Vasodilator drugs reduce peripheral vascular resistance but lead to a secondary baroreflex-mediated chronotropic effect. After angiotensin-converting enzyme inhibition, blood pressure falls without associated tachycardia. In a previous study it was observed that enalapril increased vagal tone in essential hypertensive patients. In order to evaluate the effect of enalapril on sympathetic stimulation 10 mild to moderate hypertensive patients were studied during static (hand grip) and dynamic exercise (bicycle ergometer), after 2 weeks of placebo and after 1 month of treatment with 20-40 mg enalapril once daily. Enalapril significantly reduced blood pressure and the rate-pressure product at rest and at peak dynamic exercise. There was no effect on supine and maximal heart rate. Enalapril also significantly reduced blood pressure during hand grip, but did not interfere with the rate of the increase. Thus, enalapril does not seem to interfere with sympathetic adaptation to stress.

Adult↗

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Acid-base changes in acute exacerbation of chronic hypercapnia in man.

Acid-base parameters were studied in 10 adult patients with chronic respiratory failure during spontaneous acute exacerbations of chronic hypercapnia and after return and stabilization of PaCO2 values at previous levels with improvement of clinical conditions. All factors interfering with acid-base equilibrium were carefully avoided. The results of this investigation confirm qualitatively those obtained by GOLDSTEIN et al. [7] in dog studies and those of INGRAM et al. [9]in human studies: increasing degrees of chronic hypercapnia tend to minimize the pH reduction induced by acute PACO2 changes. From a quantitative standpoint INGRAM's data in humans are considerably different from GOLDSTEIN's data obtained in dogs. Our data, although numerically limited, confirm the acute deltaH+/deltaPaCO2 slope obtained from dogs by GOLDSTEIN et al. As data are not yet sufficient, definitive conclusions cannot be drawn. However the pattern of acid-base equilibrium changes in man in this situation seems to be similar to that observed by GOLDSTEIN et al. in the dog and could be described with reasonable accuracy by the theoretical model of LEUENBERGER et al.[13].

Acid-Base Equilibrium↗

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