Question 1

A 34-year-old woman received a brachial plexus nerve block before undergoing surgical repair of carpal tunnel syndrome affecting her left wrist. A total of 40 ml of local anesthetic solution was used. Forty-five minutes after the nerve block was placed, the patient suffered a cardiac arrest. This is the local anesthetic most likely used:

A) Lidocaine
B) Mepivacaine
C) Etidocaine
D) Bupivacaine
E) Procaine

Bupivacaine

Accepted Answer

Bupivacaine has the highest cardiac toxicity of local anesthetics in use today.

Question 2

The following drug should NOT be administered to a patient with a plasma cholinesterase deficiency:&#10;A) Lidocaine&#10;B) Mepivacaine&#10;C) Etidocaine&#10;D) Bupivacaine&#10;E) Procaine

Accepted Answer

Procaine is an ester-type local anesthetic whose metabolism is primarily via plasma cholinesterase. The other local anesthetics listed are amides. Note that amides contain exactly two "i"s in their names, whereas esters contain only one.

Question 3

For the above 34-year-old woman experiencing local anesthetic-induced cardiac arrest, therapy with which of the following is most likely to aid resuscitation efforts?&#10;A) Saline infusion&#10;B) Dextrose solution&#10;C) Fat emulsion&#10;D) Magnesium sulfate&#10;E) Amino acids

Accepted Answer

Recent human case reports and canine studies indicate that intravenous lipid solution should be used as part of the resuscitation strategy in patients who suffer cardiac arrest after local anesthetic administration. Lipid emulsion acts to bind and sequester bupivacaine. In addition, fatty acids are also an important fuel source for cardiac tissue, whose metabolism is impaired by bupivacaine. Increasing availability of fatty acids helps to counteract this aspect of bupivacaine toxicity.

Deck 13: Local Anesthetics