Psychosomatic Medicine 35:112-120 (1973)
© 1973 American Psychosomatic Society

Comparison of Pressor and Adrenergic Responses Derived from Direct and Indirect Methods of Cardiovascular Testing

¹ Section of Hypertension and Clinical Pharmacology, Department of Medicine, University of Pittsburgh School of Medicine Pittsburgh, Pennsylvania; Trainee in Clinical Pharmacology, supported by training grant HE 5467 from the National Heart and Lung Institute. Present address: Department of Internal Medicine, University of Utah Medical Center, Salt Lake City, Utah
² Section of Hypertension and Clinical Pharmacology, Department of Medicine, University of Pittsburgh School of Medicine Pittsburgh, Pennsylvania

Address for reprint requests: Alvin P. Shapiro, MD, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213.

This study in ten healthy volunteers compared the influence of direct vs. indirect (i.e., invasive vs. noninvasive) methods of measurement on cardiovascular responses to noxious stimuli. Several biochemical correlates of adrenergic stimulation also were determined (i.e., urinary catechols, plasma-free fatty acids, and cortisol). The study was designed so that the effects of "novelty" in the experiment also could be evaluated by analyzing the data for the order of testing as well as the type of testing. The data indicated a greater urinary excretion of epinephrine prior to testing on the first procedural day independent of whether the testing was done by direct or indirect techniques. There were no other differences related to the order of testing. No differences were noted in the cardiovascular responses or the biochemical measurements related to whether the testing was done by direct or indirect techniques, with the possible exception of a greater rise in free fatty acids with direct procedures which could not be explained. As in our previous studies, the degree of response of the biochemical correlates of adrenergic stimulation did not correlate with the magnitude of cardiovascular response.

Thus within the limits defined by the type of volunteer subject used here, the stimulus responses were not affected by the type of methodology used. However, a novelty effect was shown in catecholamine excretion, affecting epinephrine but not norepinephrine. The lack of correlation between the degree of response of the cardiovascular system and the degree of activation of the adrenergic system as indicated biochemically, lends further support to the concept that the former is determined by the intrinsic vascular sensitivity of the patient whereas the latter indicates primarily his degree of emotional arousal.