If one of four thumb twitches in the train-of-four (TOF) stimulation of the ulnar nerve can be elicited, how much suppression would there be for a single twitch?

If one of four thumb twitches in the train-of-four (TOF) stimulation of the ulnar nerve can be elicited, how much suppression would there be for a single twitch?

• A. 5 to 10
• B. 20 to 25
• C. 45 to 55
• D. 90 to 95

Answer: (D)

The key idea is how train-of-four (TOF) monitoring reflects the level of neuromuscular blockade. As blockade deepens, the twitches fade one by one. If only a single twitch can be elicited out of four, the remaining twitch is very small—roughly 5–10% of its normal strength. That translates to about 90–95% suppression of neuromuscular transmission at the nicotinic receptors. So, when one twitch remains, you’re looking at a profound block, not a mild one. The ulnar nerve test site (adductor pollicis) is particularly sensitive to nondepolarizing blockade, so this pattern indicates a high degree of suppression.

The key idea is how train-of-four (TOF) monitoring reflects the level of neuromuscular blockade. As blockade deepens, the twitches fade one by one. If only a single twitch can be elicited out of four, the remaining twitch is very small—roughly 5–10% of its normal strength. That translates to about 90–95% suppression of neuromuscular transmission at the nicotinic receptors. So, when one twitch remains, you’re looking at a profound block, not a mild one. The ulnar nerve test site (adductor pollicis) is particularly sensitive to nondepolarizing blockade, so this pattern indicates a high degree of suppression.