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Biomedical subjects

E J Will

Publications and source records attributed to E J Will.

At least 37 records · Page 2Linked to original sources
PubMed1998

Assessment of ultrasound guided percutaneous ethanol injection and parathyroidectomy in patients with tertiary hyperparathyroidism.

BACKGROUND: Tertiary hyperparathyroidism continues to cause significant morbidity in patients with chronic renal failure. This is frequently resistant to medical management and may ultimately require a surgical parathyroidectomy. Recent studies have reported upon the technique of percutaneous ethanol ablation for both primary and tertiary hyperparathyroidism. In this study we report on a 5 year experience using ethanol injection and compare the results with surgical parathyroidectomy. METHODS: A prospective study in 39 patients with tertiary hyperparathyroidism, 25 were dialysis dependent and 14 had a functioning renal allograft. Twenty-two patients underwent percutaneous fine needle ethanol injection (PFNEI) and 17 underwent surgical parathyroidectomy. RESULTS: A > 30% reduction in intact parathyroid hormone (iPTH) was achieved in 11 of 22 patients undergoing PFNEI after a mean of 1.8 +/- 1.4 injections per gland. In four patients, symptomatic hyperparathyroidism recurred and they required further PFNEI or surgical parathyroidectomy at 17, 28, 46, and 48 months later. There was no significant reduction in iPTH in 11 patients following PFNEI after a mean of 2.5 +/- 1.3 injections per gland. They all required a subsequent surgical parathyroidectomy for symptomatic hyperparathyroidism. Four patients developed a laryngeal nerve palsy following PFNEI, two of which were permanent. Seventeen patients underwent successful surgical parathyroidectomy as a primary procedure. CONCLUSION: Whilst PFNEI is successful in primary hyperparathyroidism, when typically only one adenoma is present, the effectiveness of PFNEI is unpredictable and the long term results are poor compared with those of surgical parathyroidectomy in tertiary hyperparathyroidism. The procedure is not without complications and makes subsequent surgery more difficult. Therefore it can only be recommended for patients with a known single parathyroid gland such as patients in whom hyperparathyroidism has recurred following a previous surgical subtotal parathyroidectomy and who are unsuitable for further surgery.

Administration, Cutaneous↗
PubMed1998

Extracellular fluid volume determined by bioelectric impedance and serum albumin in CAPD patients.

AIM: To investigate the relationship between serum albumin and extracellular fluid volume, as measured by multifrequency bioelectrical impedance, in stable patients treated by CAPD. METHOD: Fifty-nine stable CAPD patients were assessed. Serum albumin (bromocresol green) and CRP, age, dialysate to plasma (D/P) creatinine ratio, normalized protein catabolic rate (nPCR), daily urine and peritoneal protein losses, and extracellular fluid volume (Vecf) were measured in each patient. Vecf was calculated as a percentage of actual body weight (Vecf% ABW), of lean body mass derived from anthropometry (Vecf% LBM) and of total body water (Vecf% Vtbw). Comparisons between those with a normal serum albumin (> or = 37 g/l) and those with a low serum albumin (< 37 g/l) were made by Mann-Whitney U test. Correlations with serum albumin were sought by Pearson's test. RESULTS: The D/P creatinine ratio, daily peritoneal and urine protein losses, and extracellular fluid volume (Vecf% LBM and Vecf% Vtbw) were all significantly greater in patients with serum albumin < 37 g/l as compared to those > or = 37 g/l; P < 0.05. Age, CRP, and nPCR were not different. Serum albumin was negatively correlated with Vecf% LBM, r = -0.25; P = 0.05, Vecf% Vtbw, r = -0.39; P = 0.002, and daily urinary albumin loss, r = -0.25, P = 0.06. CONCLUSION: Hypoalbuminaemia is partly dependent on subclinical overhydration in CAPD patients. Serum albumin is negatively correlated with increased extracellular fluid volume and the proportion of Vecf to Vtbw is increased in hypoalbuminaemic patients. Multifrequency bioelectrical impedance is able to identify these abnormalities.

Adult↗
PubMed1998

Simulating the effect of exercise on urea clearance in hemodialysis.

A two-compartment model of urea kinetics during hemodialysis is used to predict the effect of exercise on hemodialysis dose. It is assumed that the two compartments represent tissues that are perfused by low and high blood flows (initially 1.1 L/min and 3.8 L/min). The effect of changing the distribution of flows between the compartments, emulating the effect of exercise, is simulated using the model equations for a range of dialyzer clearances. Compartmental volumes are assumed constant (33.4 L and 8.6 L for low- and high-flow compartments, respectively). The analysis identifies muscle perfusion as a rate-limiting factor during the later stages of hemodialysis and illustrates the benefit of exercise during this phase in increasing dialysis efficiency. The model suggests that the postdialysis rebound in the blood urea concentration is eliminated by increasing flow to the low-flow compartment from 1.1 L/min to 7.1 L/min and sustaining this for at least 30 min of a 150-min dialysis session, independent of the dialyzer clearance. Additional exercise will not increase the dialysis dose. Experimental studies are required to confirm the analysis.

Computer Simulation↗
PubMed1998

Target practice.

Explore the source record for details and available documents.

Guidelines as Topic↗
PubMed1997

Assessment of nutritional status in CAPD patients: serum albumin is not a useful measure.

INTRODUCTION: In CAPD patients serum albumin is frequently used as an index of nutritional status, although it is recognized that hypoalbuminaemia may be caused by many factors. We have further examined the relationship between serum albumin and nutrition. METHODS: Nutritional status was assessed by biochemistry, anthropometry, mid-arm muscle circumference, muscle strength (hand grip and back), and lean body mass (from anthropometry, creatinine kinetics and bioimpedance) in a group of 76 stable CAPD patients. Correlations between biochemical and nutritional parameters were sought and data were compared between patient groups defined by serum albumin (> or = 37 vs < 37 g/l on two occasions 2 months apart) and separately according to subjective global assessment score (normal nutrition, A vs mild to moderate, B, and severe, C, malnutrition). RESULTS: In patients with a low SGA score, actual body weight, body mass index, mid-arm muscle circumference, lean body mass, subscapular skinfold thickness, hand grip strength (males and females) and iliac and triceps skinfold thicknesses and back strength (females only) were all significantly less than in patients with a normal SGA score. In contrast, none of these variables differed in either gender when patients were compared according to serum albumin. Serum albumin was correlated with serum creatinine (r = 0.45, P = 0.01), daily urine protein excretion (r = -0.42, P = 0.02) and uncorrected weekly creatinine clearance (r = -0.39) in females, but not with any index of body composition in either gender. CONCLUSION: Whilst SGA identified a patient group with significantly abnormal body mass, muscle mass and muscle strength, serum albumin did not. Serum albumin is not a useful marker of malnutrition in stable patients on CAPD.

Adolescent↗
PubMed1995

Risk of neoplasia in renal transplant patients.

Renal allograft recipients are at an increased risk of neoplasia, although the extent of the problem has not been established in a typical European transplant population. To assess this risk we did a comprehensive, retrospective study of 918 patients transplanted at one centre over 24 years. The centre (Leeds) serves Yorkshire and Humberside, a region in northern England with a population of 3.6 million. The search, which made use of six sources of information, revealed 70 patients (7.6%) who had developed a neoplastic lesion, 10 patients having more than one type. More than half (42) were cutaneous lesions (mostly squamous cell carcinomas). The risk of developing neoplasia in the first 10 years after transplantation was calculated to be 14%. By 20 years this had risen to 40% compared with a 6% cumulative risk of neoplasia in an age-matched control population (p < 0.005). The full extent of this problem in the European transplant population has been underestimated and, now that recipients are surviving longer, there is a clear need for both lifelong surveillance and closer investigation of these patients.

Adult↗
PubMed1995

A mathematical analysis of a two-compartment model of urea kinetics.

A model of urea distribution comprising well-mixed intracellular and extracellular compartments, with diffusive transfer of urea between compartments, is used to study blood urea variation during haemodialysis. Assuming that a typical adult patient (weight 70 kg and urea generation rate 5 mg min-1) is dialysed using a high-efficiency dialyser (urea clearance 0.2- 0.251 min-1) at an ultrafiltration rate of 10 ml min-1, it is shown that a perturbation analysis can account for the effects of ultrafiltration and urea generation. This permits an analytical solution of the equations which describe the variation in solute concentration in each of the compartments, which may be compared with the solution obtained when urea generation and ultrafiltration are neglected. For a typical adult patient with urea distribution volume in the range 25-40 l undergoing high-efficiency haemodialysis, the analysis suggests that the contribution of ultrafiltration to the variation in urea concentration during dialysis is similar in magnitude to the experimental errors in measuring the blood concentration of urea and that a constant volume model will be sufficiently accurate to describe urea clearance in many patients.

Adult↗
PubMed1995

Quantitative reticulocyte analysis may be of benefit in monitoring erythropoietin treatment in dialysis patients.

Reticulocyte responses to low-dose erythropoietin (EPO) were monitored using automated flow cytometric analysis. Sixteen adult dialysis patients were treated with 1,000 U of recombinant human EPO (rHuEPO), subcutaneously, thrice weekly (mean dose 15.7, SD 3.7 U/kg). The reticulocyte count (baseline 31.1, SD 19.1 x 10(9)/L) increased in 14 patients in the first week, with a peak response occurring at Week 2 (mean 57.3, SD 26.5 x 10(9)/L, p < 0.01). There was a wide spectrum of response, the maximal absolute increment ranging from 6.8-69.7 x 10(9)/L (maximal percentage increase 19-863%). Overall there was no relationship between the early increment in reticulocyte count and hemoglobin (Hb) response over the ensuing 4 months. Nine patients became transfusion independent (mean Hb increasing from 6.9, SD 0.8-9.2, SD 1.2 g/dl). Two patients had poor reticulocyte increments and no significant change in Hb. The remaining 5 patients responded partially with a brisk reticulocyte response and a marked reduction in transfusion dependency, but without a sustained increase in Hb. On investigation, all had gastrointestinal bleeding (melena in 1, commencing after initiation of treatment, positive fecal occult bloods in 4), whereas none of the other patients showed evidence of blood loss. It is notable that the erythron was sensitive to this modest dose of rHuEPO in the majority of patients as evidenced by the reticulocyte response. The results provide useful information in the management of patients on rHuEPO. A small or inapparent reticulocyte response suggests a confounding factor; a poor Hb response in the presence of active reticulocyte synthesis points to occult blood loss or hemolysis.

Adult↗
PubMed1995

Re-establishment of erythropoietin responsiveness in end-stage renal failure following renal transplantation.

Re-establishment of erythropoietin (EPO) secretion following renal transplantation is poorly understood. The development of sensitive EPO radioimmunoassay has enabled further study of this phenomenon. Forty-one adult patients were studied during the first 16 weeks following renal transplantation. Twenty six received cyclosporin monotherapy and 15 also received prednisolone and azathioprine. Serum creatinine, haemoglobin (Hb), ferritin and EPO were assayed pre-operatively, daily for 1 week, weekly for 1 month, and fortnightly to 16 weeks. An expected EPO value, for any Hb level, was derived by linear regression analysis in 144 patients with iron deficiency anemia. An observed to expected ratio (O/E) was calculated, a value of 1.0 implying appropriate responsiveness. Hb increased from 8.6 +/- 2.0 (SD) to 12.3 +/- 2.1 g/dl (p < 0.001) over 16 weeks, an increase unaffected by ferritin status. Mean EPO concentration increased during the first week with a peak at day 4 (22.1 +/- 13.3 to 44.6 +/- 40.0 mu/ml, p < 0.05), a change apparent only in patients with immediate graft function (24 cases). There was no correlation between EPO and Hb pre-operatively; however a significant inverse relationship was established by week 16 (r = -0.404, p < 0.02). The median O/E ratio (0.22) at baseline increased progressively to 1.0 at 16 weeks (p < 0.001); ratios were significantly greater in the immediate versus delayed function group throughout (p < 0.05). In the former group an O/E ratio of 1.0 was reached at 10 weeks when mean serum creatinine was 142 +/- 48 mumol/l. Patients with poor ongoing renal function (9 cases, serum creatinine > 250 mumol/l at 16 weeks) had impaired Hb recovery (10.1 +/- 1.6 vs 12.7 +/- 2.0 g/dl at 16 weeks, p < 0.05). EPO values were not different in those patients but median O/E ratios were significantly depressed (p < 0.05) throughout, the maximum O/E ratio being 0.75. Recovery of renal function is accompanied by a beneficial Hb response driven by EPO synthesis in the transplant. The O/E ratio provides a useful index to assess EPO responsiveness. Appropriate secretion was achieved during the first 4 months and optimized by immediate and satisfactory graft function.

Adult↗
PubMed1995

The correlation between protein catabolic rate and Kt/V in hemodialysis is not a mathematical artifact.

To test whether the demonstrated correlation between Kt/V urea and normalised protein catabolic rate (NPCR) is caused by a mathematical artifact, we examined 12 adult and 8 paediatric haemodialysis patients. Kt/V was determined by the classical method. As an equivalent of NPCR we measured normalised urea generation rate (NUGR) by a one-week collection of dialysate and urine using total body water estimated by bioelectrical impedance for normalisation. The correlation between Kt/V and NUGR was 0.58 (all), 0.55 (adults), and 0.62 (children). Since the determination of Kt/V and NUGR are not interdependent, we conclude that the correlation between Kt/V and protein catabolism is not artifactual.

Adolescent↗
PubMed1994

A comparison of molecular clearance rates during continuous hemofiltration and hemodialysis with a novel volumetric continuous renal replacement system.

We developed a continuous, volumetrically controlled veno-venous renal replacement system that can be operated in filtration or dialysis modes. We compared the clearances of substances with a range of molecular weights (MW) in each mode. Ten patients with acute renal failure underwent serial postdilutional hemofiltration and hemodialysis, for 30 min each, in sequence and in randomized order. All were receiving vancomycin for concurrent sepsis. The system incorporated a Filtral 10 AN69 artificial kidney; blood flow rate was 200 ml/min, and dialysate/filtrate flow rate was 25 ml/min. Sieving (SC) and diffusion (DC) co-efficients, for hemofiltration and hemodialysis, respectively, were identical for urea (MW 60; 1.01 +/- 0.05 vs 1.01 +/- 0.07) and creatinine (MW 113; 1.00 +/- 0.09 vs 1.01 +/- 0.06), and clearance equated with dialysate/filtrate flow. There was a modest difference in uric acid clearance (MW 168; SC 1.01 +/- 0.04 vs DC 0.97 +/- 0.04; p < 0.05). Vancomycin (MW 1,800) removal was 19% greater during filtration compared with dialysis (SC 0.87 +/- 0.10 vs DC 0.74 +/- 0.06; p < 0.01). For small solutes, the two modalities were equivalent. Vancomycin clearance was appreciably greater with hemofiltration, which is consistent with a greater potential for convection-based therapy in the removal of uremic and other middle molecules.

Acute Kidney Injury↗
PubMed1994

Comparison of the use of standard heparin and prostacyclin anticoagulation in spontaneous and pump-driven extracorporeal circuits in patients with combined acute renal and hepatic failure.

Although prostacyclin has been reported to be an effective extracorporeal anticoagulant for intermittent haemofiltration and dialysis treatments, it has been suggested that it is inferior to heparin in preventing clotting in spontaneously driven continuous haemofiltration and/or dialysis circuits. We studied the effectiveness of both heparin and prostacyclin as anticoagulants in a variety of extracorporeal circuits in 17 patients with combined acute hepatic and renal failure who were at risk of haemorrhage. Although there were no differences in the pump-assisted extracorporeal circuits, prostacyclin was found superior to heparin during spontaneously driven continuous arteriovenous haemofiltration and/or dialysis. During some 2,600 h of prostacyclin therapy, there were only 3 episodes of haemorrhage that required blood transfusion compared to 8 major haemorrhages and 2 deaths from intracerebral haemorrhage during 600 h of anticoagulation with heparin. The median filter life was greater with prostacyclin, 60 h (42-72), compared to heparin, 8 h (4-16), p < 0.01. This study suggests that prostacyclin is superior to heparin in maintaining the integrity of a spontaneous arteriovenous extracorporeal circuit in patients at risk of major haemorrhage.

Acute Kidney Injury↗
PubMed1994

Haemodialysis recirculation measured using a femoral artery sample.

The traditional method for measuring vascular access recirculation has been questioned. We have compared methods based on samples from the femoral artery, a peripheral vein, and a slow flow technique. Seventeen patients on high-flux haemodialysis with blood flow 355 +/- 42 ml/min were examined after 60 min of treatment. Using urea as the marker solute, recirculation was 0.0 +/- 1.8% (femoral artery), 6.7 +/- 2.7% (peripheral vein), and 4.7 +/- 1.6% (slow flow), and using creatinine 0.1 +/- 1.4% (femoral artery), 7.8 +/- 3.0% (peripheral vein) and 2.9 +/- 1.2 (slow flow). Access recirculation was non-existent among these patients when using the femoral artery sample: maximum 3.1%. In contrast, the traditional method (peripheral vein) produced values up to 13.5%. The observed differences can be explained by cardiopulmonary recirculation. Blood returning from the periphery mixes with blood returning from the dialyser, so that solute concentration will be less in femoral artery than in peripheral vein. In conclusion, neither the traditional method nor slow-flow techniques accurately quantify access recirculation. Cardiopulmonary recirculation must be considered in kinetic studies, including routine dialysis prescription, where samples should be taken at least 2 min after termination of dialysis.

Blood Circulation↗
PubMed1993

Effect of aluminum mobilization on hemoglobin during the first six months after transplantation.

We prospectively monitored 38 patients for the first six months following successful renal cadaver allograft transplantation. Hemoglobin increased from a mean of 8.2 +/- 0.3 g/dl to 13.4 +/- 0.3 g/dl (SEM), P < 0.001, plasma aluminum decreased from 1.3 +/- 0.2 mumol/liter to 0.46 +/- 0.04 mumol/liter, P < 0.001, and urinary aluminum excretion which peaked at one week post-transplant, 5.5 +/- 1.3 mumol/24 hr decreased to 1.8 +/- 0.3 mumol/24 hr, P < 0.001. Prior to transplantation 22 patients had been prescribed aluminum-containing phosphate binders. Following transplantation this group had persistently greater plasma aluminum and urinary aluminum concentrations which were sustained throughout the study period, compared with those not given aluminum containing medicaments. Hemoglobin and iron status were similar in the two groups prior to transplantation, although red blood cell volume was smaller in those given aluminum-containing phosphate binders, 89 +/- 0.9 fl (fentoliters) versus 95 +/- 1.6 fl, P < 0.05. However, the percentage increase in hemoglobin following transplantation was greater in the group not given aluminum preparations, 34 +/- 4% versus 7 +/- 5% at one month, 69 +/- 7% versus 37 +/- 7% at three months, and 80 +/- 8% versus 56 +/- 8% at six months respectively, all P < 0.05. This study suggests that aluminum mobilization following successful renal transplantation may reduce the rate of hemopoiesis.

Adult↗