The patient with resistant hypertension. Cations, volume, and renal factors.

Hypertension that is truly resistant to modern antihypertensive therapy is uncommon. In the majority of cases, apparent resistance is more likely associated with poor patient adherence, interacting drugs, drug interactions, and inappropriate drug dosages. Sodium and fluid volume play a major role in resistant hypertension. There is considerable evidence to support the role of dietary sodium restriction in successful nonpharmacological treatment of hypertension. Salt sensitivity in humans appears to represent at least one factor determining individual susceptibility to variable salt intakes. Sodium and water retention may lead to refractoriness to many antihypertensive agents, and there is evidence to suggest that extracellular fluid volume expansion also plays a role in many hypertensive patients. While retention of sodium and water is well established early in patients with renal parenchymal disease, hypertension associated with progression of renal parenchymal disease is complicated by other factors that include interactions between hemodynamic and humoral factors, functional changes in adrenergic responses, and structural vascular disease. The role of other cations such as potassium, calcium, and magnesium in resistant hypertension has yet to be established.