Dialysis hypotension: do we see light at the end of the tunnel?

Abstract

Symptomatic hypotension is a common problem in The more eYcient the refill in proportion to UF, the haemodialysis treatment. It seriously impairs the state more constant the IVV will be maintained. The main of well-being of the patients and it may induce severe factors that influence the refill are listed in Table 1. cardiac arrhythmias. Despite profound improvements When refill lags behind ultrafiltration, other com- of haemodialysis technique in recent years the fre- pensatory mechanisms are required to maintain blood quency of recurrent intradialytic hypotensive episodes pressure. In this context cardiac output, systemic vascu- has remained nearly unchanged (occurring in approxi- lar resistance (SVR) or both may increase to keep up mately 20-30% of all HD sessions (1)). Because of the perfusion pressure. There is a sequence of regulatory increasing age of today's dialysis patients and because mechanisms that increases arterial and venous vascular of the growing prevalence of diabetic end-stage kidney tone in response to IVV diminution (extensively disease, this problem is likely to become even more reviewed in (2)). These mechanisms are listed in important in the future. Table 2. Sympathetic activation increases heart rate From a clinical point of view one may consider two and contractility. However these eVects are not very groups of subjects susceptible to dialysis hypotension: eYcient in blood pressure defence, since their gain is (i) A larger group of basically normotensive or hyper- limited by venous return. The latter is usually reduced tensive patients who are prone to intradialytic in states of deficient vascular refill. decreases in systolic blood pressure of 30 mmHg Based on these physiological considerations four or more, resulting in symptomatic hypotension. pathophysiological conditions predisposing to intradia- Patients in this group are often diabetics or have lytic hypotension have been intensively investigated: advanced left ventricular hypertrophy causing dia- (i) insuYcient refill, (ii) autonomic dysfunction, (iii) stolic dysfunction. left ventricular diastolic dysfunction, and (iv) imbal- (ii) A smaller group of patients with sustained hypoten- ance of vasoactive agents. sion that also persists throughout the interdialytic interval. This group usually includes anephric patients and those that have been on haemodialysis Plasma refill for many years. The systolic blood pressure of these patients will rarely exceed 100 mmHg. A modest Plasma refill is important for cardiovascular stability reduction in blood pressure triggered by ultrafiltra- during haemodialysis treatment. Its extent determines tion will suYce to cause symptomatic hypotension. the gain of neurohumoral compensation. Typical pathophysiological conditions that impair the refill are This contribution is an attempt to develop diagnostic