Robert Zweiker
Hyper t o n i e u n d H ö h e Hypertension and moderate to high altitude S U M M A RY Exposure to moderate or high altitudes has a great impact on the human cardiovascular system. As a mechanism of acclimatization circulatory functions try to adapt to lower oxygen partial pressures, which are the consequence of lower barometric pressure at higher altitudes. The resulting hypoxemia stresses sympathetic tone and elevates blood pressure as well. Additionally, cardiac load and peripheral arterial pressure escalate as total body water decreases due to dehydratation while the hematocrit rises as erythropoesis is stimulated. Hypertensive patients should therefore have cardiac and pulmonary examinations before spending time at altitudes above 2500 meters. A bicycle ergometer test is ideal to check physical fitness and blood pressure behavior in advance. Uncontrolled hypertension is one of the major contraindications for high altitude exposures. On the other hand, exposure to moderate altitudes below 2500 m is not dangerous for hypertensives and might even improve a variety of cardiovascular and laboratory risk stratification parameters as well as possibly lowering blood pressure. It is very beneficial, if patients participate in exercise training programs at moderate altitude levels on a regular basis.When considering antihypertensive therapy strategies for patients planning to spend appreciable amounts of time at moderate altitudes dehydration and activation of the renin angiotensin aldosteron system should be kept in mind. In this setting, RAAsystem blockers might cause an undesirable drop in blood pressure. Keywords: hypertension, altitude, antihypertensive medication, bicycle stress test.
Z U S A M M E N FA S S U N G Ein Aufenthalt in mittleren Höhen und darüber bedeutet für das Herz- und Kreislaufsystem des Menschen eine gravierende Umstellung im Vergleich zu den Lebensbedingungen in einer Seehöhe < 2000 m. Durch Akklimatisationsvorgänge stellt sich der Kreislauf nach einigen Tagen auf den niedrigeren Luftdruck und den damit einhergehenden niedrigeren Sauerstoffpartialdruck in der Höhe ein, wobei diese Anpassungsvorgänge mit einem deutlich stimulierten Sympathiko-
55
