Caffeine and Reactive Hyperemia

The physiological/pathophysiological effects of caffeine on the human cardiovascular system have not been investigated by physiologists and are poorly understood. In a world where caffeinated beverages are evidently the adult’s drug of choice (coffee, energy drinks, soda, tea) investigating their effects on the physiology of the cardiovascular system is of considerable importance. In this experiment,?we investigated caffeine, taken orally as a tablet, on reactive hyperemia, a form of local control of blood flow. Young adults between the ages of 18 and 21 years were the experimental subjects. They were instrumented to monitor systemic arterial blood pressure, peripheral blood flow, calculated peripheral vascular resistance, heart rate and an electrocardiogram during a reactive hyperemia maneuver in the absence and presence of caffeine. Caffeine-mediated peripheral vasoconstriction was observed as early as 15 minutes after its consumption. Forty-five minutes later (60 min after consumption of caffeine) peripheral vasoconstriction was so prominent that reactive hyperemia was abolished. This was reflected, in part, as a marked and significant reduction in post-ischemia reactive hyperemia that accompanied a 2.5-fold increase in peripheral vascular resistance (P?0.05). Heart rate was unaffected by caffeine under our experimental conditions. We conclude that caffeine has the ability to inhibit important cardiovascular properties, including reactive hyperemia. If the effects that were seen in a digit are indicative of what caffeine might do in the heart and/or brain, then one has to question the wisdom of regularly consuming caffeine. More experimental physiological and pharmacological investigation is needed.

Caffeine and Pressure Flow Autoregulation

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.