[Hypotensive periods during hemodialysis]

Hypotensive periods occur frequently during a haemodialysis session. The pathogenesis of intradialytic hypotension is multifactorial. The initiating factor is a decline in blood volume. Important contributory factors are inadequate vascular reactivity during haemodialysis and structural cardiovascular abnormalities. Compared with 'standard' haemodialysis, vascular reactivity is clearly increased during isolated ultrafiltration, haemodialysis with lowered fluid temperature (e.g. 36 degrees C), and haemofiltration. The single most important factor explaining these differences in vascular response is the thermal energy balance during the various treatment modalities. With a critical reduction of cardiac filling, the Bezold-Jarish reflex may occur, leading to paradoxical vasodilation and bradycardia.