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Biomedical subjects

R Uldall

Publications and source records attributed to R Uldall.

At least 19 recordsLinked to original sources
PubMed1998

Control of serum phosphate without any phosphate binders in patients treated with nocturnal hemodialysis.

We compared the efficacy and the long-term effects of nocturnal hemodialysis (NHD) versus conventional hemodialysis (CHD) in controlling serum phosphate levels in patients with end-stage renal disease (ESRD). Patients underwent thrice weekly CHD and were subsequently switched to NHD six nights weekly. In the "acute" study serum and dialysate phosphate were measured during and after dialysis, and the total dialysate was collected to calculate mass solute removal. Although pre-dialysis (1.7 +/- 0.6 vs. 1.5 +/- 0.8 mM) serum phosphate levels were similar in CHD and NHD, respectively, post-dialysis levels were slightly lower with CHD (0.7 +/- 0.2 vs. 0.8 +/- 0.2 mM, P < 0.05). The measured phosphate removed per session of CHD or NHD was comparable, 25.3 +/- 7.5 versus 26.9 +/- 9.8 mumol/session, respectively. On the other hand, the cumulative weekly phosphate removal was significantly higher with NHD as compared to CHD, 75.8 +/- 22.5 versus 161.6 +/- 59.0 mumol/week (P < 0.01). In the "chronic" study serum phosphate levels were measured monthly for five months on CHD and for five months after the patients were switched to NHD. Dietary phosphate intake and the dosage of phosphate binders were tabulated. Serum phosphate levels fell during NHD: 2.1 +/- 0.5 mM at the beginning of the study and 1.3 +/- 0.2 mM five months after being switched to NHD (P < 0.001). At the same time dietary phosphate intake increased by 50%. By the fourth month of NHD therapy none of the patients was taking any phosphate binders. In conclusion, NHD is more effective in controlling serum phosphate levels than CHD, allowing patients to discontinue their phosphate binders completely and to ingest a more liberal diet.

Cross-Over Studies↗
PubMed1998

Nocturnal hemodialysis: three-year experience.

There is evidence that high frequency, as well as long duration, hemodialysis provides better clinical outcomes. We developed nocturnal hemodialysis, a new innovative form of renal replacement therapy, which is performed six to seven nights per week for 8 to 10 h during sleep at home. Blood flow was set at 300 ml/min and dialysate flow at 100 ml/min. An internal jugular catheter was used as the vascular access. Special precautions were taken to prevent accidental disconnection during sleep, as well as air embolization. Dialysis functions from the patient's home were monitored continuously via a modem at the nocturnal hemodialysis center. Twelve patients have completed training and have been successfully performing nocturnal hemodialysis for up to 34 mo. This study represents 170 patient months of experience accumulated over 3 yr. There was hemodynamic stability and significant subjective improvement in patient well being. Nightly Kt/V was 0.99. Weekly removal of phosphate was twice as high and beta2 microglobulin 4 times as high as conventional hemodialysis. All patients have discontinued their phosphate binders and have increased dietary phosphate and protein intake. BP control was achieved with fewer medications. Dialyzer reuse has decreased the operating costs to the level of the other form of home dialysis. Complications were infrequent and were related primarily to the dialysis access. Nocturnal hemodialysis represents the most efficient form of dialysis at low cost and should be considered as an option for patients who can be trained for home hemodialysis.

Adult↗
PubMed1996

Slow nocturnal home hemodialysis at the Wellesley Hospital.

To alleviate the overcrowding of in-center hemodialysis (HD) facilities, we have developed slow nocturnal home hemodialysis (SNHHD), an innovative form of renal replacement therapy. SNHHD is performed 5 to 7 nights/week for 8 hours, during sleep, with a blood flow of 300 mL/min and a dialysate flow of 100 mL/min. The vascular access is by means of the Uldall-Cook catheter, which allows for easy patient access with low infection rates. Special precautions were taken to prevent accidental disconnection during sleep. Dialysis functions were monitored via a modem from the patient's home to the SNHHD center and have proven valuable in increasing patient confidence. The removal of urea, phosphate, and B2 microglobulin (B2M) during 1 week of SNHHD greatly exceeds that of thrice weekly conventional HD. Five patients have completed training and have been successfully performing SNHHD for 6 to 16 months. All patients have discontinued phosphate binders and increased dietary phosphate intake. Four out of five patients report sleeping soundly and experience greatly increased energy and stamina. Repeated in situ reuse of the dialyzer and the blood lines will reduce the patients work and make SNHHD a very inexpensive modality.

Adult↗
PubMed1995

Lack of enhanced T-helper cell function in uremic patients with circulating alloreactive antibodies.

Some uremic patients with a history of blood transfusion, pregnancy, and previous transplantation maintain high levels of alloreactive cytotoxic antibodies in the absence of continuous exogenous allogenic stimuli and are thus considered sensitized to the major histocompatibility proteins. To differentiate into antibody-producing cells, B lymphocytes must interact with T-helper (CD4+) cells. Whether ongoing help from these cells is necessary for the B cells to continue producing cytotoxic alloreactive antibodies in these sensitized uremic patients is unknown. To gain insight into the cellular mechanisms that are associated with sustained alloantibody production, T cell activation markers were measured and specific and nonspecific T-helper cell function was studied in three uremic groups with different levels of panel reactive antibodies: 10 patients whose sera reacted to more than 80% of a panel of normal lymphocytes for at least 6 months before the study were highly sensitized, 20 patients whose sera reacted to less than 80% of the panel were moderately sensitized, and 10 nonsensitized patients whose sera did not react to any cell on the panel. The number of total and activated T-helper cells was similar in the highly sensitized and nonsensitized patients. Peripheral blood lymphocyte proliferation in response to plant lectins, soluble OKT3, or alloantigens was similar in the three uremic groups. The spontaneous proliferation of pure T-helper cells and proliferative responses to immobilized OKT3 or alloantigens were also similar in highly sensitized and nonsensitized patients. Alloreactive interleukin-2-producing cell frequencies with pure CD4+ cells as responding cells were 771 +/- 77.9/10(6) cells in highly sensitized, 945 +/- 252/10(6) cells in nonsensitized, and 973 +/- 114/10(6) cells in controls (P = not significant). Panel reactive antibody levels did not correlate with any of the measures of T helper responses. There was a significant decrease of peripheral blood lymphocyte responses to alloantigens and anti-CD3 antibody in all uremic patients as compared with normals, suggesting a dysfunction in accessory cells that was quantitatively similar in sensitized and nonsensitized patients. In spite of the continuous production of alloantibodies by B cells, there is no evidence of either specific or nonspecific enhancement of T-helper cell function in sensitized patients. The absence of T cell immunity to alloantigens suggests that sustained activation of T-helper cells with subsequent interleukin-2 production is not necessary to maintain alloreactive B cell function.

Adult↗
PubMed1994

Dialyser reuse: an automated system using peracetic acid.

For 3 years starting in April 1989, in a 17-station, in-centre haemodialysis unit at the Toronto Western Hospital, re-use of dialysers was performed using the Renatron-2 Dialyser Reprocessing System with peracetic acid as a sterilant. During this period 40,234 treatments were carried out and dialysers were used an average of 4.2 times. Net savings, after taking into account the total costs of re-use, averaged Can $309,000,000 per year. There were no deaths and no discernible morbidity attributable to the practice of re-use. We conclude that dialyzer re-use is an effective way to reduce the costs of haemodialysis and is entirely safe providing that it is carried out properly.

Canada↗
PubMed1993

A new vascular access catheter for hemodialysis.

A new vascular access catheter has been developed (Cook Critical Care, Bloomington, IN) that is suitable for both short-term and long-term hemodialysis. Designed primarily for the internal jugular vein, it emerges through a subcutaneous tunnel on the anterior chest wall. With parallel cylindrical lumens to provide blood flows of 400 mL/min, it is compressible during insertion and can be placed percutaneously in the vein through a 13-French peel-away sheath. This allows repeated insertions at different times in the same patient. In 80 catheter insertions, we have found one case of jugular vein thrombosis attributable to the catheter and no subclavian vein thrombosis. After 15 months of use, the bloodstream infection rate was one per 19.7 patient-months. Using this device, it should be possible to stop the subclavian vein damage and perforating injuries that have been the most important complications of semistiff, tapered, subclavian catheters.

Adult↗
PubMed1993

Superior vena cava stenosis associated with hemodialysis catheters.

The cases are described of four patients on long-term hemodialysis who developed stenosis of the superior vena cava (SVC) that interfered with the functioning or placement of jugular catheters for hemodialysis. All four patients had previously received multiple subclavian and/or jugular catheters inserted for hemodialysis access. In three patients, the SVC stenosis was successfully dilated by balloon angioplasty, and in one of these a stent was inserted to prevent restenosis. These three patients have subsequently been successfully dialyzed with jugular catheters. Stenosis of the SVC should be suspected when jugular catheters in the SVC give inadequate flows in the absence of thrombotic obstruction. Balloon dilatation with or without vascular stenting may allow satisfactory vascular access to be reestablished.

Aged↗
PubMed1993

Maintaining the patency of double-lumen silastic jugular catheters for haemodialysis.

A system has been developed for maintaining the patency of double lumen silastic jugular catheters in patients with refractory vascular access problems. Most patients receive a small daily dose of aspirin. Selected patients also receive warfarin to maintain a prothrombin time (PT) of 15, 20, or 30 seconds. Inadequate blood flow due to thrombus obstruction can be overcome by the intravenous administration of urokinase, 250.000 units. This can be administered safely to outpatients provided that heparin is not given simultaneously. Occasionally a second dose may be required. By adopting this policy all catheter obstructions have been overcome. The danger of iatrogenic bleeding cannot be discounted. Warfarin therapy must be very closely monitored.

Aspirin↗
PubMed1992

An enzymatic method for measuring serum mannitol and its use in hemodialysis patients.

We evaluated two chemical methods for quantifying mannitol in serum, based on the oxidation of mannitol by periodate, and measurement of the formaldehyde formed with chromotropic acid (colorimetry) or acetylacetone (fluorometry). We found interference in these methods by serum glycerol. Additionally, a high-performance liquid chromatography (HPLC) method was evaluated and found to be specific but impractical for routine use. We therefore, developed an enzymatic fluorometric procedure, based on the oxidation of mannitol by beta-NAD to fructose and NADH, in the presence of the enzyme mannitol dehydrogenase (MD). MD is not commercially available and was partially purified from cultures of Leuconostoc mesenteroides. This new method is specific, sensitive, simple, and accurate and is proposed as the method of choice for measuring mannitol in the serum of patients who received this sugar alcohol during routine hemodialysis treatment.

Chromatography, High Pressure Liquid↗
PubMed1992

The use of nuclear magnetic resonance imaging in monitoring total body iron in hemodialysis patients with hemosiderosis treated with erythropoietin and phlebotomy.

Two hemodialysis patients with hemosiderosis were treated with combined erythropoietin and repeated phlebotomy. Serial nuclear magnetic resonance (NMR) imaging and serum ferritin levels were used to monitor the efficacy of treatment. This treatment modality has definite advantages over chronic deferoxamine therapy. NMR image-derived parameters offer an objective, accurate, and noninvasive indication of tissue iron stores.

Adult↗
PubMed1991

Septicemia in long-term jugular hemodialysis catheters; eradicating infection by changing the catheter over a guidewire.

By convention, septicemia occurring from an infected vascular catheter is treated with antibiotics and removal of the catheter. This approach, used with surgically implanted long-term catheters would be expected to result in loss of the vascular access site. During a 57 month period, we treated 21 episodes of septicemia secondary to infection of long term indwelling double lumen jugular venous catheters in our hemodialysis unit. Seventeen of 21 episodes were managed successfully by changing the catheter over a guidewire, thus preserving the access site. No relapse was observed after the antibiotic therapy was stopped. Only four patients required complete removal of the catheter and subsequent use of another site.

Actuarial Analysis↗
PubMed1988

Simultaneous aortic and renal artery reconstruction for acute arterial occlusion in solitary kidney.

A case is described of the onset of acute renal failure due to renal artery occlusion in a solitary kidney of a sixty-six-year-old woman. She had been treated for severe hypertension due to renal artery stenosis. An aortorenal bypass to revascularized the kidney was combined with repair of an abdominal aortic aneurysm. There was early and full recovery of renal function in the single kidney, and the patient was completely rehabilitated. Review of the literature shows that an aggressive surgical approach to the management of renal artery occlusion is usually followed by excellent results. The pre-existence of renal artery stenosis encourages the formation of a collateral arterial supply which maintains the nutrition of the kidney almost indefinitely, after renal artery occlusion. Revascularization will result in prompt recovery of renal function.

Acute Kidney Injury↗
PubMed1985

Prevention of thrombosis in arteriovenous fistulas.

To prevent thrombosis in arteriovenous fistulas it is necessary to obtain the knowledgeable cooperation not only of the whole health care team, but also of the patient. The first step is preservation of forearm veins by avoiding unnecessary venipunctures in patients with chronic renal failure. Fistulas should be constructed well in advance of need and use natural rather than prosthetic veins whenever possible. Major surgery elsewhere is a potential cause of fistula thrombosis. Fistula construction is often best delayed till major surgery is over and until the veins have recovered from the effects of systemic steroid therapy. Avoidance of premature fistula cannulation and correct needling techniques help to prevent vein wall damage. Alertness to the presence of high venous pressures on dialysis and observation of inefficient dialysis due to recirculation should lead to detection of narrowed segments which can be surgically corrected before thrombosis occurs. Antiplatelet drugs are of proven value in the prevention of recurrent thrombotic episodes.

Arteriovenous Shunt, Surgical↗