We studied mid-latency auditory evoked potentials (MLAEP) during induction of general anaesthesia with ketamine 2 mg kg-1. MLAEP were recorded before, during and after induction of general anaesthesia on the vertex (positive) and mastoid (negative) positions. Latencies of the peak V, Na, Pa, Nb, P1 and amplitudes Na/Pa, Pa/Nb and Nb/P1 were measured. Fast-Fourier transformation was used to calculate power spectra of the MLAEP. In the awake state, MLAEP had large peak-to-peak amplitudes and a periodic waveform. Peak latencies remained within the normal range. Power spectra indicated high energy in the 30-40 Hz frequency range. After induction of general anaesthesia with ketamine, there was no change in latency of peaks V, Na, Pa, Nb, P1 and no apparent reduction in amplitudes Na/Pa, Pa/Nb and Nb/P1. In the power spectra, frequencies in the range of 30-40 Hz retained high energy. Amplitudes and latencies of MLAEP did not change during induction of general anaesthesia with ketamine. Primary processing of auditory stimuli in the primary auditory cortex seemed to be preserved under ketamine. Suppression of sensory (auditory) information processing must take place at a higher cortical level in a dissociative manner.

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In recent times preoperative anxiety is again discussed as an important influential factor for perioperative complications. The anaesthesiologist may be important to identify and control the patients' anxiety although his time while on premedication visit is rather limited. The present article deals with the different aspects of preoperative anxiety, argues about possible psychological and physiological characteristics of anxiety and describes conventionally used psychophysiological testing for the identification of anxiety. Referring to the literature, different therapeutical options are given. Psychological techniques for reducing and controlling preoperative anxiety might be an important topic for further research, especially as far as their influence on perioperative morbidity and mortality is concerned.

The effects of experimentally induced, severe coronary artery stenosis on regional changes in myocardial blood supply, cardiac function, and metabolism were studied in 14 dogs. The anterior interventricular branch of the left coronary artery (LAD) was constricted such that arterial inflow was reduced by 80%. Nine dogs were given enflurane in a concentration of 2.2 vol.% (1 MAC) in air, and five animals received no enflurane (controls). Regional myocardial blood supply was measured by the tracer microspheres technique, using 8-micron microspheres labelled with five different radioisotopes. Regional cardiac function (end-diastolic length of the muscle fibres = EDL; segmental shortening during systole = delta L) was estimated with the aid of two ultrasonic crystals which were placed in the subendocardial layer of the myocardium supplied by the LAD. Regional myocardial metabolism (oxygen consumption; lactate extraction) was evaluated from arterial and coronary venous blood samples. The latter were collected selectively from the region supplied by the LAD via the great cardiac vein. The results showed that, during severe coronary artery stenosis comparable to clinical conditions, apart from the known actions on systemic haemodynamics and contractility, enflurane had beneficial effects on regional myocardial variables. This was indicated by reduced regional contraction, measured as EDL and delta L; unchanged subendocardial blood flow without any redistribution; and improved lactate extraction in the ischaemic region.

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