Changes in auditory evoked potential index and bispectral index produced by treatment of hypotension with ephedrine or phenylephrine during induction of general anesthesia

Abstract

Objective To investigate the changes in auditory evoked potential index(AAI)value and bispectral index(BIS)value produced by treatment of hypotension with ephedrine or phenylephrine during induction of general anesthesia.Methods Seventy-five ASA Ⅰ or Ⅱ patients of both sexes aged 30-50 yr with body mass index ＜ 30 kg/m2 underwent elective abdominal surgery under general anesthesia.Anesthesia was induced with 8%sevoflurane,midazolam 0.1 mg/kg and fentanyl 3 μg/kg.Tracheal intubation was facilitated with succinylcholine 2 mg/kg.Anesthesia was maintained with sevoflurane inhalation.BIS value was maintained at 40-50 and AAI value at 20-30 by adjusting the concentration of sevoflurane.When the desired level of BIS value and AAI value was reached during induction of anesthesia,hypotension(MAP ＜ 80 % of the baseline)was treated with intravenous ephedrine 0.1 mg/kg(group E,n = 25)or phenylephrine 2 mg/kg(group P,n = 25)or 6% HES(130/0.4)10 ml/kg(group C,n = 25)at random.MAP,HR,BIS value and AAI value value were recorded before(T0)and at 2,5,7,10 min after fluid or vasoactive agent administration(T1-4).Results MAP significantly increased after treatment at T1-4 as compared with MAP at To in all 3 groups.BIS and AAI values were significantly increased after administration of ephedrine at T3,4 as compared with MAP at To in group E.There were no significant differences in BIS and AAI values before and after administration of phenylephrine and 6% HES in group P and C.Con-clusion Treatment of hypotension with ephedrine during induction of general anesthesia can increase BIS and AAI and decrease the depth of anesthesia but phenylephrine cannot. Key words: Ephedrine; Deoxyepinephrine; Electroencephalography; Evoked potentials,auditory; Anesthesia,general