Chronic hypotension in the dialysis patient.

Chronic hypotension, defined by a systolic blood pressure < 100 mmHg in the interdialytic period, affects 5-10% of hemodialysis patients, and is more prevalent among patients on long-term hemodialysis. This complication requires a substantial amount of medical and nursing care before and during dialysis to control its symptoms. Chronic hypotension is characterized hemodinamically by preserved cardiac index, heart rate or stroke volume, but reduced total peripheral vascular resistances. Although its pathophysiology is not well defined, a reduced cardiovascular response to vasopressor agents (such as norepinephrine and angiotensin II), associated with a down-regulation of their receptors, as well as an increased production of vasodilators (such as nitric oxide or adrenomedullin) are possibly involved. The treatment of this complication is not well defined and the measures recommended (contention in the lower limbs or the sympathomimetic agent midodrine) are of limited benefit.