Preface

T his spring issue of Hemodialysis International, Volume 7, No. 2, contains an editorial, five original articles, six review articles, a case report, and a hemodialysis quiz. In the editorial, Twardowski (page 109) describes fallacies of high-speed or short dialysis with a high ultrafiltration rate leading to intradialytic hypotension, positive sodium balance, volume-dependent interdialytic hypertension, left ventricular hypertrophy, and high cardiovascular mortality. The high blood flow required to maintain urea clearance in short dialysis contributes to inferior blood access results. Twardowski advocates longer ( 5 hr) dialysis sessions with lower blood flows in a thrice weekly schedule for patients without residual renal function and prone to intradialytic hypotension. Shorter dialysis sessions may be acceptable with increased dialysis frequency (every other day or daily) and for patients with substantial urine output. Ahmad (page 118) argues that the recent emphasis on patient outcomes (hospitalization and survival) as measures of adequacy of dialysis, while pertinent in defining adequate dose of dialysis in a group of patients, is not helpful in evaluating the impact of dialysis dose in individual patients. He evaluated a test called choice reaction time (CRT), which is the time in ms for patients to correctly identify the color of a randomly flashing panel. Patients in good general health respond quickly, so their CRT is short. In patients with end-stage renal disease, the shortest time was observed after successful transplant, and this was not different than in healthy individuals. In dialysis patients, a higher dose of dialysis had a beneficial influence on the CRT. The use of peripheral quantitative computed tomography (pQCT) in patients with severe secondary hyperthyroidism is presented by Brancaccio et al. (page 122). Their paper clearly shows that pQCT is an attractive technique in bone monitoring of hemodialysis patients, due to the low radiation exposure, the ability to assess volumetric density of cortical and trabecular sites separately, as well as to non-invasively evaluate the geometric and biomechanical properties of the bone. The results of locking failing hemodialysis catheters with tissue plasminogen activator (tPA) are reported by O’Mara et al. (page 130). tPA was administered 62 times in 25 patients with 30 catheters. Complete or partial restoration of patency was achieved in 43 episodes; partial restoration of patency was achieved in 20 episodes. Nineteen episodes failed to respond to tPA. These 19 episodes occurred in 13 catheters, 12 of which ultimately underwent radiologic evaluation; an extraluminal cause for low blood flow was found in all. The authors conclude that failure to respond to tPA strongly suggests an extraluminal cause of catheter malfunction. Despite the use of highly efficient antihypertensive drugs, blood pressure (BP) is poorly controlled in the vast majority of hemodialysis patients. Many of them show no reduction in nocturnal BP, a finding that is associated with left ventricular hypertrophy. Katzarski et al. (page 135) investigated the effect of removal of the fluid overload from extracellular volume on BP control in patients with ‘‘dialysis resistant’’ hypertension,. Even moderate prolongation of dialysis sessions from 253 15 min to 273 25 min together with strict control of sodium balance over 3–4 months, allowed control of blood pressure in 10 of 16 patients. Acute renal failure (ARF) after cardiac surgery is associated with significant morbidity and mortality. Thakar et al. (page 143) evaluated Chertow’s prognostic risk stratification algorithm (RSA) to predict the occurrence of postoperative ARF. A RSA derived from recursive partitioning was constructed and was validated on an independent sample of 24,660 patients who underwent cardiac surgery at the Cleveland Clinic Foundation between 1993 and 2000. Ing et al. (page 148) review treatment methods for severe hypophosphatemia in patients requiring hemodialysis. Although hyperphosphatemia is typical in renal failure, hypophosphatemia can develop in renal failure patients who are malnourished or aggressively dialyzed. Also, life threatening hypophosphatemia may develop in patients without renal failure who require prolonged, intensive hemodialysis for treatment of severe methanol or ethylene glycol intoxication. Hypophosphatemia is commonly prevented or treated with the oral or intravenous administration of soluble phosphate salts; however, there are situations where phosphorus-enriched dialysates may be preferable for the purpose of phosphorus administration. The authors describe various preparations of soluble phosphate salts and their use in hemodialysates. Vanholder et al. in two papers (pages 156 and 162) review uremic toxins and methods of their removal. About 100 uremic retention solutes have been identified at present, but not all of these compounds are necessarily toxic. A convenient way to classify uremic