title: Onset time for sevoflurane/nitrous oxide induction in adults is prolonged with increasing age.
abstract: Inhaled induction of anesthesia is occasionally used in adults. Using a modified vital capacity sevoflurane/nitrous oxide (N2O) inhaled induction, we evaluated the effect of increasing age on the onset time of anesthesia. Twenty patients, aged 26-65 yr, performed a vital capacity breath followed by regular tidal breathing from an anesthesia circuit primed with sevoflurane 8%/N2O/O2. The following values were recorded: time to loss of eyelash reflex (LOER); time to bispectral index < or =60 (BIS < or =60); expired fraction of sevoflurane at the time of induction, LOER and BIS < or =60. The mean times and 95% confidence intervals to LOER and BIS < or =60 were 54 s (37-70 s) and 175 s (143-207 s), respectively, and were significantly prolonged by aging (r = 0.65; P = 0.002). Times to LOER and BIS < or =60, predicted from the regression line, were 3.9 and 2 times longer in a 60-yr-old than in a 30-yr-old patient. The expired fraction of sevoflurane measured at time to LOER and BIS < or =60 decreases with increase in age. We conclude that inhaled induction with sevoflurane/N2O is dramatically prolonged with increased age.
authors.affiliation: Department of Anesthesiology, Miller School of Medicine at the University of Miami, Miami, Florida 33101, USA. mclewis@med.miami.edu
authors.forename: Michael C
authors.initials: MC
authors.lastname: Lewis
authors.forename: Ricardo I
authors.initials: RI
authors.lastname: Gerenstein
authors.forename: Gilbert
authors.initials: G
authors.lastname: Chidiac
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation; D004569:Electroencephalography; D005140:Eyelashes; D006801:Humans; D008738:Methyl Ethers; D008875:Middle Aged; D009609:Nitrous Oxide; D012018:Reflex / Q000187:drug effects; D000077149:Sevoflurane; D013997:Time Factors; D014797:Vital Capacity
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D009609:Nitrous Oxide