Remifentanil reduces auditory and somatosensory evoked responses during isoflurane anaesthesia in a dose-dependent manner

• Published in: British journal of anaesthesia : BJA Vol. 76; no. 6; pp. 795 - 801
• Main Authors: Crabb, I, Thornton, C, Konieczko, K M, Chan, A, Aquilina, R, Frazer, N, Doré, C J, Newton, D E
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-06-1996; Oxford University Press; Oxford Publishing Limited (England)
• Subjects: Adjuvants, Anesthesia; Analgesics, Opioid - blood; Analgesics, Opioid - pharmacology; Anesthetics, Inhalation; Anesthetics. Neuromuscular blocking agents; Biological and medical sciences; Blood Pressure - drug effects; Dermatologic Surgical Procedures; Dose-Response Relationship, Drug; Double-Blind Method; Drug Administration Schedule; Evoked Potentials, Auditory - drug effects; Evoked Potentials, Somatosensory - drug effects; Heart Rate - drug effects; Humans; Intubation, Intratracheal; Isoflurane; Medical sciences; Neuropharmacology; Pharmacology. Drug treatments; Piperidines - blood; Piperidines - pharmacology; Remifentanil; Temazepam; Volatile compound; Human; Electrodiagnosis; General anesthetic; Auditory evoked potential; General anesthesia; Narcotic analgesic; Somatosensory evoked potential; Monitoring; Dose activity relation
• ISSN: 0007-0912; 1471-6771
• DOI: 10.1093/bja/76.6.795

We studied 60 patients during stable isoflurane anaesthesia (0.4 MAC) after premedication with temazepam. Patients were allocated randomly to one of three dose regimens of remifentanil: 1 microgram kg-1 i.v. over 1 min and an infusion of 0.2 microgram kg-1 min-1 (low dose); 2.5 micrograms kg-1 and 0.5 microgram kg-1 min-1 (medium dose); and 5 micrograms kg-1 and 1 microgram kg-1 min-1 (high dose). The auditory (AER) and median nerve somatosensory (SER) responses were elicited throughout, and recorded before and after tracheal intubation, and surgical incision, together with systolic and diastolic arterial pressure and heart rate. Venous blood concentrations of remifentanil were measured at the above times. After administration of remifentanil, Pa and Nb amplitudes of the AER increased at the low dose, remained constant at the medium dose and decreased at the high dose. This dose-related effect was linear and significant (P = 0.012, P = 0.05). Pa amplitude correlated inversely with remifentanil blood concentrations before and after intubation and incision (P = 0.002, P < 0.001, P < 0.001 and P < 0.001). In the SER, P15-N20 amplitudes decreased after administration of remifentanil (P < 0.001), whereas P25-N35 and N35-P45 amplitudes increased at all dose concentrations (P < 0.001 and P < 0.001). After intubation, P15-N20 and N35-P45 amplitudes increased at the low dose, did not change at the medium dose and decreased at the high dose (P = 0.001, P = 0.027). After remifentanil, systolic and diastolic arterial pressure and heart rate decreased in a linearly dose-related manner (P = 0.033, P < 0.001, P < 0.001). At all doses the three variables increased after intubation (P = 0.001, P < 0.001, P < 0.01), and systolic and diastolic arterial pressure increased after incision (P = 0.027, P = 0.039).