title: Changes in the photoplethysmogram with tracheal intubation and remifentanil concentration.
abstract: Autonomic sympathetic activation, for instance following noxious stimuli, decreases the size and flattens the shape of the photoplethysmographic peripheral pulse waveform. We report a simple measure of the waveform shape, the ratio of mean-to-peak wave amplitude, for measuring nociception level during general anaesthesia. Fifty participants, anaesthetised with propofol and remifentanil, were randomly allocated to one of three different remifentanil effect-site concentrations (1, 3 and 5 ng.ml(-1) ). Tracheal intubation increased the mean (SD) plethysmographic ratio from 0.38 (0.06) to 0.48 (0.04), p = 2.6 × 10(-16) . The mean (SD) ratios following intubation at remifentanil effect-site concentrations of 1 ng.ml(-1) , 3 ng.ml(-1)  and 5 ng.ml(-1) , were 0.49 (0.03), 0.48 (0.03) and 0.45 (0.04), respectively. Remifentanil therefore suppressed changes in the mean-to-peak ratio caused by tracheal intubation (p = 0.006). The ratio of the mean-to-peak plethysmographic amplitude may represent a simple measure of the balance of autonomic sympathetic and parasympathetic activity under general anaesthesia, and its performance following intubation was significantly different from peak amplitude (p = 0.046).
authors.affiliation: The Key Laboratory of Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrument Science, Zhejiang University, Zhejiang, China.
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: X
authors.initials: X
authors.lastname: Chen
authors.forename: S
authors.initials: S
authors.lastname: Ye
authors.forename: Y
authors.initials: Y
authors.lastname: Feng
authors.forename: C
authors.initials: C
authors.lastname: Huang
authors.forename: L
authors.initials: L
authors.lastname: Hou
authors.forename: J
authors.initials: J
authors.lastname: Liu
authors.forename: H
authors.initials: H
authors.lastname: Chen
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000768:Anesthesia, General / Q000379:methods; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal; D008297:Male; D017156:Photoplethysmography; D010880:Piperidines / Q000494:pharmacology*; D015742:Propofol; D000077208:Remifentanil
chemical_list: D018686:Anesthetics, Intravenous; D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol