Which statement about dibucaine numbers is true?

Which statement about dibucaine numbers is true?

• A. Dibucaine is an ester-type local anesthetic
• B. A dibucaine number of 20 is normal
• C. The dibucaine number represents the quantity of normal pseudocholinesterase
• D. Neuromuscular blockade with succinylcholine would last several hours in a patient with a dibucaine number of 80

Answer: (C)

The dibucaine number gauges how much normal pseudocholinesterase (butyrylcholinesterase) activity is present by measuring the percent of the enzyme inhibited by dibucaine. Normal enzyme is inhibited about 80% by dibucaine, so a normal dibucaine number is around 80. A lower dibucaine number indicates an atypical enzyme with much less inhibition, which is associated with prolonged duration of succinylcholine. Therefore, the statement that the dibucaine number represents the quantity of normal pseudocholinesterase is the best description: a higher number means more normal enzyme activity, and a value around 80 suggests normal duration for succinylcholine. The other points are incorrect for this concept: dibucaine is not an ester-type local anesthetic, a normal dibucaine number is not 20, and a number of 80 would not predict several hours of blockade.

The dibucaine number gauges how much normal pseudocholinesterase (butyrylcholinesterase) activity is present by measuring the percent of the enzyme inhibited by dibucaine. Normal enzyme is inhibited about 80% by dibucaine, so a normal dibucaine number is around 80. A lower dibucaine number indicates an atypical enzyme with much less inhibition, which is associated with prolonged duration of succinylcholine. Therefore, the statement that the dibucaine number represents the quantity of normal pseudocholinesterase is the best description: a higher number means more normal enzyme activity, and a value around 80 suggests normal duration for succinylcholine. The other points are incorrect for this concept: dibucaine is not an ester-type local anesthetic, a normal dibucaine number is not 20, and a number of 80 would not predict several hours of blockade.