The construction and evaluation of a device for mechanomyography in anaesthetized Göttingen minipigs.
OBJECTIVE
To devise a method for assessing evoked muscle strength on nerve stimulation [mechanomyography (MMG)] in the anaesthetized minipig.


METHODS
Prospective observational.


METHODS
Sixty male Göttingen minipigs weighing 10.5-26.0 kg.


METHODS
After cadaveric studies, a limb fixation device was constructed which allowed the twitch responses of the pelvic limb digital extensor muscles to be measured by force-displacement transduction in response to supramaximal train-of-four (TOF) stimulation of the common peroneal nerve. The device was tested in 60 minipigs weighing 10.5-26.0 kg positioned in dorsal recumbency.


RESULTS
The technique recorded the MMG of the common peroneal-pelvic limb digital extensor nerve-muscle unit for up to 12 hours during which twitch height remained constant in 18 animals in which single twitch duration was <300-500 ms. In 42, in which twitch duration was >300-500 ms, 2 Hz nerve stimulation caused progressive baseline elevation (reverse fade) necessitating a modified signal capture method for TOF ratio (TOFR) computation. However, T1 was unaffected. The mean (range) of the TOFR in pigs with reverse fade was 1.2 (1.1-1.3).


CONCLUSIONS
The technique allowed MMG recording in unparalysed pigs in response to TOF nerve stimulation and revealed a hitherto unreported complication of MMG monitoring using TOF in animals: reverse fade. This complicated TOFR calculation.
Department of Veterinary Clinical Studies, Easter Bush Veterinary Centre, Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Roslin, Midlothian, UK. e.clutton@ed.ac.uk
R Eddie
RE
Clutton
Kosala
K
Dissanayake
Holly
H
Lawson
Keith
K
Simpson
Adrian
A
Thompson
Michael
M
Eddleston
D000818:Animals; D002102:Cadaver; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D009213:Myography / Q000295:instrumentation / Q000379:methods / Q000662:veterinary*; D013552:Swine; D013556:Swine, Miniature / Q000502:physiology*