Biochemical and Circulatory Parameters during Purely Mental Stress

ABSTRACT. In order to evaluate biochemical and circulatory parameters during purely mental stress, 20 healthy medical students were studied before, during and at the end of an important written medical examination. Plasma catecholamines and diastolic blood pressure rose significantly during the examination, whereas systolic blood pressure did not change and heart rate declined. Continuous ECG recording in 12 of the subjects showed a high peak in heart rate at the start of the examination, quickly followed by a rapid decline to values seen on the previous day. It is suggested that in mental stress without physical effort, the enhanced sympathetic activity triggers an increase in parasympathetic activity which overrides the circulatory effects of the former. 1981 Association for the Publication of the Journal of Internal Medicin

Prediction of infarct size from serial CK determinations: Evaluation by clinical studies and computer simulation

To assess reduction of infarct size by therapeutic intervention, a high predictive accuracy is mandatory. The CK release in the circulation (CKr) was studied in 12 consecutive patients after uncomplicated myocardial infarction, admitted within 5 h after onset of symptoms. Despite improvement of existing methods, such as a more frequent sampling, CK-MB determination instead of total CK determination and use of a gamma-exponential instead of a log-normal curvefitting technique, the correlation between CK, predicted from measurements within 7 h after the start of CK rise and CKr calculated after completion of the CK curve remained poor. Computer simulations were done to investigate measurement errors as a cause of this failure. Normally distributed noise, with standard deviations ranging from 0.2% to 8.0% of peak CK-MB, was added to the first points of an ideal gamma-exponential CK-MB curve and predictions were made from these "noisy" points. A small noise already produced a great variation in prediction: 0.8% noise resulted in a deviation of predicted CKr from calculated CKrranging from -20 to + 6%. It is concluded that adequate prediction of infarct size from serial CK determinations in the first 7 h after onset of the CK rise must fail if the precision of the biochemical determination is not less than 0.4%