title: Duration of control stimulation does not affect onset and offset of neuromuscular blockade at the corrugator supercilii muscle measured with phonomyography or acceleromyography.
abstract: OBJECTIVE
  Phonomyography (PMG) is a novel technique for measuring neuromuscular blockade (NMB). The effect of the duration of control stimulation on the onset and duration of blockade was investigated using PMG and acceleromyography (AMG).
  
  
  METHODS
  After induction of anesthesia, a microphone was placed above the middle portion of the left eyebrow, and an acceleromyographic probe was placed above the middle portion of the right eyebrow. Twenty patients were randomized to receive bilateral, single-twitch, facial nerve stimulation (0.1 Hz, 20 mA) with three minutes (n = 10) or ten minutes (n = 10) of supramaximal stimulation before mivacurium 0.2 mg.kg(-1) was administered. Onset, maximum effect, and offset of NMB were measured.
  
  
  RESULTS
  Using PMG, lag time, onset time, maximum effect, and time to reach 75% of control twitch height (mean +/- SD) were 36 +/- 27 sec, 136 +/- 35 sec, 89 +/- 10%, and 12.1 +/- 4.5 min, respectively, after three minutes of control stimulation and were 40 +/- 22 sec, 122 +/- 40 sec, 93 +/- 3%, and 12.4 +/- 4.9 min, after ten minutes. Using AMG, the values were 38 +/- 23 sec, 106 +/- 28 sec, 79 +/- 6%, and 14.3 +/- 5.9 min, respectively, after three minutes and were 34 +/- 22 sec, 106 +/- 28 sec, 76 +/- 10%, and 14.9 +/- 3.7 min, after ten minutes. Compared to PMG, AMG revealed significant bias for onset time (-30 sec), maximum effect (-16%) and time to reach 75% of control twitch height (1.5 min), with wide limits of agreement of 66 sec, 22%, and 5.6 min, respectively.
  
  
  CONCLUSIONS
  The duration of control stimulation did not influence the time course of blockade measured by either method. Three minutes of supramaximal stimulation is sufficient to measure pharmacodynamic parameters. AMG measures a shorter onset and longer recovery time and reduced anesthesiology the maximum effect compared to PMG.
authors.affiliation: Department of Anesthesia, Neuromuscular Research Group, Centre Hospitalier de l'Université de Montréal (CHUM) and the Department of Anesthesiology, Université de Montréal, Montréal, Québec, Canada. thomashemmerling@hotmail.com
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Hemmerling
authors.forename: François
authors.initials: F
authors.lastname: Donati
authors.forename: Denis
authors.initials: D
authors.lastname: Babin
authors.forename: Pierre
authors.initials: P
authors.lastname: Beaulieu
mesh_terms: D000328:Adult; D000368:Aged; D000768:Anesthesia, General; D003627:Data Interpretation, Statistical; D004558:Electric Stimulation; D005154:Facial Nerve / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects*; D009213:Myography / Q000379:methods*; D009466:Neuromuscular Blocking Agents; D012815:Signal Processing, Computer-Assisted; D013016:Sound
chemical_list: D009466:Neuromuscular Blocking Agents