Which of the following medications warrant monitoring by the assessment referred to as the train-of-four? I. haloperidol II. aminosteroids III. dexmedetomidine IV. mivacurium

A. IV only
B. I, IV only
C. II, IV only
D. I, II, III only

?ANS: C
A. Incorrect response: See explanation C.
B. Incorrect response: See explanation C.
C. Correct response: The most common means of objective assessment of the degree of neuromuscular blockade in the ICU is peripheral nerve stimulation or "twitch monitoring." One of the most reliable means of performing this assessment is by the train-of-four. Four electrical impulses are delivered to a peripheral muscle group, usually the ulnar nerve at the wrist to produce adduction to the thumb.
The standard method is to apply a series of four stimuli in succession and compare the thumb movement in response to the first and fourth stimuli. The total absence of thumb movement is evidence of excessive neuromuscular blockade, whereas absence of a decrement in thumb contractions with repetitive nerve stimulation is evidence of inadequate blockade.
D. Incorrect response: See explanation C.