Stabilization and stability of twitch force during mechanomyography of the adductor pollicis muscle.
OBJECTIVE
In order to study the stabilization time, the increase in twitch force during stabilization and the maintenance of stability during mechanomyography of the adductor pollicis muscle, neuromuscular function was monitored in 20 patients anaesthetized without the use of a neuromuscular blocking agent. The effect of the type of stimulation (single twitch [ST; 0.1 Hz], or train-of-four [TOF; 4 stimuli at 2 Hz, repeated every 12 s]) on these variables was studied. When applying TOF stimulation, the variables were also investigated for the TOF percentage [quotient of fourth and first twitch of a TOF stimulus x 100%].


METHODS
Two groups of ten patients were monitored with either ST or TOF stimulation. Measurements continued for at least 45 minutes. Multiple linear regression analysis was applied to examine the effect of stimulation on the stabilization time and the increase in twitch force.


RESULTS
According to our criteria for stability, we found that the stabilization time did not differ for ST (13.7 [10.2] min; mean [sd]) and TOF stimulation (18.1 [9.6] min) (p > 0.10). Stabilized twitch forces were larger during TOF than during ST stimulation (134% [19] and 113% [11]; p = 0.01). In both groups of stimulation, six patients showed an interruption of stability. The TOF percentage was stable throughout the measurement period in all patients.


CONCLUSIONS
Stabilization of twitch force takes too long for many studies of neuromuscular function in the clinical research setting. Therefore, we do not recommend its routine use when performing mechanomyography of the adductor pollicis muscle.
van Santen
G
G
Research Group for Experimental Anesthesiology and Clinical Pharmacology, University of Groningen, The Netherlands.
Fidler
V
V
Wierda
J M
JM
D000328:Adult; D000367:Age Factors; D001696:Biomechanical Phenomena; D004558:Electric Stimulation; D005260:Female; D017408:Guidelines as Topic; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology; D009126:Muscle Relaxation / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009213:Myography / Q000379:methods; D009468:Neuromuscular Diseases / Q000175:diagnosis*; D012016:Reference Values; D013997:Time Factors