Wendy E. Bloembergen

Predialysis blood pressure and mortality risk in a national sample of maintenance hemodialysis patients

The role of predialysis blood pressure (BP) as a risk factor for the high mortality in chronic hemodialysis (HD) patients has remained controversial. The objective of the current study was to further explore in a national random sample of 4,499 US hemodialysis patients any relationship of systolic or diastolic and predialysis or postdialysis BP with mortality, while considering subgroups of patients and controlling for other patient characteristics and comorbidities. The main finding of this study is the association of a low predialysis systolic BP with an elevated adjusted mortality risk (relative mortality risk [RR] = 1.86 for systolic BP < 110, P < 0.0001). No association with an elevated mortality risk could be observed for predialysis systolic hypertension (RR = 0.98 to 0.99, not significant [NS]), except for an elevated risk of cerebrovascular deaths. Postdialysis systolic BP was associated with an elevated mortality risk both for low and high BP levels as compared with midrange BP. Further evaluation of the elevated mortality risk associated with low predialysis systolic BP indicated similar patterns for both diabetic and nondiabetic subgroups and for patients with and without congestive heart failure (CHF) or coronary artery disease, although it was more pronounced among those with CHF. The level of predialysis fluid excess did not modify these results substantially. The findings from this historical prospective national study do not argue against the treatment of hypertension and suggest greater attention to postdialysis hypertension. The strikingly elevated mortality risk with low predialysis systolic BP suggests that low predialysis BP needs to be viewed with great concern and avoided where possible.

Relationship of dialysis membrane and cause-specific mortality

A number of studies have suggested that type of dialysis membrane is associated with differences in long-term outcome of patients undergoing hemodialysis, both in terms of morbidity and mortality. The purpose of this study was to determine the relationship of membrane type and specific causes of death. Data from the United States Renal Data System Case Mix Adequacy Study, a national random sample of hemodialysis patients who were alive on December 31, 1990, were used. Our study was limited to patients in this data set who were undergoing dialysis for at least 1 year (n = 4,055). For the main analytic models, membrane type was classified into two categories: unmodified cellulose or MC/SYN (which combines modified cellulose [MC] and synthetic membranes [SYN]). The relationships of membrane type and major causes of mortality were analyzed using Cox proportional hazards models, which adjusted for multiple (21) covariates, including demographics, comorbidity, Kt/V, and other parameters. Patients were censored at transplantation or 60 days after a switch to peritoneal dialysis. Compared with patients dialyzed with unmodified cellulose membranes, the adjusted relative mortality risk (RR) from infection was 31% lower (RR = 0.69; P = 0.03) and from coronary artery disease was 26% lower (RR = 0.74; P = 0.07) for patients dialyzed with MC/SYN membranes. No statistically significant difference (all P > 0.1) was found in mortality risk from cerebrovascular disease (RR = 1.08), other cardiac causes (RR = 0.86), malignancy (RR = 0.90), or other known causes (RR = 0.82) between patients dialyzed with MC/SYN compared with unmodified cellulose membranes. These results offer support to reported experimental and observational clinical studies that have found that unmodified cellulose membranes may increase the risk for both infection and atherogenesis. Further studies are necessary to evaluate the possibility of confounding factors, compare more specific membrane types, and determine the pathophysiology linking membrane type to cause-specific mortality.

Epidemiogical Persperspective on Infections in Chronic Dialysis Patients

Infectious complications are a source of substantial morbidity and a common cause of death among dialysis patients. This article considers the magnitude and impact of the problem of infection among patients treated with hemodialysis (HD) and peritoneal dialysis (PD) using data from national registries and large cohort studies of patients with end-stage renal disease (ESRD). United States Renal Data System (USRDS) data indicate that in the United States for years 1991 to 1992, infection accounted for 12% of all deaths among HD patients and 15% of all deaths among PD patients. Septicemia was the underlying cause in 76% of these infectious deaths among HD patients, of which the vascular access, peritonitis, peripheral vascular disease, and other causes accounted for 12%, 5%, 24%, and 59% respectively. Among PD patients, septicemia accounted for 79% of infectious deaths. Of these deaths attributable to septicemia, peritonitis, peripheral vascular disease, and other causes were reported as the cause in 35%, 23%, and 41 % respectively. Infection is also a major cause of morbidity in the dialysis population. Among HD patients, an average of 7.6 bacteremic episodes per 100 patient years (0.076 per year) has been described, of which 48% were associated with access infections. Among PD patients, studies have reported peritonitis rates ranging from 1 in 7.6 to 21.5 months (0.56 to 1.58 per patient year) and exit and/or tunnel infections occurring at a rate of 0.6 episodes per year. The known predictors of infectious complications among these populations are reviewed.

Association of gender and access to cadaveric renal transplantation

Previous studies have revealed that females are less likely than males to receive a renal transplant, the most successful form of treatment of end-stage renal disease (ESRD). The purpose of this study was to determine whether the barrier is to inclusion on the transplant waiting list or to transplantation after being placed on the transplant waiting list. An existing data set was used that included data from the Michigan Kidney Registry, supplemented with data received from the Organ Procurement Agency of Michigan. White and black patients less than 65 years of age and starting ESRD treatment between January 1, 1984, and December 31, 1989, were included. Cox proportional hazards models were used to determine the effect of gender on (1) time to transplantation among all ESRD patients, (2) time from diagnosis of ESRD to inclusion on the transplant waiting list among all ESRD patients, and (3) time from inclusion on the waiting list to transplantation among those patients on the waiting list. Patients were censored at the time of living-related transplantation or death, and were monitored until December 31, 1989. In all, 5,026 incident ESRD patients were included in the study (44.3% female). Of these, 1,626 patients were included on the waiting list (40.1% female); 823 of these received a transplant (37.7% female). Adjusting for age, race, and diagnosis, females were 25% less likely to receive a cadaveric transplant than males (female to male relative rate ratio [RR], 0.75; P < 0.001). Females with ESRD aged 46 to 55 years and 56 to 65 years were 33% (RR, 0.67; P < 0.001) and 29% (RR, 0.71; P < 0.05) less likely to be included on the transplant waiting list, respectively, than their male counterparts. There was no difference in the rate of wait list inclusion among ESRD patients younger than 46 years. Females with ESRD who were included on the transplant waiting list were 26% (RR, 0.74; P < 0.001) less likely to receive a transplant than males on the waiting list. These results indicate that females are both less likely to be on the transplant waiting list (ages over 45 years) and, once on the list, less likely to receive a transplant (all ages) than males. Further study is necessary to determine the factors contributing to these important barriers to transplantation among females with ESRD.

Cardiac Disease in Chronic Uremia: Epidemiology

Cardiac abnormalities develop during chronic renal failure. The prevalence of ischemic heart disease, cardiac failure, and left ventricular disorders is high among patients initiating end-stage renal disease (ESRD) therapy, and appears to be getting higher. Age, gender, race, diabetes, and possibly geographic location are predictive of the presence of several cardiac conditions. Cardiac morbidity after the initiation of ESRD therapy is high, and cardiac causes are the most common reported cause of death. Cardiac abnormalities present on starting dialysis contribute to this morbidity and mortality. In epidemiological studies, higher cardiac death rates have also been associated with dialysis rather than transplantation as mode of ESRD therapy, peritoneal rather than hemodialysis, lower dose of dialysis, and unmodified cellulose rather than modified cellulose/synthetic hemodialysis membranes.

Outcomes of CAPD versus hemodialysis in the elderly

Over the past decade, the incidence of treated end-stage renal disease (ESRD) has increased rapidly in the U.S. [1] and in many other countries [2–6]. This rise has been greatest among the elderly (Figs. 1 and 2), who now have the highest incidence of ESRD. In the U.S., the median age of the overall ESRD population has increased from 55 years in 1980 to 61 years in 1990.