Using a double-blind, randomized, cross-over protocol, we studied the effect of a single dose of oral caffeine on plasma renin activity, catecholamines and cardiovascular control in nine healthy, young, non-coffee drinkers maintained in sodium balance throughout the study period. Caffeine (250 mg) or placebo was administered in a methylxanthine-free beverage to overnight-fasted supine subjects who had had no coffee, tea or cola in the previous three weeks. Caffeine increased plasma renin activity by 57 per cent, plasma norepinephrine by 75 per cent and plasma epinephrine by 207 per cent. Urinary normetanephrine and metanephrine were increased 52 per cent and 100 per cent respectively. Mean blood pressure rose 14/10 mm Hg one hour after caffeine ingestion. There was a slight fall and then a rise in heart rate. Plasma caffeine levels were usually maximal one hour after ingestion but there was considerable individual variation. A 20 per cent increase in respiratory rate correlated well with plasma caffeine levels. Under the conditions of study caffeine was a potent stimulator of plasma renin activity and adrenomedullary secretion. Whether habitual ingestion has similar effects remains to be determined.

https://www.nejm.org/doi/pdf/10.1056/NEJM197801262980403?listPDF=true

Effects of caffeine on plasma renin activity, catecholamines and blood pressure.

In the first of two papers, the details and results of a systematic, carefully standardized application of dye dilution technic to the measurement of cardiac output are reported. A substantially reduced output was a consistent finding in older subjects. Factors responsible for this are analyzed in this article, and further interpretations are made in the succeeding article. One result of the analysis of time-concentration curves of dye provides an interesting relationship to clinical estimates of circulation time.

Changes in Cardiac Output with Age

The absence of conspicuous increments of venous pressure after severe damage to the right ventricle of the dog, with a discussion of the relation between clinical congestive failure and heart disease

https://www.amjmed.com/article/0002-9343(48)90158-2/pdf

The hemodynamic response of man to nor-epinephrine and epinephrine and its relation to the problem of hypertension

Die Dynamik des arteriellen systems

/pdf/a-clinical-study-of-the-action-of-10-commonly-used-drugs-on-13p9xqscnj.pdf

A clinical study of the action of 10 commonly used drugs on cardiac output, work and size; on respiration, on metabolic rate and on the electrocardiogram

/pdf/studies-of-the-heart-and-circulation-in-disease-estimations-4lvha8wi21.pdf

Studies of the heart and circulation in disease; estimations of basal cardiac output, metabolism, heart size, and blood pressure in 235 subjects

A method for the determination of minute amounts of ethyl iodide in air, water, and blood by means of its reaction with silver nitrate; and experiments bearing on the determination of blood flow by means of ethyl iodide

Clarence James Gamble

Papers

A clinical study of the action of 10 commonly used drugs on cardiac output, work and size; on respiration, on metabolic rate and on the electrocardiogram

Studies of the heart and circulation in disease; estimations of basal cardiac output, metabolism, heart size, and blood pressure in 235 subjects

A method for the determination of minute amounts of ethyl iodide in air, water, and blood by means of its reaction with silver nitrate; and experiments bearing on the determination of blood flow by means of ethyl iodide

The solubility of ethyl iodide in human blood and its correlation with the erythrocyte count