Dialysis-related amyloidosis: Pathogenetic aspects and therapeutic considerations

Rationale and experience with short daily hemofiltration

Patients with end-stage renal disease (ESRD) have morbidity and mortality rates that are much higher than those found in the general population. The nonphysiologic nature of thrice-weekly hemodialysis may be partially responsible for the poor outcomes in this patient population. In response to the problems encountered with conventional hemodialysis schedules, a number of investigators have explored potential solutions to the problem. One such solution is to increase the time and/or frequency of hemodialysis. With this approach, ESRD patients have been observed to have better anemia management and blood pressure control, as well as improvements in quality of life. Hemodialysis is based on diffusion of solutes across a semipermeable membrane such that only small molecules are readily removed. Therefore a second solution has been to utilize hemofiltration instead of hemodialysis. Hemofiltration utilizes convective clearance of molecules, resulting in an improvement in the removal of larger solutes, much like the glomerular basement membrane of the kidney. Despite the accumulated evidence that thrice-weekly hemofiltration adds to the benefits seen with increasing hemodialysis time and/or frequency, the use of hemofiltration has been limited by the available technology, cost, and low access blood flows. However, current technological advances in equipment and access creation are addressing these problems. With these advances, a number of investigators have also explored the potential benefits of daily hemofiltration as a treatment option for ESRD. The preliminary results suggest that improvements in blood pressure, beta2-microglobulin (beta2M) levels, and quality of life are possible.

Hip arthroplasty in chronic dialysis patients

We retrospectively reviewed 15 patients (24 hips) on chronic renal dialysis who underwent hip arthroplasty between 1970 and 1990. The average age at surgery was 39 years; the average follow-up was 8 years (range, 1-19 years). All follow-up of less than 5 years relates to those patients who died. Of these 24 hips, 14 (58%) failed or were failing due to loosening; the average time to revision was 7 years (range, 1.5-14 years). A complicated course was experienced in 16 hips (66%), primarily related to medical difficulties. There was one perioperative death. The following orthopedic complications afflicted 5 hips (21%): one femur fracture during revision; one femur fracture at 2 months after revision; one dislocation during seizure; one displacement of acetabular cup requiring recementing; and late generalized septic death of one patient (with both hips involved). Within an average of 3 years (range, 15 months to 7 years) after their index surgery, 6 of the 15 patients (40%) died. The patients who lived were chronically ill, and all but three remained on long-term dialysis. The functional level of all those remaining on dialysis steadily declined, and none reached a quality of life comparable to an osteoarthritic patient. This study confirms a previously reported high mortality and morbidity rate in this population. Despite their difficulties, 22/24 primary hips were relieved of pain and increased in function; six patients returned to work. We see no better alternative for pain relief in total hip arthroplasty, particularly in view of contemporary surgical techniques and improved medical management.

Principles and practice of hemofiltration and hemodiafiltration

There is growing interest in the convective dialysis therapies, hemofiltration (HF) and hemodiafiltration (HDF). Both require dialysis membranes which are highly permeable to solutes as well as fluid, and in both cases large volumes of ultrafiltration are the condition for convective transport. In HDF the convection is combined with diffusion, and as a consequence, maximum clearance over the entire molecular weight spectrum is achieved. Optimal forms of HDF provide urea clearance 10-15% higher than the corresponding diffusive mode. The larger the solute, the greater is the impact of convection, and beta2-microglobulin (beta2m) levels may be up to 70% reduced. Traditional postdilution HF provides high clearance of medium sized and large molecules. Satisfactory clearance of small solutes requires blood flows in excess of 500 ml/min. With access to practically unlimited volumes of substitution solution through on-line ultrafiltration, predilution HF can now be used. This increases the clearance of small solutes to an acceptable range. For HDF as well as HF, large patient populations consistently treated for longer periods of time are needed to make valid outcome comparisons with other therapies.