Somatosensory evoked potentials for closed-loop control of anaesthetic depth using propofol in the urethane-anaesthetized rat.
Primary somatosensory cortical mass responses have been shown to exhibit dose-dependent changes in latency when general anaesthetics are administered. Here we describe a system in which the latency of evoked responses was measured automatically in real time in five animals. Latency changes were used to operate a closed-loop control of propofol delivery by intravenous infusion. The system attempted to induce and maintain a 1 ms increase in evoked response latency; this was reversed when infusion was discontinued. Allowing for the rapid and large biological fluctuations in the evoked response, this was achieved successfully. The system maintained a mean increase in latency of 1.27 (SD 0.42) ms. The mean statistical dispersion index of data obtained during the controlled period was 1.23 (0.3); in an ideal controllable system it approximates to 1. Such a system may provide a means for the automatic delivery of anaesthetics.
Angel
A
A
Department of Biomedical Science, University of Sheffield, Western Bank, UK.
Arnott
R H
RH
Linkens
D A
DA
Ting
C H
CH
D000764:Anesthesia, Closed-Circuit; D000771:Anesthesia, Intravenous / Q000379:methods*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D016503:Drug Delivery Systems; D001330:Electronic Data Processing; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects*; D005260:Female; D007262:Infusions, Intravenous; D015742:Propofol / Q000008:administration & dosage*; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects*; D014520:Urethane
D018686:Anesthetics, Intravenous; D014520:Urethane; D015742:Propofol