local Anesthetics

Question 1

Describe how local anesthetics can be administered.

Answer 1

• Into subcutaneous tissues (local area numbness)
• Into subcutaneous tissues near a nerve (nerve block)
• Into CSF (spinal block)
• Into epidural space
• Mucosa/topical application

Question 2

How are amides practically different from the ester class?

Answer 2

• The amide bond makes the molecule last longer.

* They have less allergic potential.

Question 3

Explain how pKa affects the onset of local anesthetics.

Answer 3

Local anesthetics need to be un-ionized to enter cells. Thus, those with pKas that are lower are more likely to be neutral at physiologic pH and work faster. Higher pH means slower onset.

Question 4

Review the effect of lipid solubility on the duration of action.

Answer 4

Higher lipid solubility means greater duration.

Question 5

The agents that have high protein binding have _____________.

Answer 5

long duration of action

Question 6

Go through the mnemonic for absorption.

Answer 6

BICEPSS: the decreasing order of vascularity

1) Blood
2) Intercostal
3) Caudal
4) Epidural
5) Perivascular
6) Spinal
7) Subcutaneous

Question 7

What is LAST?

Answer 7

Local Anesthetic Systemic Toxicity

Question 8

Describe the symptoms of LAST.

Answer 8

Neuro: 
•Circumoral numbness
• Tinnitus
• Seizure
• Lightheadedness 
•Visual changes 

Cardiovascular:
•Vasodilation
•Cardiac depression
•Hypotension

Question 9

Review the LAST management protocol.

Answer 9

• Stop injection of local anesthetic
• Maintain airway
• Start IV if not present already
• Give benzodiazepines for seizure
• Treat hypotension and arrhythmias
• Inject lipid emulsion