• A Angel, R H Arnott, D A Linkens, and C H Ting.
• Department of Biomedical Science, University of Sheffield, Western Bank, UK.
• Br J Anaesth. 2000 Sep 1;85(3):431-9.

AbstractPrimary 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.

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