STIMULUS FREQUENCY IN THE DETECTION OF NEUROMUSCULAR BLOCK IN HUMANS (REPRINTED FROM BRIT. J. ANAESTH., VOL 42, PG 967, 1970)

Study of the Literature on the physiology of neuromuscular transmissio n suggested two new methods of assessing the degree of neuromuscular b lock in the human subject. These were, first, a comparison of the heig ht of the recorded twitch tensions developed in response to repeated s ingle stimuli applied at differing frequencies and, second, examinatio n of the extent of reduction in amplitude of twitch tensions developed in response to a short train of four stimuli. In assessing the first method the use of three frequencies of stimulation was tried (i.e., 0. 1 Hz (c.p.s.), 0.3 Hz and 1.0 Hz). It was found that as the frequency of stimulation was increased there was reduction in the amplitude of t he recorded twitch response in curarized subjects, and that this reduc tion appeared to depend on the degree of curarization. In assessing th e second method a short train of four stimuli at 2 Hz was used, and it was found that there was a progressive fade of successive recorded me chanical twitch responses in curarized subjects which again appeared t o depend on the degree of curarization. It is suggested that the ampli tude of the twitch response at a higher frequency expressed as a perce ntage of that at the slower rate, and the last response of the train o f four expressed as a percentage of the first may be useful in measuri ng degree of neuromuscular block in man.