Clinical Dilemmas in Dialysis: Managing the Hypotensive PatientPathophysiology of dialysis hypotension: An update☆,☆☆
Section snippets
Incidence and effect on outcomes
Dialysis hypotension occurs in up to 20% of dialysis sessions. Whereas it seems that frequent intradialytic hypotension would lead to increased morbidity and mortality, this has not been well documented. A low predialysis blood pressure (BP) is a marker of increased mortality,1 but this may be due to the fact that low predialysis BP is a marker of pre-existing cardiac disease in the end-stage renal disease (ESRD) population. Similarly, patients with frequent hypotensive episodes during dialysis
Basic concepts
The pathophysiology of dialysis hypotension was reviewed in 1991.6 The basic concepts have not changed, and the reader is referred to that publication for detailed references. Several important points can be re-emphasized. The blood volume in a typical dialysis patient is approximately 4.5 L, with a corresponding plasma volume of approximately 3 L.7 In patients undergoing thrice-weekly dialysis schedules and gaining 1.5 kg/d, the therapeutic requirement is to remove 3 L of fluid per dialysis
Cardiac compensatory mechanisms
Changes in cardiac rate in response to hypovolemia are often impaired in dialysis patients. Whereas cardiac rate changes may be important in increasing cardiac output from baseline (eg, during physical activity), they appear to be less important in maintaining cardiac output under conditions of decreased filling. For example, studies in dogs receiving propranolol during hemorrhage indicate that this cardiac rate change is of minimal importance in maintaining cardiac output during hypovolemia.8
Plasma refilling
The primacy of plasma refilling is indicated by the fact that, if one does not remove fluid during dialysis, intradialytic hypotension is rare, indeed. This clarifies the fact that the ultimate cause of hypotension is reduced cardiac filling. The initial compensatory mechanism is refilling of the plasma water space from surrounding tissue spaces. As a result of refilling, even though 1 entire plasma volume is removed during dialysis, the blood volume typically decreases only by 5% to 20%.11
The
Venous capacity: Interaction with arterial tone
Detailed hemodynamic analysis of IHEs suggests 2 important things. (1) There is no sudden decrease in plasma volume just before a hypotensive episode. (2) IHEs seem to be due to a decrease in cardiac output engendered by reduced cardiac filling.23, 24 How can this be explained?
Most of the 3 L or so of plasma volume resides in the veins, and several organ perfusion systems, notably skin and splanchnic, contain veins that can markedly alter their capacity.25 A slight loss in venous tone in either
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Cited by (285)
Why is Intradialytic Hypotension the Commonest Complication of Outpatient Dialysis Treatments?
2023, Kidney International ReportsInterventions to reduce falls among dialysis patients: a systematic review
2023, BMC NephrologyAcute kidney injury in neurocritical care
2023, Critical Care
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Address reprint requests to John T. Daugirdas, MD, Professor of Medicine, University of Illinois at Chicago, VA Chicago Hospital—West Side, 820 South Damen Ave, Chicago, IL 60612. E-mail: [email protected]
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