MONITORING OF NEUROMUSCULAR-TRANSMISSION BY ELECTROMYOGRAPHY .2. EVOKED COMPOUND EMG AREA, AMPLITUDE AND DURATION COMPARED TO MECHANICAL TWITCH RECORDING DURING ONSET AND RECOVERY OF PANCURONIUM-INDUCED BLOCKADE IN THE CAT

The feasibility Of the compound electromyogram (EMG) was evaluated dur ing onset and recovery from pancuronium block in the tibialis anterior muscle of ten cats. The evoked EMG area, amplitude and duration of th e total response and of the major negative deflection were evaluated a nd compared to the mechanomyogram during 0.1 Hz and train-of-four (TOF ) stimulation. EMG areas and amplitudes were found to be linearly and similarly related to the mechanomyogram during onset and recovery. Slo pes of the regression lines ranged between 1.00-1.02 and between 1.10- 1.22 during onset and recovery, respectively, with high individual cor relation coefficients (> 0.95). The TOF ratio of the mechanomyogram wa s linearly related to the EMG TOF ratio during onset and to the square root of the EMG TOF ratio during recovery, with no differences betwee n EMG areas and amplitudes, suggesting a higher initial recovery of th e TOF ratio of the mechanomyogram during recovery. EMG duration increa sed as the level of block increased but was unsuitable for neuromuscul ar monitoring. Evaluation of the agreement between the two methods sho wed that the EMG may be from 15% below to 10% above the mechanomyogram during onset and from 40% below to 45% above the mechanomyogram durin g recovery, in spite of high correlation coefficients. In contrast, ag reement between EMG parameters was found to be high. In conclusion, EM G is more reliable than the mechanomyogram for evaluation of neuromusc ular transmission in the cat. EMG amplitudes and areas both reflect th e degree of neuromuscular blockade equally well.