Local anesthetics

Question 1

How are local anesthetics metabolized?

Answer 1

Esters undergo hydrolysis by pseudocholinesterases found principally in plasma.

Amides undergo enzymatic biotransformation primarily in the liver.

Question 2

What local anesthetics where the lung can also metabolize? (3)

Answer 2

Lidocaine
Bupivacaine
Prilocaine

Question 3

What local anesthetic is least likely to produce sustained elevation in blood levels because of very rapid hydrolysis in the blood.

Answer 3

Chlorprocaine

Question 4

High risk for toxicity to esters include (3)

Answer 4

Atypical pseudocholinesterase
Liver disease
Neonates

Question 5

Is defined as the pH at which the ionized and unionized forms exist in equal concentrations.

Answer 5

pKa

Question 6

These symptoms appear within 24 hours of spinal
anesthesia and generally resolve within 7 days. The delayed onsetmay reflect an inflammatory etiology for these symptoms. They are seen most commonly with lidocaine spinal anesthesia and are rare with bupivacaine.

Answer 6

Transient neurologic symptoms

Patients having surgery in the lithotomy position appear to be at increased risk of neurologic symptoms following either spinal or epidural anesthesia.

Question 7

The mechanism of neural injury is thought to be that
nonhomogeneous distribution of spinally injected local anesthetic may expose sacral nerve roots to a high concentration of local anesthetic with consequent toxicity. Rare cases in the absence of microcatheters have also been described.

Answer 7

Cauda equina syndrome

Question 8

Which local anesthetic is associated with the risk of methemoglobinemia?

Answer 8

Prilocaine (more than 600 mg and benzocaine)

Question 9

What is the primary emergency treatment of methemoglobinemia?

Answer 9

Methylene blue 1-2 mg/kg