British journal of anaesthesia
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Clinical Trial
Effect of surface electrode position on the compound action potential evoked by ulnar nerve stimulation during isoflurane anaesthesia.
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. ⋯ 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.
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We have measured whole blood concentrations and pharmacokinetics of propofol administered as a constant rate infusion during cardiac surgery. Ten patients undergoing elective cardiac surgery involving cardiopulmonary bypass (seven myocardial revascularization and three aortic valve surgery) received a continuous infusion of propofol 4 mg kg-1 h-1 to supplement alfentanil analgesia. ⋯ A concentration greater than 1 microgram ml-1 was achieved within 15 min of starting the infusion and remained constant throughout surgery. Volume of distribution, clearance and terminal half-life were similar to those found in non-cardiac patients.