Pressor tests in clinical pharmacology: response morphology heterogeneity.

Heart rate, blood pressure and venous plasma catecholamine responses to passive upright tilt, immobile erect standing, upright sitting, immersion of hand or foot in cold water, isometric handgrip and delayed auditory feedback were assessed in young healthy volunteers. Each of the tests was characterized by its own typical response morphology. Postural stress caused mainly a rise in heart rate and diastolic blood pressure with little change in systolic blood pressure. The cold pressor test caused a rapid rise in heart rate, systolic and diastolic blood pressure which then was attenuated on further exposure to cold. Isometric handgrip caused the largest pressor responses in linear fashion relative to time. Protracted isometric handgrip (i.e., 5 rather than 3 min) seemed to add psychological stress to the response profile. Delayed auditory feedback caused a less well structured rise in heart rate, systolic and diastolic blood pressure. The postural tests were the most powerful stimuli for venous plasma catecholamines. For all further tests, the catecholamine responses were in general quite small. Therefore, the tests should be considered as complementary and more than one test should be used in order to cover the spectrum of relevant pressor drives. All tests were affected by substantial variability. Sufficiently large samples should be used in order to assure appropriate statistical power and precision when the effects of investigational drugs on these test responses are studied.