Effects of electromyographic activity on the accuracy of Narcotrend and bispectral index during sedation with dexmedetomidine

Abstract

Objective To investigate the effects of electromyographic activity on the accuracy of Narcotrend and bispectral index (BIS) during sedation with dexmedetomidine (Dex) under epidural anesthesia.Methods Sixteen patients scheduled for epidural anesthesia,9 males and 7 females,ASA Ⅰ or Ⅱ,aged 18 y-60 y,weighing 51 kg-93 kg,BMI 19.2 kg/m2-27.8 kg/m2 were prospectively studied.After the induction of epidural anesthesia,a loading dose of Dex was administered at 0.5 μg/kg per 15 min,followed by a continuous infusion at 0.4 μg ·kg-1 ·h-1,BIS and Narcotrend were monitored simultaneously,both values and EMG which was indicated on the BIS platform were recorded every minute.Sedation was assessed using the Observer's Assessment of Alterness/Sedation Scale (OAA/S) as well.The correlation between Narcotrend index (NTI)/BIS and EMG was analyzed.Results As the EMG activities above 50 dB elevated,BIS and NTI values were not increased (r=0.113,P=0.249;r=0.160,P=0.249).The misleading high BIS/NTI ≥85 occurred among 8 (50％ of all cases) and 9 (56％ of all cases) patients,respectively,at OAA/S ≤3.While there was no correlation (r=-0.046,P=-0.855) between BIS M (QR)87 (86-91) and EMG 34 (32-36),and there was no correlation (r=0.090,P=0.732) between NTI 90 (87-94) and EMG 41 (37-48),either.Conclusions During sedation with Dex under epidural anesthesia,high EMG activities do not result in BIS/NTI value increases.Impractical high BIS/NTI values are not caused by EMG elevation.Under sedation with Dex,the Narcotrend and BIS monitor are comparatively reliable with regard to their insusceptibility to increased EMG activity. Key words: Electromyographic activity; Consciousness monitors; Dexmedetomidine; Conscious sedation