title: Effect of propofol and remifentanil on a somatosensory evoked potential indicator of pain perception intensity in volunteers.
abstract: Somatosensory evoked potentials (SEPs) have been linked to noxious activation and stimulus intensity. In this exploratory study we investigated the impact of anaesthetic drugs on SEPs and pain ratings, to assess their applicability as an objective measure of the nociception/anti-nociception balance. Following institutional approval and written informed consent, 10 healthy adult volunteers were enrolled (29.5 ± 9.1 years, 63.0 ± 8.9 kg and 171.4 ± 7.2). Median nerve electrical stimulation was adjusted according to volunteers' sensitive, motor and painful thresholds (PT). Baseline SEPs were registered, and remifentanil and propofol administered using a stair scheme TCI. For each drug combination a 1.3×PT stimulus was administered, and volunteers evaluated pain intensity in a numerical rating scale (0-10). SEPs' amplitudes and latencies were normalized by the baseline values, reducing volunteers' intervariability. Stimulation currents varied between 6-52 mA (1.3×PT) and pain ratings between 0 and 9. Cortical SEPs latencies were decreased for higher stimulus intensities (P < 0.01), accompanied by increased pain ratings (P < 0.01). An individually adjusted/normalized ratio based on cortical SEPs amplitude and interpeak latency is proposed([Formula: see text]): [Formula: see text] and NSR were significantly correlated in three out of nine subjects, and [Formula: see text] and remifentanil Ce were significantly correlated in two (low number of evaluation points). [Formula: see text] was shown to decrease with increasing doses of propofol and remifentanil (P < 0.05). The proposed metric was depressed by anaesthetics and reflected pain evaluations. Further research is necessary to increase the number of volunteers and drugs' combination, to assess its applicability during surgically adequate anesthetic leves.
authors.affiliation: Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, sn, 4200-465, Porto, Portugal. ana.castro@fe.up.pt.|Centro de Investigação Clínica em Anestesiologia, Serviço de Anestesiologia, Hospital de Santo António, Centro Hospitalar do Porto, Largo Prof. Abel Salazar, 4099-001, Porto, Portugal. ana.castro@fe.up.pt.
authors.forename: Ana
authors.initials: A
authors.lastname: Castro
authors.affiliation: Centro de Investigação Clínica em Anestesiologia, Serviço de Anestesiologia, Hospital de Santo António, Centro Hospitalar do Porto, Largo Prof. Abel Salazar, 4099-001, Porto, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Amorim
authors.affiliation: Centro de Investigação Clínica em Anestesiologia, Serviço de Anestesiologia, Hospital de Santo António, Centro Hospitalar do Porto, Largo Prof. Abel Salazar, 4099-001, Porto, Portugal.|DCeT - Departamento de Ciências e Tecnologia, Universidade Aberta, Delegação do Porto, Rua do Amial, 752, 4200-055, Porto, Portugal.
authors.forename: Catarina S
authors.initials: CS
authors.lastname: Nunes
authors.affiliation: Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, sn, 4200-465, Porto, Portugal.|Centro de Investigação Clínica em Anestesiologia, Serviço de Anestesiologia, Hospital de Santo António, Centro Hospitalar do Porto, Largo Prof. Abel Salazar, 4099-001, Porto, Portugal.
authors.forename: Fernando Gomes
authors.initials: FG
authors.lastname: de Almeida
mesh_terms: D000328:Adult; D004305:Dose-Response Relationship, Drug; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D006993:Hypnotics and Sedatives / Q000008:administration & dosage; D008297:Male; D010147:Pain Measurement / Q000187:drug effects* / Q000379:methods*; D058748:Pain Perception / Q000187:drug effects / Q000502:physiology*; D010880:Piperidines / Q000008:administration & dosage*; D015742:Propofol / Q000008:administration & dosage*; D000077208:Remifentanil; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D006993:Hypnotics and Sedatives; D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol
keywords: Monitoring; Nociception; Pain; Somatosensory evoked potentials (SEPs); TIVA