<prompt> Train of four is characteristically used in concern withMalignant hypehermiaNon-depolarizing neuromuscular blockersMechanical ventilationTo check hemodynamic parameters  <response>: Train-of-four stimulation devotes four successive 200 - ms stimuli in 2 s 2 Hz. The twitches in a train-of-four pattern progressively fade as relaxation increases. The ratio of the responses to the first and fouh twitches is a sensitive indicator of nondepolarizing muscle paralysis. Disappearance of the fouh twitch represents a 75 block, the third twitch an 80 block, and the second twitch a 90 block. Clinical relaxation usually requires 75-95 neuromuscular blockade. Ref: KD Tripathi 8th ed. 