Plasma volume in resistant hypertension: guide to pathophysiology and therapy

It might be expected that the tremendous increase in available antihypertensives would eliminate resistant hypertension by allowing many alternatives to its treatment. In spite of this, resistant hypertension remains a common problem due, the authors feel, to a poor understanding of the pathophysiology of this condition, particularly an understanding of whether plasma volume expansion mediates resistance to antihypertensive therapy. The authors evaluated the status of plasma volume as a major determinant of response to therapy in nine patients with resistant hypertension. Measuring plasma volume using I125 radiolabeled albumin, they found eight patients with elevated plasma volumes and one patient with a contracted plasma volume at the time of presentation with resistant hypertension. In all eight patients with plasma volume expansion, aggressive diuretic therapy allowed goal blood pressure to be achieved. The patient with plasma volume contraction achieved goal blood pressure with vasodilator therapy. Plasma volume expansion is common in resistant hypertension and it mediates resistance to therapy. Measurement of plasma volume gives the clinician important insight into the pathophysiology of resistant hypertension and increases the likelihood of successful management of the resistant hypertensive patient.