Improving survival of octogenarian patients selected for haemodialysis

Usha N. Peri1, Andrew Z. Fenves2 and John P. Middleton1,

1 Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas and 2 Baylor Medical Center, Dallas, Texas, USA



   Abstract
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
Background. The incidence of end-stage renal disease (ESRD) among patients over the age of 80 has nearly tripled in the last decade, making the ‘old-old’ the fastest growing ESRD demographic group. Despite this, very little information is available on the characteristics and survival of patients who initiate haemodialysis (HD) after reaching this age.

Methods. We performed a retrospective study on all patients who entered an outpatient HD programme after the age of 80, from January 1988 to September 1998. A total of 106 charts were reviewed from a single nephrology practice group. Eleven patients were excluded due to incomplete data. The survival probability was calculated using the Kaplan–Meier method.

Results. The characteristics of 95 patients were as follows: mean age at initiation of dialysis, 83.7 years; female, 50.5%; Caucasian, 40.0%, African–American, 30.0%; Hispanic, 10.0%; Asian, 4.3%; polytetrafluorethylene grafts, 80.0%; primary fistulas, 5.6%; tunnelled catheters, 5.6%; mean established Kt/V, 1.68; urea reduction ratio (URR), 0.74; estimated dry weight (EDW), 60.3 kg. ESRD was attributed to hypertension in 37%, diabetes in 22% and analgesic use in 8%. The 1-, 2- and 5-year survival probability of the entire group was 82.6±4.0%, 64.0±5.6%, and 19.6±6.0%, respectively. The median survival was 29 months. When comparing survival probability of patients who were in the highest quartiles of URR and EDW to those in the lowest quartile there was no discernible difference. However, the 2-year survival probability of patients initiated after January 1, 1995 (76.9±8.4) was significantly better than those initiated from 1988–1994 (47.8±6.5; P<0.05).

Conclusions. From analysis of this cohort, we conclude that: (i) elderly patients selected for outpatient HD programmes have substantially better survival than previously reported; (ii) Kt/V does not correlate with survival in this demographic group; and (iii) contemporary dialysis practice is associated with better likelihood of survival of elderly patients in outpatient HD programmes.

Keywords: dialysis adequacy; dry weight; elderly; haemodialysis; octogenarians; survival



   Introduction
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
Currently, over 20% of the US population are over 65 years of age and exposed to the risk of declining renal function [13]. Since the prevalence of hypertension and diabetes mellitus in this population is nearly 50% and 25%, respectively, it is not surprising that 40% of incident patients in the US end-stage renal disease (ESRD) programme are over 65 and 22.7% are above 75 years-of-age [1]. Furthermore, the median age of incident ESRD patients in the US was 65 years in 1997 [1]. It was estimated that 60% of all ESRD patients would be above the age of 65 by the year 2000 [2,3]. This has created the most rapidly growing demographic group in the US ESRD population—the ‘old-old’ group of patients over the age of 75 years.

Usually, due to co-morbid conditions or physical debility, an overwhelming majority of old-old patients are placed in outpatient haemodialysis (HD) clinics rather than peritoneal dialysis or home-treatment programmes. The United States Renal Data Survey (USRDS) database indicates that 84.2% of the geriatric patients undergo in-centre HD [4]. Despite this, relatively few studies have been performed to examine the survival of elderly patients in HD programmes. The current practice of initiating elderly patients on contemporary HD programmes in the US has not been extensively evaluated.

This retrospective study was performed in a large cohort of patients in a single nephrology practice to characterize the outcomes of the most rapidly growing demographic group in the US HD patient population.



   Subjects and methods
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
This is a retrospective review of octogenarian patients maintained on chronic HD. A total of 106 patients above the age of 80 were initiated on outpatient HD between January 1988 and September 1998 from a single nephrology group practice (Dallas Nephrology Associates). A total of 20 different dialysis clinics were employed during this time period. Of the initial group, 11 patients were excluded because the chart data were incomplete or the patients had adequate recovery of renal function to be discharged from the HD programme. Outpatient records of the remaining 95 patients were reviewed. The following data were collected from the last monthly computerized dialysis note available for each patient: age at initiation of dialysis; gender; race; duration of dialysis; primary renal diagnosis; number of co-morbid conditions; dialysis adequacy (established Kt/V and urea reduction ratio (URR)); estimated dry weight (EDW); and the type of permanent vascular access. Mean values for Kt/V, URR, and EDW were used when more than one value was available. Causes of death were determined from hospital summaries or death certificates, when available.

Descriptive statistics were derived from the above data. The survival probability was calculated using the Kaplan–Meier method [6]. The survival probability of patients starting dialysis prior to 1995 was compared to that of patients starting dialysis after 1995 using the log-rank method [5]. Data were censured if a patient was transferred to a different dialysis unit. A patient was assumed to have expired if dialysis was terminated by volition. None of the patients included received a renal allograft during this period. The survival probability of patients in the highest and the lowest quartiles of URR and EDW were compared using the Kaplan–Meier and the log-rank methods [5].

Standards of care changed during the period of study. All patients were dialysed for 3.5–4.5 h, three times a week, utilizing a cuprophane membrane until 1989 and then using polysulphone (F 80A, Fresenius Medical Care NA; Lexington, MA) membrane from January 1989 to September 1998. Bicarbonate dialysate was used throughout the study period. Erythropoietin use started in 1991. After 1990 the patients were managed with re-use programmes. The dialysers were re-used with a renalin-based system and the dialyser was considered acceptable if the total fibre bundle volume was greater than 80% of the original volume. Erythropoietin was first used in this population in 1991. Over the last 7 years of the observation period, increasing numbers of patients were treated with erythropoietin. At the end of the study period, 85–90% of patients were receiving intermittent erythropoietin. Kt/V and URR were calculated from pre- and post-treatment BUN samples, the post-treatment sample was drawn 15–30 s after the end of treatment, and Kt/V was calculated assuming single pool kinetics.



   Results
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
Ninety-five patients aged 80 or above entered an outpatient HD programme between January 1988 and September 1998. The mean age of the group at the time of initiation was 83.7 years, and most were Caucasian (Table 1Go). End-stage renal disease was attributed to hypertension in nearly half of the cases. The majority of these patients had polytetrafluorethylene )PTFE( grafts in place for access. Compared to the USRDS mean URR of 68.2% in 1998, the delivered dose of HD was high in the cohort, estimated by a mean Kt/V of 1.70 and mean URR of 74% [4]. The average number of recorded co-morbid conditions was 3.1. The most common co-morbid conditions were coronary artery disease, congestive heart failure, peripheral vascular disease (with or without amputations) and atrial fibrillation (Table 2Go). The survival probability was calculated for the study population using the Kaplan–Meier method (Figure 1Go). The median survival for this group of patients was 29 months. The 1-, 2-, and 5-year survival probability was 82.6±4%, 64±5.6%, and 19.6±6.0% respectively. When compared to survival of similar patients (aged 80 and above) from USRDS, the survival probability of our patient population was substantially better (Table 3Go).


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Table 1. Characteristics of cohort (n=95)

 

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Table 2. Co-morbid conditions and medications of elderly patients on haemodialysis

 


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Fig. 1. Kaplan–Meier survival probability for entire cohort of patients started on haemodialysis after the age of 80.

 

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Table 3. Survival of octogenarians on haemodialysis

 
During the study follow up period, 59 patients expired. We could determine precise causes of death from records obtained from 30 cases. The causes included: cardiovascular (40%); discontinuation of dialysis (20%); sepsis (13.3%); malignancy (13.3%); stroke (10%); and gastrointestinal bleed (3.3%).

When survival was determined based on date of initiation, we found that patients initiated after 1995 had significantly higher survival than those initiated before 1995 (Figure 2Go). For patients initiated after January 1, 1995, the 2-year survival probability was 76.9±8.4 compared to patients who entered treatment from 1988 to 1994 (47.8±6.5). Because survival of HD patients has been correlated to body size and to adequacy of urea clearance, we compared outcomes of elderly patients based on URR and EDW. There was no discernible difference in the survival probability of patients in the highest quartile for URR and EDW compared to those in the lowest quartile (Figure 3Go).



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Fig. 2. Kaplan–Meier survival probability of elderly patients initiated before (dashed line) and after January 1, 1995 (P<0.005).

 


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Fig. 3. Effect of urea reduction ratio (URR) and estimated dry weight (EDW) on survival of elderly patients on haemodialysis. (A) Kaplan–Meier survival probability of patients with EDW greater than 68 kg (dashed line) compared to those less than 50 kg. (B) Survival of patients dialysed with URR less than 0.70 compared to those greater than or equal to 0.78 (dashed line).

 



   Discussion
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
The population profiles of industrialized nations are becoming increasingly weighted toward older demographic groups. In the US, this contributes to the trend of initiating greater numbers of elderly patients into HD programmes. The USRDS database suggests that the number of incident patients above the age of 75 has grown by more than 8% over the last 5 years [1]. However, elderly patients on HD are a heterogeneous group of patients, and their chronological age may not necessarily correlate with biological age. There is a considerable amount of information available on renal replacement therapy in elderly patients older than 65 years [3,17,18]. However, there is very little information available on patients over 80 years of age. This study evaluates the patient characteristics and survival in a large cohort of octogenarians managed in a US contemporary HD programme.

The mean age at initiation in our cohort was 83.7 years. The absence of male predominance in this age group is a reflection of the survival advantage of females and is consistent with that previously reported [7,9]. The predominance of Caucasian patients may be a reflection of the local patient pool and is a unique property of this group. This feature could influence survival, since most observations suggest that Caucasian patients have a worse survival rate than African–Americans on HD [7]. Similar to cross-sectional studies and data surveys in the US, the majority of the patients in the old-old cohort required PTFE grafts for vascular access. The elderly patients have a higher rate of synthetic grafts as opposed to primary fistulas due to advanced vascular disease [17]. It is also important to note that the incidence of tunnelled catheters was low and was predominantly used for the group who were undecided about long-term dialysis and were on a ‘trial’ of HD.

Renal disease was attributed to hypertensive nephrosclerosis in nearly half of the patients, diabetic glomerulosclerosis in nearly a quarter, and chronic GN, analgesic nephropathy, and other disorders accounted for the remaining cases of ESRD. These proportions are similar to descriptions of the overall aged US ESRD population, but they differ from published observations that renal vascular disease is the leading cause of ESRD [7,17]. The predominance of hypertension as an ESRD aetiology may reflect a survival advantage compared to other illnesses. In contrast, diabetes is the most common cause of ESRD in the US [1]. Patients in our elderly cohort average 3–4 co-morbid conditions (not including diabetes), and these most commonly include cardiovascular, peripheral vascular and gastrointestinal diseases [7,9]. Of significance is the high number of malignancies in this group (Table 2Go).

The probability of survival in our group was substantially better than a similar group of patients from the USRDS database [1]. This is especially significant as the survival data from USRDS excludes the first 90 days when the mortality rate may be expected to be high. The median survival of patients in this group of patients was 29 months. Considering that the life expectancy for octogenarians without ESRD is 5.1 to 8.9 years depending on race and gender, a median survival of nearly 2.5 years is particularly surprising [6]. This suggests that outpatient HD can add valuable months or even years to the life of an octogenarian. Among the limited number of studies published on the survival of octogenarians on HD, our series is the largest (Table 3Go). The median survival, 1-year survival and 2-year survival were all substantially better in the present series than in comparable series.

Dialysis techniques and supportive medical therapies continue to improve each year. While mortality rates among ESRD patients remain unacceptably high, the survival for many demographic groups is improving [6]. We compared the survival probability of patients who initiated prior to 1995 with that of patients who initiated post-1995 to see if there was a significant difference. The 1-year and 2-year survival probability before 1995 was 73.8±6.1% and 47.8±6.5% respectively as compared to 84.2±5.3% and 76.9±8.4% after 1995, which was considerably better. Interestingly, these results occurred despite more liberal assignment of elderly patients to HD programmes.

In addition to duration of life, it is equally important that the quality of life improves with HD. It is well established that ESRD patients have a lower objective quality of life compared to the normal population. However, it is intriguing that the same group of patients had comparable scores of subjective quality of life to the normal population [21,23]. This suggests that ESRD patients perceived life to be satisfactory. It is also interesting to note that some authors have reported that the overall life satisfaction of the older patients was better when compared to their younger counterparts, despite increasing co-morbidity and declining physical function [24]. Although we have no data on this issue, the fact that patients continued on HD when the option of stopping therapy was available supports the view that their perceived quality of life was acceptable.

Survival of patients placed in an outpatient HD programme is influenced by several factors [14,15,18]. Advancing age has been shown to be a risk factor for mortality in several large database cross-sectional analyses [19]. However, when the effects of co-morbidity (diabetes mellitus, peripheral vascular disease, or ischaemic heart disease) were taken into consideration, a significant positive correlation with mortality was found irrespective of the age of the patients [25]. Hence some of the effects of advanced age may be secondary to co-morbidity. In this context the low reported co-morbidities in our series may have contributed to the higher survival.

Diabetes is clearly a major mortality risk. The low rate of diabetes in our patients may have contributed to the high survival of this group. The nutritional status of an individual as measured by albumin, predialysis creatinine, phosphorus and potassium and more recently the estimated dry weight have all been shown to be very important markers of mortality [14,13,18]. Several observations suggest that poor clearance of urea on HD, estimated by URR <65–70% or Kt/V<1.2–1.3, confers a higher mortality risk [14,15]. However, recent reports from Lowrie et al. [13] demonstrate that patients with higher body weight to height ratio have better survival despite low URR. Similarly Owen et al. [12] demonstrated that the positive correlation between URR and survival might not be sustained in black men. This discrepancy in URR and survival was felt to be secondary to inclusion of a nutritional parameter (volume of distribution of urea) in the calculation of dose of dialysis. Supporting this hypothesis Chertow et al. [16] showed that the reverse ‘j-shaped’ relationship between URR and survival can be eliminated by measuring dialysis dose using Kt instead of URR. We compared the survival probability of patients in the highest quartiles of URR and found no significant difference. This may be another demographic group where there is poor correlation between measures of urea clearance and patient survival. Similarly, no difference in the survival was found between the highest and lowest quartile of body weight.

This retrospective study has some limitations. The predominant limitation is that the old-old cohort on dialysis was probably a select group. For example, we were unable to determine how many elderly patients chose to or were advised not to receive dialysis therapy. Therefore, it is likely that the survival in this cohort does not correspond to all elderly patients with renal failure. It is interesting to note, however, that the number of incident patients in the US ESRD population over the age of 80 has increased by more than 80%, while the same group in the overall population has increased by only 14% [4]. The optimum treatment for this group will become an even greater question in the next decade.

In conclusion, we demonstrate that the survival probability of octogenarians in outpatient HD can be much better than previously reported. The survival also appears to be improving with contemporary practice habits. Conventional markers of prognosis for survival on HD may not pertain to this important and rapidly growing demographic group.



   Acknowledgments
 
The authors are indebted to Kathy Hart and Kimberly Jones for their help in preparing this manuscript.



   Notes
 
Correspondence and offprint requests to: Dr John P. Middleton, Division of Nephrology, Department of Internal Medicine, UT Southwestern Medical Center, 5323 Harry Hines Blvd, H5.112, Dallas, TX 75390–8856, USA. Email: john.middleton{at}utsouthwestern.edu Back



   References
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 

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Received for publication: 20. 6.00
Revision received 11. 6.01.