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Haemodialysis 

Haemodialysis

Chapter:
Haemodialysis
Author(s):

Ken Farrington

and Roger Greenwood

DOI:
10.1093/med/9780199204854.003.210701_update_001

Update:

Timing of initiation of dialysis—the IDEAL (Initiating Dialysis Early And Late) study revealed that planned early initiation was not associated with an improvement in survival or clinical outcomes.

Frequency of dialysis—the randomized Frequent Hemodialysis Network Trial showed the benefits of 6 times weekly versus conventional 3 times weekly sessions.

Management of heparin-induced thrombocytopenia—recommendations for the use of heparinoid or argatroban.

Management of hypertension in dialysis patients—discussion of the general move for guidelines to become less prescriptive, recognizing risks of overtreatment as well as of undertreatment.

Management of hyperlipidaemia in dialysis patients—discussion of the findings of the SHARP trial, which showed that lowering LDL cholesterol with simvastatin plus ezetimibe reduced major atherosclerotic events, but did not have significant effects on cardiovascular or total mortality.

Updated on 25 May 2011. The previous version of this content can be found here.
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date: 30 March 2017

Over the past four decades, maintenance haemodialysis has proved to be a highly successful treatment for patients with endstage renal disease. In the developed world, the haemodialysis population continues to increase and is becoming more elderly and dependent. However, despite considerable advances in haemodialysis technology and other significant improvements, such as those in renal anaemia management, the long-term clinical outcomes for patients remain much less good than those of other people with comparable characteristics but without renal failure.

Dialysis adequacy—working definitions are based on small-solute—typically urea—removal, which occurs mainly by diffusion. Current guidelines recommend targeting a normalized urea clearance (eKt/V) in excess of 1.2 per session for thrice-weekly treatment. Higher doses of dialysis delivered thrice weekly do not produce significant improvement in outcomes, but there is evidence that frequent treatment (6 times weekly) can do so, and there is also a need to incorporate more holistic approaches into the concept of adequacy.

Technical aspects of haemodialysis—high-flux membranes are needed to achieve significant removal of middle molecules, of which β‎2-microglobulin is the prime example. Use of such membranes can slow the progression of dialysis-related amyloidosis, a complication of long-term haemodialysis related to β‎2-microglobulin retention, but firm evidence of an effect on survival is lacking. The technique of haemodiafiltration adds a significant convective component to high-flux haemodialysis, providing improved β‎2-microglobulin clearance, with observational studies suggesting a survival benefit.

Vascular access—the need to secure and maintain reliable vascular access is fundamental to achieving adequate dialysis and maintaining health. An arteriovenous fistula is the preferred option, with fewer complications and longer survival than other access options. The current overdependence on tunnelled lines contributes to morbidity and excess mortality, mainly from line-related sepsis, and represents a failure in access provision.

Complications of haemodialysis—the main acute complication of haemodialysis is intradialytic hypotension, resulting from an imbalance between the ultrafiltration rate and the rate of vascular refill. Underlying cardiovascular disease, antihypertensive drugs, autonomic dysfunction, shortened dialysis times, large interdialytic fluid gains, and inaccurate dry-weight assessment all predispose. Postdialysis headache is relatively common, as is prolonged bleeding from the fistula after needle removal. Dialyser reactions are less common. More serious bleeding problems with anticoagulation are rare. True heparin-induced thrombocytopenia (HIT-II) is very rare, but is potentially life threatening.

Comorbidities in patients on dialysis—the high mortality in the dialysis population is mainly due to accelerated cardiovascular disease. Traditional risk factors for atheroma such as hypertension and dyslipidaemia are common, but difficult to interpret: there seems to be a paradoxical relationship between blood pressure and mortality in patients on haemodialysis (‘reverse epidemiology’), and there are questions about the appropriateness of blood pressure targets in the absence of randomized interventional trials of the effect of blood pressure reduction in this population. Similarly, while therapy to lower LDL cholesterol may reduce the incidence of major atherosclerotic events in dialysis patients, it does not produce a significant reduction in cardiovascular or overall mortality. In addition, there are a myriad of less traditional risk factors operating in dialysis patients, including anaemia, disturbances of calcium and phosphate metabolism, hyperhomocysteinaemia, increased oxidative stress, and elevated inflammatory markers. It may be that the combined effect of all these risk factors outweighs the benefits of a single intervention, and more global approaches are required. It remains to be seen whether the improved control of the uraemic milieu possible with more frequent dialysis schedules will impact on survival.

Is haemodialysis in the best interest of the patient?—haemodialysis, although universally applicable, has its limitations. Dialysis initiation may not improve quality of life or survival for some very high-risk dependent patients, for whom supportive therapy, and not dialysis, may be the best treatment option.

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