Chronic acid-base perturbations in hemodialysis patients treated with sevelamer hydrochloride: a two-year follow-up study.

Sevelamer hydrochloride (HCl) contains multiple amines that may cause a significant dietary acid load. To evaluate the impact of sevelamer on arterial blood gases, we followed two groups of stable hemodialysis patients for 24 months. The Sevelamer Group (n = 7) did not achieve the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (K/DOQI) goals for phosporus and Ca x P product and was switched from a calcium-based to sevelamer-based regimen. The Calcium Group (n = 7) achieved those goals and remained on calcium salts. Following sevelamer administration, a deterioration of chronic metabolic acidosis was revealed, which lasted throughout the study. Sevelamer therapy was associated with reduced cholesterol levels, improved serum phosphate, and Ca x P product, which facilitated the management of secondary hyperparathyroidism. No significant changes in acid-base status or other parameter tested were found in the Control Group. In conclusion, sevelamer intake caused small but persistent acid-base disturbances, which did not neutralize sevelamer's beneficial effects on mineral and lipid metabolism.

Causes of impaired delivery of hemodialysis prescription.

Urea kinetic modeling (Kt/V) is used to assess adequacy of hemodialysis (HD). However, serial Kt/V measurements may vary with time in the same patient, making the interpretation of the results difficult. The aim of the present study was to find the frequency and the causes that account for these fluctuations of Kt/V. Fifty-nine patients undergoing chronic HD were included in this prospective study. The results of monthly single pool Kt/V values were analyzed during a 6-month period. Duration of maintenance HD prior to the study was 4.49 +/- 3.6 (+/-SD) years. Any change of >0.2 from the previous 2-month average values was defined as abnormal. A total of 354 urea kinetic modeling sessions were recorded during 6 months in 59 patients. Of these, 38 (10.7%) met the criteria for abnormal value. Twenty-four measurements (6.7%) revealed lower while 14 (3.9%) demonstrated higher Kt/V values. Supervised sampling and conforming to the prescribed dialysis dose were applied for all abnormal measurements a week later. Among the group with lower Kt/V value, nine were due to noncompliance (shorter dialysis), four lower blood flow (Qb), four reversed needles, and one fistula thrombosis. Finally, in six cases no problem could be identified and a repeat measurement failed to document lower values. In the high-value group, nine cases were expected as there was an effort to increase dialysis dose prescription while five cases were due to false postdialysis sampling ("venous samples"). Overall, 29/354 (8.1%) measurements were in real disagreement with dialysis prescription. Lower-than-expected values are quite often due to reduced blood processing (shorter dialysis, lower Qb, and recirculation) and higher values due to inaccurate postdialysis sampling. Any possible pitfall in Kt/V measurements should be investigated before changing dialysis prescription in a stable HD patient.

Renal-portal shunt ameliorates renovascular hypertension in pigs.

BACKGROUND: Renovascular hypertension is the most common curable form of secondary hypertension. Renin angiotensin system activation depends on the balance between renin production by the kidney and renin degradation by the liver. Thus, we aimed to examine whether deviation of renin-rich blood from the affected kidney into the portal circulation (portalization) can ameliorate renovascular hypertension. METHODS: We selected a porcine model of unilateral renal artery stenosis because the pig's anatomy and physiology are comparable to those of humans and because pigs have already been found capable of developing chronic renovascular hypertension. Angiography and ultrasonography were deliberately used to evaluate renal artery stenosis and the renal-portal shunt. Histology was used to examine the effects of portalization on the kidney and liver after a period of two months. RESULTS: As expected, following the creation of a left renal artery stenosis both renin activity and mean blood pressure measurements increased from 1.23 +/- 0.06 ng/mL/h and 85.6 +/- 0.5 mm Hg at baseline to 4.59 +/- 0.02 ng/mL/h and 126 +/- 1.76 mm Hg, respectively. After portalization renin activity returned to the normal range (1.59 +/- 0.07 ng/mL/h) followed by a concomitant reduction of mean blood pressure to 91 +/- 2 mm Hg. Moreover, a significant correlation was observed between changes in renin activity and blood pressure measurements during the two stages of the experiment. Both the kidney and liver remained macroscopically and microscopically intact at the end of the experiment. CONCLUSION: Portalization of the affected kidney can ameliorate renovascular hypertension and therefore, it might be of benefit in those individuals with fibromascular or atheromatous lesions in the renal artery or its branches not amenable to balloon angioplasty or surgical revascularization.

Posttransplant erythrocytosis.

Posttransplant erythrocytosis (PTE) is defined as a persistently elevated hematocrit to a level greater than 51% after renal transplantation. It occurs in 10% to 15% of graft recipients and usually develops 8 to 24 months after engraftment. Spontaneous remission of established PTE is observed in one fourth of the patients within 2 years from onset, whereas in the remaining three fourths it persists for several years, only to remit after loss of renal function from rejection. Predisposing factors include male gender, retention of native kidneys, smoking, transplant renal artery stenosis, adequate erythropoiesis prior to transplantation, and rejection-free course with well-functioning renal graft. Just as in other forms of erythrocytosis, a substantial number (approximately 60%) of patients with PTE experience malaise, headache, plethora, lethargy, and dizziness. Thromboembolic events occur in 10% to 30% of the cases; 1% to 2% eventually die of associated complications. Posttransplant erythrocytosis results from the combined trophic effect of multiple and interrelated erythropoietic factors. Among them, endogenous erythropoietin appears to play the central role. Persistent erythropoietin secretion from the diseased and chronically ischemic native kidneys does not conform to the normal feedback regulation, thereby establishing a form of "tertiary hypererythropoietinemia." However, erythropoietin levels in most PTE patients still remain within the "normal range," indicating that erythrocytosis finally ensues by the contributory action of additional growth factors on erythroid progenitors, such as angiotensin II, androgens, and insulin-like growth factor 1 (IGF-1). Inactivation of the renin-angiotensin system (RAS) by an angiotensin-converting enzyme (ACE) inhibitor, or an angiotensin II type 1 AT1 receptor blocker represents the most effective, safe, and well-tolerated therapeutic modality.

Safety and efficacy of off-pump coronary artery bypass grafting in chronic dialysis patients.

Off-pump coronary artery bypass grafting (CABG) has been recently revived, because cardiopulmonary bypass (CPB) appears to worsen the multiple organ dysfunction after conventional CABG. To evaluate the safety and efficacy of the off-pump CABG in chronic dialysis patients, we compared the perioperative morbidity and mortality between 15 dialysis patients who underwent off-pump CABG at our center over the past 8 years with that of a concurrent group of 19 patients who underwent conventional CABG. Patients were selected for off-pump CABG only when complete revascularization was technically feasible. We found that off-pump CABG is as safe and effective as conventional CABG in selected dialysis patients. It might even be beneficial, because it is associated with less hematocrit drop and blood product use, a lower catabolic rate, and fewer dialysis requirements after surgery. However, the impact of off-pump technique on the long-term clinical outcome and resource utilization in renal patients requires further investigation.

Telematics Service for Home and Satellite Hemodialysis.

Home hemodialysis (HD) for the treatment of end-stage renal disease was first implemented about 30 years ago. In this paper the application of telematics monitoring services for supporting patients who need home HD or satellite HD is described. Two modified HD machines were located in two renal units, and a central control station (CCS, UNIX workstation with multimedia PC terminal) was located in another room of the hospital. Bidirectional communication between the modified HD machines and the CCS was managed using ISDN (Integrated Services Digital Network) links. Nine patients had 150 HD sessions performed using these HD machines over a period of 5 months. This system, called the HOMER-D system, provided on-line, remote supervision of the HD machine-related functions and the clinical condition of the patients through measurement of blood pressure, pulse rate, PO2 (pulse oxymetry), and ECG from the CCS. Any disturbances in the functioning of the HD machines were both visible and audible in the CCS, and the observer could give teleconsultation to the renal unit staff. No major dialysis-associated complications were observed; all data and alarms were transmitted correctly; and patients received adequate HD treatment.