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Alfred K Cheung

Publications and source records attributed to Alfred K Cheung.

46 records · Page 3Linked to original sources
PubMed2002

Impact of renal failure on the risk of myocardial infarction and death.

BACKGROUND: It is unclear whether pre-existing cardiovascular disease or predisposition of the uremic state leads to the high cardiovascular morbidity and mortality associated with renal failure. We examined whether renal failure independently increases the risk of myocardial infarction and death. METHODS: A total of 8600 patients with variable glomerular filtration rate (GFR) at the time of coronary angiography participated in the Intermountain Heart Study. Coronary disease was defined as >or=70% stenosis. Modification of Diet in Renal Disease formula was used to calculate glomerular filtration rate (GFR). Cox regression models were used to compare outcomes. RESULTS: The mean GFR was 71 +/- 24 mL/min. There were 1320 (15%) deaths, 657 (9%) myocardial infarctions and 1776 (21%) death or myocardial infarctions over 3.2 +/- 1.9 years. Compared to the highest GFR quartile, the lowest GFR quartile (mean GFR 41 +/- 14 mL/min) was associated with higher risk for myocardial infarction (RR 1.43, 95% CI 1.15 to 1.78), death (RR 2.77, 95% CI 2.32 to 3.30) and death/myocardial infarction (RR 2.13, 95% CI 1.85 to 2.45) in multivariable models adjusted for age, sex, hypertension, hyperlipidemia, smoking, family history of coronary disease and diabetes. Even after further adjustment for coronary angiographic data and the choice of initial therapy, lowest GFR quartile was associated with increased risk of myocardial infarction (RR 1.51, 95% CI 1.21 to 1.88), death (RR 2.60, 95% CI 2.18 to 3.10) and death/myocardial infarction (RR 2.08, 95% CI 1.80 to 2.39). CONCLUSIONS: Even moderate renal failure increases the risk of myocardial infarction and death independent of clinical variables, baseline angiographic evidence of coronary disease and therapy.

Aged↗
PubMed2002

Association of serum albumin and atherosclerosis in chronic hemodialysis patients.

BACKGROUND: Because cardiovascular disease is the leading cause of death and hypoalbuminemia predicts mortality, hypoalbuminemia may be associated with atherosclerosis. METHODS: In 1,411 patients enrolled in the HEMO study, associations of albumin with the presence of coronary artery disease (CAD), cerebrovascular disease (CVD), peripheral vascular disease (PVD), and any one of the three conditions at baseline were examined using multivariable logistic regression models. RESULTS: In the two-slope model, when albumin level was 3.6 g/dL (36 g/L) or greater, with each 1-g/dL (10-g/L) increase in albumin level the odds for CAD (odds ratio [OR], 0.32; 95% confidence interval [CI], 0.17 to 0.59), PVD (OR, 0.39; 95% CI, 0.18 to 0.80), CVD (OR, 0.33; 95% CI, 0.15 to 0.73), and any one of the three conditions (OR, 0.23; 95% CI, 0.12 to 0.44) decreased. When albumin level was less than 3.6 g/dL (36 g/L), none of the conditions was statistically significantly associated with each 1-g/dL (10-g/L) increase in albumin level. When normal- and low-albumin groups were compared with each other, patients with albumin levels less than 3.6 g/dL (36 g/L) had a higher association with CAD (OR, 1.32; 95% CI, 1.03 to 1.70) and for any one of the three conditions (OR, 1.38; 95% CI, 1.07 to 1.78). CONCLUSION: The odds for atherosclerosis linearly decreased as albumin level increased in the normal-albumin group, and a plateau was seen in the low-albumin group; however, the low-albumin group had significantly greater CAD. The nonlinearity of association of albumin level with prevalence of atherosclerosis might be due to the cross-sectional nature of the study of higher mortality with hypoalbuminemia.

Arteriosclerosis↗
PubMed2002

Computer simulation of small-solute and middle-molecule removal during short daily and long thrice-weekly hemodialysis.

BACKGROUND: More intensive hemodialysis (HD) regimens (short daily and long thrice-weekly HD) provide potential opportunities for improved patient outcome. An adequate dialysis dose for these regimens cannot be established from the existing literature. METHODS: Using computer simulation, we compared conventional HD with short daily HD and long thrice-weekly HD using two dose measures of solute clearance: equivalent renal clearance (EKR) and a generalized standard Kt/V (stdKt/V) for urea, creatinine, vitamin B12, inulin, and beta2-microglobulin. Solute kinetics were simulated using a variable-volume two-compartment mathematical model. RESULTS: Calculated EKR values were greater during short daily HD compared with those during conventional HD by 16.9%, 15.5%, 16.1%, 5.2%, and 2.5% for urea, creatinine, vitamin B12, inulin, and beta(2)-microglobulin, respectively. Calculated stdKt/V values predicted more substantial increases in dose for all solutes. Increasing the time of dialysis from 4 to 8 hours three times weekly resulted in substantially greater stdKt/V and EKR values compared with both conventional and short daily HD. Solute clearances during short daily HD could be enhanced to approach those during long HD if treatment time was increased or very high surface area dialyzers were used with very high blood flow rates. CONCLUSION: Dose measures for all molecules larger than urea increase with either increased frequency or, even more so, increased duration of dialysis. Prediction results of these models require confirmation in clinical studies. Furthermore, the relationship between increased dialysis dose and long-term clinical outcome during more intensive HD regimens requires examination in clinical trials.

Computer Simulation↗
PubMed2002

Seasonal variations in clinical and laboratory variables among chronic hemodialysis patients.

Seasonal variations in BP among chronic hemodialysis patients have been reported. It was hypothesized that other characteristics of these patients might also vary with the seasons. Twenty-one clinical and laboratory variables were examined for seasonal variations among 1445 patients enrolled in the Hemodialysis Study, sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases. Mixed-effects models were applied to longitudinal changes (up to 45 mo) for individual patients for 19 of the 21 variables, which were measured at least twice each year, to determine the seasonal component of each variable. Seasonal variations in the other two variables, i.e., protein and energy intakes determined from annual dietary records, were assessed in cross-sectional comparisons of intakes of patients entering the study at different time points. Thirteen of the 21 variables examined demonstrated statistically significant (P < 0.01) seasonal components in their longitudinal variations. Predialysis blood urea nitrogen concentrations peaked in March, which coincided approximately with the peak protein catabolic rates, as well as protein and energy intakes (determined by dietary recall). Predialysis systolic and diastolic BP values were highest in winter and lowest in summer, corroborating previous reports. In addition, the lower predialysis BP values in summer were associated with higher outdoor temperatures and less interdialytic fluid gain. The mean predialysis hematocrit values were highest in July, which could not be attributed solely to the estimated changes in plasma volume. Seasonal variations in clinical and laboratory variables occur commonly among chronic hemodialysis patients. The reasons for most of these variations are not apparent and require further investigation. Nonetheless, failure to consider these variations might lead to biases in the interpretation of clinical studies. In addition, awareness of these variations might facilitate the interpretation of laboratory results and the clinical treatment of these patients.

Adult↗
PubMedDate not supplied

Hollow fiber shape alters solute clearances in high flux hemodialyzers.

The mass transfer properties of hemodialyzers containing hollow fiber membranes are known to be influenced by membrane chemical composition, surface area, and pore size; however, the effects of hollow fiber shape (or configuration) and packing density within the dialyzer housing have not been well characterized. We determined, both in vitro and ex vivo (clinical), solute clearances and mass transfer-area coefficients (KoA) for high flux dialyzers containing polysulfone hollow fibers of identical chemical composition but different shapes. Hemoflow F80A (1.8 m2 of membrane surface area) dialyzers contained hollow fibers with a conventional shape, but Optiflux F180A (1.8 m2), F200A (2.0 m2), and F200NR (2.0 m2) dialyzers contained hollow fibers with a wavy shape. Clearances and KoA values determined in vitro for urea and creatinine increased with increasing dialysate flow rate and were higher for Optiflux F180A and F200A dialyzers than for Hemoflow F80A dialyzers. In vitro clearances for lysozyme and myoglobin were also higher for Optiflux F180A and F200A dialyzers than for Hemoflow F80A dialyzers, suggesting that a wavy hollow fiber shape increases mass transfer by increasing effective membrane surface area, conceivably by altering dialysate flow patterns. Urea clearances and KoA values determined ex vivo were higher for Optiflux F200NR dialyzers than for Hemoflow F80A dialyzers, confirming that the in vitro results are applicable to clinical hemodialysis. These increases in mass transfer efficiency for dialyzers containing hollow fibers with a wavy shape are consistent with improved mass transfer within the dialysate compartment as evidenced by the manufacturer-reported dialysate pressure-flow relationships. We conclude that the mass transfer characteristics of high flux dialyzers can be altered by the shape of the hollow fibers.

Biocompatible Materials↗
PubMedDate not supplied

Dialyzer performance in the HEMO Study: in vivo K0A and true blood flow determined from a model of cross-dialyzer urea extraction.

Inlet and outlet blood urea concentrations (Cin and Cout) can be used to directly measure dialyzer performance if simultaneous blood flow measurements (Qb) are available. Dialyzer clearance, for example, is the product of the urea extraction ratio [ER = (Cin - Cout)/Cin] and Qb. Urea concentrations are measured routinely in all hemodialysis clinics, but Qb is usually reported as the product of the pump rotational speed and pump segment stroke volume, which can be inaccurate at high flow rates. Dialyzer urea extraction is also a function of Qb, dialysate flow (Qd), and the membrane permeability-area coefficient (K0A) for urea. To determine true in vivo values for Qb and K0A in the absence of direct flow measurements, we developed a model based on an existing mathematical equation for hemodialyzer ER under conditions of countercurrent flow. Qb, K0A, and other variables were adjusted to fit the modeled ER to ER measured in 1,285 patients treated with Qb that ranged from 200 to 450 ml/min during the HEMO Study. Fitting was performed by least squares nonlinear regression using parametric and nonparametric methods for estimating true flow. As Qb rose above 250 ml/min, both methods for estimating actual Qb showed increasing deviations from the flow reported by the blood pump meter. Modeled values for K0A differed significantly among dialyzer models, ranging from 71% to 96% of the in vitro values. The previously described 14% increase in K0A, as Qd increased in vitro from 500 to 800 ml/min, was much less in vivo, averaging only 5.5 +/- 1.5% higher. Dialyzer reprocessing was associated with a 6.3 +/- 1.0% reduction in K0A and an approximate 2% fall in urea clearance per 10 reuses (p < 0.001). Multiple regression analysis showed a small but significant dialysis center effect on ER but no independent effects of other variables, including the ultrafiltration rate, diabetic status, race, ethnicity, sex, method of reuse, treatment time, access recirculation, and use of central venous accesses. The new algorithm allowed a more accurate determination of true Qb and in vivo K0A in the absence of direct flow measurements in a large population treated with a wide range of blood flow rates. Application of this technique for more than 1000 patients in the HEMO Study confirmed that in vitro measurements using simple crystalloid solutions cannot readily substitute for in vivo measurements of dialyzer function, and permitted a more accurate calculation of each patient's prescribed dialysis dose and urea volume.

Adult↗
PubMedDate not supplied

Improving outcomes in CKD and ESRD patients: carrying the torch from training to practice.

Practicing nephrologists are spending more time caring for end-stage renal disease (ESRD) and chronic kidney disease (CKD) patients. Despite this focus, and considerable advances in the understanding of those aspects of care that impact on clinical outcomes, morbidity, mortality, and quality of life for these patients has not improved substantially over the past decade. One of the possible explanations for this lack of progress is the structure of current nephrology training programs, where ESRD and CKD patient care is not emphasized. To address this issue, we developed a short preceptorship for second-year nephrology fellows, including didactic lectures and workshops. Of 67 participating fellows, 50% were from programs offering 3 or fewer months of exposure to outpatient hemodialysis, and 25% reported no exposure to peritoneal dialysis. Of more concern, 25% reported no "official rounds" with an attending nephrologist on dialysis patients. If nephrologists are to take their appropriate place as leaders of the care delivery team, nephrology fellowships must be restructured with appropriate emphasis placed on the comprehensive care of ESRD and CKD patients.

Attitude of Health Personnel↗
PubMedDate not supplied

Revisiting the hemodialysis dose.

An adequate dose of hemodialysis is currently defined by the Kidney Disease Outcomes Quality Initiative (K/DOQI) and European guidelines as a delivered single-pool urea Kt/V (spKt/V) of 1.2 and 1.4, respectively. Results from several studies, in particular the Hemodialysis (HEMO) study, have largely supported the legitimacy of these guidelines, although they may need to be altered or amended for certain patient subgroups. This review discusses several potential changes to current guidelines based on recent clinical outcome studies. The following questions are addressed: 1) Should the dialysis dose for low molecular weight water-soluble solutes (i.e., urea) be normalized by the body distribution volume for urea? 2) Should spKt/V or equilibrated Kt/V (eKt/V) be used for routine monitoring of the hemodialysis dose? 3) Should the dialysis dose for small solutes be dependent on gender? 4) Should the dialysis dose for middle molecules be used in clinical practice? 5) What should be the dialysis dose when using hemodialysis treatment strategies that are more frequent than thrice weekly?

Dialysis Solutions↗