Monitoring of the neuromuscular transmission by electromyography (I). Stability and temperature dependence of evoked EMG response compared to mechanical twitch recordings in the cat

Abstract

The stability over time and the effect of muscle temperature change were evaluated for the evoked compound EMG and for the mechanomyogram of the tibialis anterior muscle of 7 anaesthetized cats. Both EMG areas and amplitudes were recorded. During stimulation for 3 h with 0.1 Hz (one leg) and train-of-four (TOF) (the other leg), the EMG was stable while the mechanomyogram initially increased 35-50% in the first 7-8 min and then decreased 19-22% and 5-8% over the first and second 1.5-h period, respectively. During subsequent mean muscle temperature reduction to 28.8 degrees C (0.1 Hz) and 29.7 degrees C (TOF) and rewarming, an inverse linear relationship was found between temperature and both the EMG and the mechanomyogram. During temperature reduction EMG increased about 6% (areas) and 2% (amplitudes) per degrees C. During rewarming, parameters decreased about 4.5% and 2% per degrees C, respectively (P less than 0.05 comparing EMG areas during cooling and rewarming). TOF ratio of the EMG was not affected by temperature. A very large interindividual variation was observed for the effect of temperature on the mechanomyogram with changes ranging up to 15% per degrees C for some cats. TOF ratio of the mechanomyogram was reduced from 1.02 to 0.94 at lowest muscle temperature. It is concluded that the evoked EMG may be preferable to the mechanomyogram in cat experiments investigating the neuromuscular transmission.

Positive and negative staircase effect during single twitch and train-of-four stimulation: a laboratory study in dogs

“…A similar phenomenon has been observed in children and in cats: In children, Zhou et al [3] showed that an initial increase in T1 measured with AMG was followed by a decrease in T1 height. Using force measurements, Engbaek et al [4] showed that twitch amplitude in cats increased by 35.5 and 50.8 % during ST (0.1 Hz) and TOF stimulation, respectively, but then decreased to values as low as 60 % of baseline. Interestingly, we observed this decay in twitch amplitude in our dogs during TOF stimulation, but not with ST stimulation.…”

“…The staircase phenomenon is a self-limiting increase in the amplitude of evoked twitches that occurs during neuromuscular monitoring with mechanomyography (MMG) and with acceleromyography (AMG) in people [1][2][3] and domestic animals [4,5]. Changes in the magnitude of evoked twitches are used routinely in pharmacological studies to measure onset and offset of neuromuscular blocking agents (NMBAs).…”

Brief review: Neuromuscular monitoring: an update for the clinician

“…Whether integrated or peakto-peak amplitude is used to determine the power of the potential, the ability to use this method for routine monitoring is not influenced. 23 In general, EMG has been evaluated for most muscle sites of interest in FIGURE 1 Setup for mechanomyographic monitoring. The arm should be placed in a pre-molded cast, the thumb attached to a force transducer with an adequate pre-load.…”

Objektives Monitoring im klinischen Alltag

“…Vergleichende Untersuchungen haben gezeigt, dass sich das Elektromyogramm früher als die Kraftentwicklung erholt [4]. Anders als bei der Mechanomyographie fällt das EMG-Signal in den ersten min einer Messreihe ab [3].…”

“…Auch hier kann eine kurze Stabilisierungsphase und Neukalibration des Systems vorgenommen werden. Die Abnahme der EMG-Aktivität scheint zwar ein kontinuierlicher Prozess während der Untersuchung zu sein [4], eine zeitliche Zuordnung und eine Vorhersage über das Ausmaß ist aber nicht möglich. 70% des Referenzwerts erholt [10].…”