On the face of it, most of us deliver “routine” hemodialysis (HD) for most of our patients and probably believe that we do so in much the same manner as everyone else. Nevertheless, there are considerable differences in patient outcomes around the world
The differences in HD delivery should be considered in 2 separate scenarios: A. “Conventional” HD, relating to typical center-based 3-times-weekly dialysis B. Less commonly used HD modalities of hemodiafiltration, short daily dialysis, and nocturnal (or quotidian) dialysis.
Conventional Dialysis For most patients in the developed world, this means 3-times-weekly dialysis, incorporating a long break (eg : Friday to Monday) or twice weekly. Hardware Consumables Amount of dialysis Dialysate composition Dialysis access Volume
Hardware Main difference: 1) concentrates for dialysate, including solid versus liquid concentrates and mixing ratios, as well as central versus individual dialysis fluid mixing systems; (2) mechanism of ultrafiltration control; and (3) add-ons, such as blood volume monitors and sodium profiling.
Consumables Differences in dialysis tubing and needles appear to have little impact on outcomes, especially because now virtually all are sterilized using either steam or ethylene oxide Of greater controversy is the influence of dialysis membranes on outcomes.
Membrane Permeability Outcome High-flux dialysis showed a significant survival benefit of 37%, after adjustment, of patients with a low serum albumin (<4g/d) and diabetes mellitus. Serum albumin>4g/dL=> no survival benefit.
HEMO study Low flux: B2Mclearance <10ml/min(3) High flux: B2M clearance >14ml/hr/mmHg, with mean B2M >20ml/min(34)
N Engl J Med, Vol. 347, No. 25 · December 19, 2002
No significant survival difference Patients who were enrolled in the study after >3.7 yr of maintenance dialysis: benefit on CVA and overall mortality.
Studies such as the DOPPS have shown that high- flux dialyzer use varies considerably throughout DOPPS countries,18 with cost offered as a major reason. One attempt to minimize this is the practice of reuse. Reuse of dialyzers saves money, but A. potentially exposes the patient to infection if the sterilization process is inadequate. B. Exposure to residual cleansing agents C. Lose efficiency over multiple use. banned by health authorities in many countries
Amount of Dialysis NCDS: Kt/V Recommend a minimum achieved Kt/V of 1.2- 1.4, although this target has not truly been put to a test compared with a lower target. 0.8: Safe; 1.0 : a target of safety margin HEMO: failed to show benefit of 1.6 over 1.2.
Blood Flow Blood flow: Asia and Japan: 200ml/min US: 400 ml/min is common. Little to suggest high blood flow is problematic. High blood flow and cardiovascular instablility don’t appear to have materialized. => High blood flow(300-350 ml/min) and high dialysate flow(700ml/min) should be matched for maximum efficacy.
Analysis of these databases suggests that dialysis sessions less than 4 hours in otherwise conventional dialysis are associated with increased mortality. HEMO: (only RCT) major technique for increasing Kt/V in that study was by increasing time Concerns around shorter duration: Underdialysis in terms of urea removal. Poorer removal of time-dependent molecules. Poorer Volume control.
Dialysate Composition K: Dialysate potassium concentrations tend to vary from 1.0- 3.0 mmol/L, but there are no hard-outcome RCT data to back this up. If arrhythmia(observational study) >3.0=>better solute removal. Bicarbonate: Alkalosis is less tolerated. Immediately postdialysis, serum bicarbonate levels may come close to approximating the dialysate bicarbonate concentration, although this quickly decreases during the following 30-40 minutes. Predialysis HCO3 level: 21-22mEq/L: better survival (DOPPS)
Dialysate Composition Sodium: no hard-end-point data Calcium: Recent trends have suggested that lower serum calcium levels are beneficial for dialysis patients in terms of mortality High Ca: as parathyroid suppression previously. DOPPS: Ca>3.0 => worse outcomes.
Dialysis Access AVF: Japan and Italy:90% US: 50% AVG: Higher mortality and morbidity(stenosis, thrombosis) Catheter: infection. 20% new-start dialysis patients. Late referral. Successful fistula was improved by 34% if the surgeon previously had created at least 25 fistulas in his or her training period.
Catheter lock: Heparin lock: promote biofilm generation. 2 alternative locks: A. antibiotics B. Calcium citrate 225 patients with tunneled catheters randomly assigned to heparin or heparin plus recombinant tissue plasminogen activator once weekly : less malfunction in later. (HR H vs H+P: 1.91; 95% CI, 1.13-3.22 )
Volume Control and Blood Pressure Cultural difference(High salt diet in Asia) There is some evidence that larger interdialytic weight gains portend better prognosis on the basis that this represents better nutritional intake negative cardiovascular effects Blood volume monitoring => better for fluid removal.
Volume Control and Blood Pressure Use of antihypertensive agents in dialysis patients varies widely and different philosophies exist. HTN=> volume related(?) Blood pressures in the range of 140-160 mm Hg systolic (predialysis) are associated with the best outcomes. Antihypertensive agent: may promote intradialytic hypotension and chronically fluid overload.
Location of Dialysis hospitals or specialized satellite units. Australia and NZ: Home dialysis(11%in Australia) Outcomes for home HD patients frequently are reported as better than for satellite patients greater flexibility around scheduling and duration of sessions, empowers patients, and allows them to wrest back
ALTERNATIVE DIALYSIS HDF Mainly in Europe. This often is reflected in removal rates for B2M and is said to translate into decreased B2M amyloidosis and improved cardiovascular stability. Underpowered for mortality in 2 RCT.
Short daily Dialysis This modality uses 5-6 HD sessions weekly for 1.5-3 hours per session. FHN (Frequent Hemodialysis Network) RCT, which compared conventional HD with in-center short daily dialysis in North America, reported a positive outcome for the composites of survival and left ventricular hypertrophy and survival and quality of life. Too small to show survival benefit. more frequent needling of an arteriovenous access AVF failure
Nocturnal dialysis NZ, France: 3-times-weekly nocturnal dialysis using 8-hour dialysis sessions Toronto: 5-6 times weekly In Australia, ~45% of all home HD is now nocturnal HD, predominantly as the 3.5-times- weekly model. Canada short-term RCT: LVH improvement in MRI vs conventional HD FHN RCT: failure to demonstrate benefit.
Japan has long had better dialysis mortality figures than any other country without a clear explanation, except for a low background general population mortality rate and a very low transplant rate. the United States has had among the worst dialysis mortality rates. The reason has been attributed to an older dialysis population, more patients with diabetes, and and more patients with comorbid conditions
Other HD-specific factors in the United States may include the tendency to shorter dialysis sessions, higher use of catheters, and lower use of AVFs.