TOF 4/4 can have up to what percentage of receptors blocked?

TOF 4/4 can have up to what percentage of receptors blocked?

• A. 25%
• B. 50%
• C. 75%
• D. 90%

Answer: (C)

In this context, the key idea is how many receptors are blocked and how that shows up on a TOF test. Nondepolarizing neuromuscular blockers bind to nicotinic receptors in a competitive way. When about three-quarters of the receptors are blocked, you can still elicit four twitches that appear of equal strength—that is, a TOF pattern of 4/4 with no fade. The block is substantial enough to reduce the amplitude of each twitch, but not enough to cause differential waning among the four responses. Once blockade exceeds roughly 75%, fade appears and the pattern shifts away from 4/4. Therefore, TOF 4/4 can occur with up to about 75% receptor blockade.

In this context, the key idea is how many receptors are blocked and how that shows up on a TOF test. Nondepolarizing neuromuscular blockers bind to nicotinic receptors in a competitive way. When about three-quarters of the receptors are blocked, you can still elicit four twitches that appear of equal strength—that is, a TOF pattern of 4/4 with no fade. The block is substantial enough to reduce the amplitude of each twitch, but not enough to cause differential waning among the four responses. Once blockade exceeds roughly 75%, fade appears and the pattern shifts away from 4/4. Therefore, TOF 4/4 can occur with up to about 75% receptor blockade.