WARUM BRAUCHEN WIR EINE OBJEKTIVIERUNG DER 'NARKOSETIEFE'?

Despite intensive efforts, we still do not have generally accepted definition of the 'depth of anaesthesia'. While Prys-Roberts considers the loss of consciousness during general anaesthesia to be an all or nothing event, Jones is of the opinion that general anaesthesia can be subdivided into several stages depending upon the presence of intraoperative awareness and/or amnesia. Definition of the 'depth of anaesthesia' by using auxiliary constructs, such as MAC and ED₅₀ is controversial because muscle activity does not represent a measure of cerebral activity during anaesthesia. The applicability of the EEG and the parameters derived from it as the sole measure of 'depth of anaesthesia' is limited by the fact that modern anaesthesia is usually performed by administering a combination of several drugs with differing action profiles whose effects on the cerebral activity mutually influence each other. More recent investigations, however, seem to indicate that a combination of clinical signs and several parameters of cerebral activity may solve the problem of measuring the 'depth of anaesthesia' in the future.