[Arterial hypertension in patients on chronic hemodialysis]

Arterial hypertension is frequent among chronically dialyzed patients. The kidney obviously plays a major role in arterial blood pressure control. There is a large number of experimental data emphasizing different factors (in addition to renin important in renal hypertension prognosis) such as: sodium balance, angiotensin, etc [1-8]. Sympathetic activity disorders or lack of vasodilatory prostaglandins and quinine may also play a certain role. In uremic patients peripheral arteriolar resistance is increased, unlike normotensive uremic patients or those who prove to be normotensive upon clinical examinations [8, 11-15]. Hypertension occurs in approximately 80% of patients with chronic renal failure, producing a number of complications primarily affecting the CNS and systemic circulation [5-8, 10, 11, 13]. The study concerned patients on chronic dialysis, with a male to female ratio of 69.9%:32.1%. In most of them the underlying disease, which caused chronic renal failure, was glomerulonephritis (60.0%), then pyelonephritis (17.0%) and nephrosclerosis, nephrolithiasis, polycystic kidney and, finally, renal tumours. The effect of permanent haemodialysis during the first year of treatment, was efficacious on hypertension in 1704 (65.1%) patients; in 672 (25.7%) patients therapeutical effects were achieved by dialysis and antihypertensive drugs, while in 240 (9.2%) subjects there was no improvement. General observations suggest that two types of arterial hypertension persisted in patients with chronic renal failure: volume-dependent arterial hypertension which is more frequent (90-95%) among haemodialyzed patients and renin-dependent hypertension. Such findings are of utmost importance indicating that hypervolaemia is one of the major factors in the development of arterial hypertension in patients with chronic renal failure, with renin playing the secondary role. Salt-free diet should be used in the treatment of arterial hypertension for years, a well conducted haemodialysis is highly effective in the control of arterial hypertension among these patients. In our series of patients dialysed three times a week; normalization of blood pressure was faster with lower incidence of hypertensive crises during haemodialysis and with few complications. Water and sodium excess was reduced by frequent haemodialyses and sudden changes in electrolyte, hydrostatic and other metabolic effects were minimized. Increased values of plasma renin activity were observed in a small number of patients. Ultrafiltration is insufficient for normalization of blood pressure. Hypertensive crises were frequent in these patients. Their response to medicaments such as methyldopa, beta-adrenergic blockers or other antihypertensive drugs, was good. Severe changes in blood vessels, especially in fundus oculi blood vessels were frequent in these patients. The life of hypertensive glomerulonephritis patients was especially endangered (graphs 1-6). In addition to the mentioned factors arterial hypertension during haemodialysis may also be of cardiac origin, including increase in cardiac output due to arteriovenous anastomosis, disequilibrium syndrome, changes in osmotic gradient of both extra- and intracellular spaces with resultant arteriolar wall oedema, erythrocyte amount, hypoxia, composition of dialysis fluid (sodium concentration), plasma osmotic pressure, metabolic acidosis and other factors. More recently, natriuretic hormone has also been indentified as a cause of vascular refraction. Peripherial arteriolar resistance as a cause of arterial hypertension among uremic patients must not be forgotten, because the genesis of arterial hypertension in patients with chronic renal failure is multifactorial. The highest percentage refers to volume-dependent arterial hypertension, whereas the percentage of other aetiologic factors is lower. Haemodialysis enables the normalization of blood pressure in most of hypertensive patients.