title: Effect of surface electrode position on the compound action potential evoked by ulnar nerve stimulation during isoflurane anaesthesia.
abstract: The effect of surface electrode positioning on the evoked compound action potential was studied during isoflurane anaesthesia without neuromuscular block. In 20 ASA I-II patients (age 36-50 yr), the response after supramaximal ulnar nerve stimulation was analysed with a neuromuscular relaxation monitor (Relaxograph, Datex) and with a memory recorder. Seven pairs of surface recording electrodes were compared: (1) adductor pollicis muscle vs second finger; (2) adductor pollicis m. vs first finger; (3) first dorsal interosseus m. vs second finger; (4) abductor digiti minimi m. vs fifth finger; (5) adductor pollicis m. vs second dorsal metacarpal; (6) abductor digiti minimi m. vs fourth dorsal metacarpal; (7) thenar vs hypothenar. Steady biphasic response was recorded with electrode pairs 1-4. Marked variation and low amplitude existed at pairs 5-7. Peak-to-peak amplitude at pair 3 was the greatest (12.5 (SD 3.7) mV) compared with pair 4 (9.4 (SD 2.0) mV) and pair 1 (8.5 (SD 2.0) mV). A close correlation between the amplitudes and integrated areas was found. The first dorsal interosseus muscle response was optimal and the electrodes were simple to fix; this site may be recommended for clinical monitoring.
authors.affiliation: Helsinki University Central Hospital, Department of Anaesthesia, Finland.
authors.forename: I
authors.initials: I
authors.lastname: Kalli
mesh_terms: D000769:Anesthesia, Inhalation; D004558:Electric Stimulation; D004566:Electrodes; D004576:Electromyography / Q000295:instrumentation; D005071:Evoked Potentials / Q000502:physiology; D006225:Hand / Q000502:physiology*; D006801:Humans; D007530:Isoflurane; D008875:Middle Aged; D014459:Ulnar Nerve / Q000502:physiology*
chemical_list: D007530:Isoflurane