Figure 27

Pathophysiologic mechanisms related to hypertension in parenchymal renal disease: schematic view of candidate mechanisms. The balance between cardiac output and systemic vascular resistance determines blood pressure. Numerous studies suggest that cardiac output is normal or elevated, whereas overall extracellular fluid volume is expanded in most patients with chronic renal failure. Systemic vascular resistance is inappropriately elevated relative to cardiac output, reflecting a net shift in vascular control toward vasoconstricting mechanisms. Several mechanisms affecting vascular tone are disturbed in patients with chronic renal failure, including increased adrenergic tone and activation of the renin-angiotensin system, endothelin, and vasoac-tive prostaglandins. An additional feature in some disorders appears to depend on reduced vasodilation, such as in impaired production of nitric oxide.

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