Caffeine and Pressure Flow Autoregulation

Abstract

The benefits or detriments of caffeine on the human cardiovascular system have not been thoroughly studied and are still poorly understood. In a world where caffeinated beverages are evidently the adult drug of choice (e.g. coffee, energy drinks, soda, tea), investigating its effects on our bodies is of great importance. In this study, we examined the effects of caffeine, taken as a tablet, on pressure-flow autoregulation. Young adults between 18 and 21 years of age were the experimental subjects. They were instrumented to monitor systemic arterial blood pressure, peripheral blood flow, calculated peripheral vascular resistance, and the electrocardiogram during an autoregulatory maneuver in the absence and presence of caffeine. Caffeine-mediated vasoconstriction was observed as early as 15 minutes after its consumption. Sixty minutes post-caffeine, vasoconstriction was so prominent that autoregulation was abolished. This was reflected, in part, as a significant reduction in blood flow that accompanied a 3-fold increase in calculated peripheral resistance and a significant increase in systemic arterial pressure. Heart rate was unaffected by caffeine under our experimental conditions. We conclude that caffeine has the ability to inhibit significant cardiovascular properties including pressure-flow autoregulation. Even though more work is needed, the significant caffeine-mediated changes in flow, pressure and resistance during autoregulation could have serious consequences for the cardiovascular system specifically, and for one's overall health in general.

Caffeine and Reactive Hyperemia

“…These results are consistent with earlier experimental investigations from which we have reported significant caffeine-mediated peripheral vasoconstrictor effects in humans. In two of the three studies ( [14], current report) we have observed caffeine-mediated blockade of local blood flow-regulating mechanisms, i.e. pressure-flow autoregulation [14] and reactive hyperemia (current report).…”

“…In two of the three studies ( [14], current report) we have observed caffeine-mediated blockade of local blood flow-regulating mechanisms, i.e. pressure-flow autoregulation [14] and reactive hyperemia (current report).…”

“…In our previous experiments we have found that 200 -400 mg of caffeine disturbs the isoelectric line in standard limb lead ECGs and causes statistically significant elevations in peripheral vascular resistance that are accompanied by marked and significant reductions in blood flow and increments in systemic arterial blood pressure. These same doses of caffeine also significantly block peripheral vascular pressure-flow autoregulation [13] [14]. As yet we have not examined the detailed effects of caffeine on the intervals, segments and waves of standard limb lead ECGs.…”

“…The experiment was designed a priori and is a follow up to related experiments conducted in our laboratory [13] [14]. Initial variability was identified using Analysis of Variance for Repeated Measures (one-way ANOVA).…”

“…Before the vascular effects of nitric oxide (NO) were discovered [endothelial-derived relaxing factor, EDRF, Furchgott et al [13] [14], adenosine's ubiquitous role in regulating blood flow to the coronary and other vascular beds [15]- [28] was firmly established (see 15,19,28 for Reviews). With the intense interest in NO of the past few decades, most investigators either didn't know this about adenosine or have chosen to ignore it.…”