Anaesthesia – can the patient feel the knife?

Anaesthetic agents are potentially dangerous drugs, and major patient complications can occur. If the patient is overdosed, death or major body organ damage can occur. Conversely, if the patient is under-dosed, patient awareness can occur. There is a narrow drug concentration “window” for both drug safety and anaesthetic efficacy, and the development of ways in which to monitor drug delivery concentration has been a major driver in anaesthetic agent safety research.

The Oxford invention has met this anaesthesia challenge by using modified statistical techniques to classify the physiological state of a human or animal subject. The classification monitors changes in the physiological state that occur over time either spontaneously or from external stimuli. Analysis of data obtained from anaesthetic trials has demonstrated the efficacy of the method for monitoring the depth of anaesthesia.

As well as using encephalograms the invention may be used advantageously with other forms of physiological data: electromyography to indicate muscle activity; analysis of images from magnetic resonance, computed tomography, X-ray and ultrasound; electrocardiography for blood pressure and blood oxygenation. The method also has many other applications including the monitoring of: consciousness, sleep, neuropathology, cerebral intoxication, cognitive state and muscle tremor.