Train-of-Four
Also written as: TOF — Train-of-Four
A neuromuscular monitoring technique that delivers four successive electrical stimuli to a peripheral nerve to assess the degree of neuromuscular blockade and adequacy of reversal.
Full Definition
Train-of-four (TOF) monitoring applies four 2-Hz supramaximal stimuli to a peripheral nerve (commonly the ulnar nerve) and counts the number of visible or felt muscle twitches. The TOF ratio—the amplitude of the fourth twitch divided by the first—quantifies residual blockade; a ratio of 0.9 or above is considered safe for extubation. In dental anesthesiology, TOF monitoring is indispensable whenever neuromuscular blocking agents are used, ensuring patients are not extubated with residual paralysis. Editors should hyphenate 'train-of-four' when used as a compound modifier and expand the abbreviation TOF on first mention.
Usage
Usage note: Always hyphenate 'train-of-four' as a compound noun or modifier. 'TOF count' (0–4 twitches) is distinct from 'TOF ratio' (0–1.0 numerical value).
In Context
- "Train-of-four monitoring confirmed a ratio of 0.95 before the patient was extubated in the operating suite." — Anesthesia record
- "The anesthesiologist documented train-of-four count and ratio at 15-minute intervals throughout the procedure." — Intraoperative monitoring log