John A. Sargent

Iron requirements in hemodialysis.

The correction of anemia in dialysis patients with erythropoietin (EPO) can be frustrated by insufficient iron. To address this effect, we preloaded candidate EPO patients with intravenous iron in the early 1990s. Preloading with 900–1,525 mg of iron yielded the following results: 70% of patients had increasing hematocrits (HCTs) without EPO, and 40% of patients had HCTs greater than 30%. Apparent lack of iron led to blood loss studies. Routes evaluated were blood sampling, dialyzer clotting, blood in the dialyzer circuit and postdialysis bleeding. Projected annual losses were between 2,516 and 5,126 ml, depending on circuit and posttreatment losses. In terms of red cell loss, the results are comparable to those in the early days of dialysis before the introduction of current technology. Extension of these studies to daily dialysis predicts possible losses with this 6 times a week therapy of between 4,663 and 9,884 ml per year.

Hemofiltration: An Unnecessarily Complex Method to Achieve Hypotonic Sodium Removal and Controlled Ultrafiltration

High flux hemofiltration (HF) has been routinely reported to result in decreased morbidity compared to hemodialysis (HD). Examination of Na and water transport in these comparative studies indicates:

Theoretical considerations on molecular transport in dialysis and sorbent therapy for uremia.

The technology of uremic blood purification has grown rapidly over the past decade and has provided the clinician with a wide range of therapeutic options. These options involve mass transfer processes which may be primarily due to diffusion or convection, or a combination of both mechanisms. However, regardless of the mechanism of molecular transport, evaluation of the clinical utility of these therapies requires studies which provide sufficient data to solve the appropriate rate equations and to close mass balances. Data from the recent hemodialysis, peritoneal dialysis and sorbent literature are analyzed to show the magnitude of variability in both patient and therapy-related mass balance paramters for urea nitrogen (U) and middle molecules (MM) and to provide unambiguous comparisons for some of these therapies. A theoretical model is developed to describe sorbent-mediated gut elimination of solute as a first-order clearance limited by sorbent saturation. The model is used to analyze data in the literature on AL (OH)3 facilitated gut clearance of phosphate and indicates a gut P clearance of approximately 20 ml/min with maximum removal of approximately 800 mg P/24 hrs. Similar analysis of oxystarch indicated a gut U clearance of 2.5 ml/min and maximum removal of 1.5 gm/24 hrs.

Identifying the Value of Computers in Dialysis

Dialysis providers use computers to automate complicated tasks, ease staff burden, and develop knowledge or understanding to improve operations and patient care. Some applications are successful, others are not. Success can be economically quantified. Business – billing and accounts receivable computerization – can yield over USD 5.00 for USD 1.00 invested. The clinical case is more complex and difficult to economically justify. Computerization of clinical information for charge capture is the simplest application (< USD 1.00/treatment) yielding the greatest benefit. Economic benefits for improving quality of care through electronic medical records are more problematic. Provider benefit of clinical computing is strictly the net income from more dialysis treatments. Greater complexity – e.g., total electronic records – means more expensive systems and increased staff effort. Many systems cost in the USD 5.00 + range which must be paid by increasing provider overhead. Dialysis providers must determine the point where computerization no longer decreases operational costs as computing cost increases. This is a classical optimization problem; its solution is crucial to the economic health of the dialysis enterprise.