title: The relationship between acceleromyographic train-of-four fade and single twitch depression.
abstract: BACKGROUND
  During offset of nondepolarizing neuromuscular block, a train-of-four (TOF) fade ratio of 0.70 or greater is considered to reliably indicate the return of single twitch height (T1) to its control value. Studies using mechanomyography or electromyography confirm this observation. The authors' impressions when using the acceleromyograph as a neuromuscular monitor did not support these results. Therefore, the authors studied the relation between T1 and the TOF ratio (when measured by acceleromyography) during recovery from neuromuscular block.
  
  
  METHODS
  Sixteen adult patients were studied. Anesthesia was induced with intravenous opioid plus 2.0-2.5 mg/kg propofol. Laryngeal mask placement or tracheal intubation was accomplished without the use of muscle relaxants. Anesthesia was maintained with nitrous oxide, desflurane (2.0-3.0%, end-tidal), and fentanyl. The response of the thumb to ulnar nerve stimulation was recorded with the TOF-Guard acceleromyograph (Organon Teknika BV, Boxtel, The Netherlands). TOFs were administered every 15 s. After final calibration, 0.15 mg/kg mivacurium was administered. No further relaxants were administered. T1 and the TOF ratio were then recorded until the TOF ratio had returned to its initial value (+/- 5%).
  
  
  RESULTS
  At a TOF ratio of 0.70 (during recovery of neuromuscular function), T1 averaged only 69 +/- 8% of control. At a TOF ratio of 0.90, T1 averaged 86 +/- 5% of control. To achieve 90% recovery of T1, a TOF ratio of 0.93 +/- 0.08 was required.
  
  
  CONCLUSIONS
  Assumptions regarding the relation between T1 and the TOF ratio derived from studies using mechanomyography and electromyography do not necessarily apply to observations obtained using acceleromyography.
authors.affiliation: Department of Anesthesiology, New York Medical College, Valhalla, New York, USA. akopman@rcn.com
authors.forename: Aaron F
authors.initials: AF
authors.lastname: Kopman
authors.forename: Monika M
authors.initials: MM
authors.lastname: Klewicka
authors.forename: George G
authors.initials: GG
authors.lastname: Neuman
mesh_terms: D000328:Adult; D000762:Anesthesia Recovery Period; D000768:Anesthesia, General; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D007546:Isoquinolines; D008297:Male; D008875:Middle Aged; D000077590:Mivacurium; D016343:Monitoring, Intraoperative; D009119:Muscle Contraction / Q000502:physiology*; D009213:Myography / Q000379:methods*; D009407:Nerve Block; D003473:Neuromuscular Nondepolarizing Agents; D013933:Thumb / Q000502:physiology; D014159:Transducers
chemical_list: D007546:Isoquinolines; D003473:Neuromuscular Nondepolarizing Agents; D000077590:Mivacurium