Intradialytic Hypotension: Mechanisms and Outcome

Abstract

Intradialytic hypotension (IDH) occurs in approximately 10-12% of treatments. Whereas several definitions for IDH are available, a nadir systolic blood pressure carries the strongest relation with outcome. Whereas the relation between IDH may partly be based on patient characteristics, it is likely that also impaired organ perfusion leading to permanent damage, plays a role in this relationship. The pathogenesis of IDH is multifactorial and is based on a combination of a decline in blood volume (BV) and impaired vascular resistance at a background of a reduced cardiovascular reserve. Measurements of absolute BV based on an on-line dilution method appear more promising than relative BV measurements in the prediction of IDH. Also, feedback treatments in which ultrafiltration rate is automatically adjusted based on changes in relative BV have not yet resulted in improvement. Frequent assessment of dry weight, attempting to reduce interdialytic weight gain and prescribing more frequent or longer dialysis treatments may aid in preventing IDH. The impaired vascular response can be improved using isothermic or cool dialysis treatment which has also been associated with a reduction in end organ damage, although their effect on mortality has not yet been assessed. For the future, identification of vulnerable patients based on artificial intelligence and on-line assessment of markers of organ perfusion may aid in individualizing treatment prescription, which will always remain dependent on the clinical context of the patient.

Keywords: Dialysis; Hemodialysis; Intradialytic hypotension; Pathophysiology.

Fig. 1

Mechanisms behind intradialytic hypotension and its relation to outcome. BV, blood volume; IHD, intradialytic hypotension.

Fig. 2

Forearm vascular resistance and venous tone during isolated UF and hemodialysis. UF-only = isolated UF. UF rate was equal between UF-only and UF = HD. Dialysate temperature was 37.5°C. Measurements were performed by strain gauge plethysmography. From [32], with permission. FVR, forearm vascular resistance; UF, ultrafiltration.

Fig. 3

Representation of the concepts of stressed and unstressed BV. Pmsf is mean systemic filling pressure. The unstressed volume is the volume which fills the vasculature without a change in transmural pressure. The stressed volume is the volume that leads to an increase in transmural pressure. From [75], with permission.

Fig. 4

a, b De Jager-Kroch phenomenon. During a reduction in arterial inflow, pressure in the venous bed is reduced and due to passive recoil of the venous wall, BV is mobilized. From [80], with permission.