Adequacy Targets of Peritoneal Dialysis in the Asian Population

End-stage renal disease affects a large number of patients in Asia. The percentage of patients utilizing PD varies significantly in Asian countries. Continuous ambulatory peritoneal dialysis (CAPD) accounts for about 80% of the dialysis population in Hong Kong.

In this review, we address several questions related to adequacy targets in Asians: Are Asians different? Is dialysis adequacy important for Asians? What is the magnitude of the benefit and the optimal dose of dialysis prescription? Is the adequacy target realistic?

The current international recommendations, including the Dialysis Outcomes Quality Initiative guidelines, are compared with some of our own data for Asian patients. Our published data on dialysis adequacy, nutrition, residual renal function, and peritoneal membrane transport showed that those factors have a significant impact on the morbidity and mortality of PD patients in Hong Kong.

Our results show that solute clearance as measured by Kt/V has a significant impact on the outcome of Asian CAPD patients. Although Chinese PD patients have excellent medium-term patient and technique survival despite an apparently lower Kt/V as compared with the CANUSA standard, that favorable outcome should not prevent nephrologists from providing adequate dialysis to Asian patients. From our own data and analysis, we propose a target Kt/V of 1.9 in Asian CAPD populations. Small-volume dialysis (6 L daily) may be an acceptable compromise in some Asian populations with a smaller body size, especially with residual renal function, given the financial constraints in some developing countries.

Dialysis adequacy means more than a Kt/V value; other clinical parameters are equally if not more important. Thus we should also aim at achieving adequate fluid removal and volume homeostasis, blood pressure control, good nutrition, normal acid–base balance, normal mineral metabolism, minimal anemia, and normal lipid metabolism.

Is Obesity a Favorable Prognostic Factor in Peritoneal Dialysis Patients?

Objective

To determine the influence of an elevated body mass index (BMI) on cardiovascular outcomes and survival in peritoneal dialysis (PD) patients.

Design

Prospective, observational study of a prevalent PD cohort at a single center.

Setting

Tertiary care institutional dialysis center.

Patients

The study included all patients with a BMI of at least 20 who had been receiving PD for at least 1 month as of 31 January 1996 ( n = 43). Patients were classified as overweight [BMI > 27.5; mean ± standard error of mean (SEM): 32.1 ± 1.1; n = 14] or normal weight (BMI 20 – 27.5; mean ± SEM: 23.8 ± 0.4; n = 29).

Outcome Measures

Patient survival and adverse cardiovascular events (myocardial infarction, congestive cardiac failure, cerebrovascular accident, and symptomatic peripheral vascular disease) were recorded over a 3-year period.

Results

At baseline, no significant differences were seen between the groups in clinical, biochemical, nutritional, or echocardiographic parameters, except for a lower dietary protein intake (0.97 ± 0.10 g/kg/day vs 1.44 ± 0.10 g/ kg/day, p = 0.004) and a higher proportion of well-nourished patients by subjective global assessment (100% vs 72%, p < 0.05) in the overweight group. After 3 years of follow-up, 29% of overweight patients and 69% of normal-weight patients had died ( p < 0.05). Using a Cox proportional hazards model, a BMI greater than 27.5 was shown to be an independent positive predictor of patient survival, with an adjusted hazard ratio (HR) of 0.09 [95% confidence interval (CI): 0.01 – 0.85; p < 0.05]. However, being overweight did not significantly influence myocardial infarction-free survival (adjusted HR: 0.33; 95% CI: 0.07 – 1.48; p = 0.15) or combined adverse cardiovascular event-free survival (adjusted HR: 0.67; 95% CI: 0.23 – 1.93; p = 0.46).

Conclusions

Obesity conferred a significant survival advantage in our PD population. Obese patients should therefore not be discouraged from receiving PD purely on the basis of BMI. Moreover, maintaining a higher-than-average BMI to preserve “nutritional reserve” may help to reduce the mortality and morbidity rates associated with PD.

Nutrition Indices in Obese Continuous Peritoneal Dialysis Patients with Inadequate and Adequate Urea Clearance

♦ Objective

To test whether better nutrition is associated more with adequate urea clearance than with inadequate urea clearance in obese patients on continuous peritoneal dialysis (CPD).

♦ Design

Retrospective analysis of clearance and nutrition indices in obese CPD patients. Only obese patients were analyzed. Obesity was defined as a ratio of actual weight to desired weight (W/DW) ≥ 1.2. The dose of dialysis was considered adequate at weekly Kt/V urea ≥ 2.0. Small solute clearances and nutrition indices were compared between patients with weekly Kt/V urea < 2.0 and patients with weekly Kt/V urea ≥ 2.0 at the first clearance study.

♦ Setting

Four university-affiliated and two private dialysis units in Canada and the United States.

♦ Patients

A total of 270 CPD patients with W/DW ≥ 1.2 at the first clearance study.

♦ Results

Among the 270 obese CPD patients, 157 (58.1%) were underdialyzed (weekly Kt/V urea 1.66 ± 0.22) and 113 (41.9%) had adequate dialysis (weekly Kt/V urea 2.51 ± 0.47) at the first clearance study. Creatinine clearance values also differed between the underdialyzed and adequately dialyzed obese groups (55.6 ± 15.2 vs 87.6 ± 29.8 L/1.73 m2 weekly, respectively, p < 0.001). The underdialyzed group contained fewer women (39.5% vs 60.2%, p < 0.001) and more patients with anuria (35.0% vs 8.8%, p < 0.001), and had higher serum urea (20.7 ± 6.9 vs 18.2 ± 5.3 mmol/L, p = 0.001) and serum creatinine (974 ± 283 vs 734 ± 275 μmol/L, p < 0.001), marginally lower serum albumin (35.8 ± 5.2 vs 37.2 ± 6.4 g/L, p = 0.082), lower urea nitrogen excretion (5778 ± 2290 vs 7085 ± 2238 mg/24 hr, p < 0.001) and indices derived from urea nitrogen excretion (protein nitrogen appearance and normalized protein nitrogen appearance), and lower creatinine excretion (1034 ± 349 vs 1217 ± 432 mg/24 hr, p < 0.001) and indices derived from creatinine excretion (lean body mass normalized to actual or desired weight) than the adequately dialyzed group.

♦ Conclusion

Nutrition indices derived from urea nitrogen and creatinine excretion are worse in underdialyzed than in adequately dialyzed obese CPD patients. This finding may have clinical importance, despite the mathematical coupling between small solute clearances and excretion rates in cross-sectional studies, because of evidence from other studies that small solute excretion rate in cross-sectional studies is a robust independent predictor of outcome in CPD.

Increasing the Dialysis Volume and Frequency in a Fixed Period of Time in CPD Patients: The Effect on Kpt/V and Creatinine Clearance

Background

The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (K/DOQI) has evidence- and opinion-based recommendations for weekly Kt/Vurea and weekly total creatinine clearance (CC) in chronic peritoneal dialysis (CPD) patients. Using standard continuous ambulatory peritoneal dialysis technique, it is often difficult to achieve the suggested targets in anuric patients with large body mass. Thus, the use of automated peritoneal dialysis (APD) has been increasingly utilized to achieve adequate clearances. Automated dialysis is usually performed at night over an 8- to 10-hour period. The role of increases in dialysate volume and frequency of exchanges during this time period to achieve these target K/DOQI recommendations remains uncertain. We decided to study the effects of increasing the volume and number of exchanges in a fixed period of time in CPD patients.

Methods

In the New Haven CAPD unit, 29 patients maintained on APD were considered eligible for the study and 11 agreed to participate. The patients were characterized according to standard peritoneal equilibration test criteria. The patients were placed into two groups: group 1 included high (H) and high-average (HA), and group 2 low-average (LA) transporters. The patients were dialyzed at night for 9 hours with standard cycling technique, using 2.5% Dianeal (Baxter Healthcare, Deerfield, Illinois, USA) solution, with a cycle volume of 2500 mL, and a 2000-mL daytime dwell. Three studies were done on each patient using a total dialysis volume of 9.5 L (3 cycles), 14.5 L (5 cycles), and 19.5 L (7 cycles). Daily Kpt/Vurea and daily CCp (peritoneal) (L/day/1.73 m2) were obtained.

Results

Six patients were H or HA (group 1) and 5 were LA transporters (group 2). For the group 1 patients, mean weight was 86.6 ± 13.5 kg; Kpt/Vurea was 1.68 ± 0.21 using 9.5 L, 2.03 ± 0.28 for 14.5 L ( p < 0.05 compared to 10 L), and 2.28 ± 0.28 with 19.5 L ( p < 0.05 compared to 10 L and 15 L); mean weekly CCp was 45.43 ± 7.63 L/1.73 m2 for 9.5 L ( p < 0.05 compared to 14.5 L and 19.5 L), 51.17 ± 7.07 with 14.5 L, and 54.67 ± 10.08 for 19.5 L; ultrafiltration rates were not different in the three studies. For the group 2 patients, mean weight was 74.3 ± 17.7 kg; mean weekly Kpt/Vurea was 1.68 ± 0.35 using 9.5 L, 2.10 ± 0.42 for 14.5 L ( p < 0.05 compared to 9.5 L), and 2.31 ± 0.56 for 19.5 L ( p < 0.05 compared to 9.5 L and 14.5 L); mean weekly CCp was 42.56 ± 10.64 L/1.73 m2 for 9.5 L ( p < 0.05 compared to 14.5 L and 19.5 L), 50.89 ± 12.66 for 14.5 L, and 51.94 ± 11.20 for 19.5 L; ultrafiltration was lower in the 9.5-L study than in the 14.5-L and 19.5-L studies, but was not different in the 14.5-L and 19.5-L studies.

Conclusions

In both H/HA and LA transporters, Kpt/Vurea and CCp rise significantly when the frequency of exchanges and total volume of dialysate are increased. Thus, the use of larger volumes of dialysate with cycling peritoneal dialysis may result in increased clearances of urea and creatinine.

Obesity is a Risk Factor for Peritonitis in the Australian and New Zealand Peritoneal Dialysis Patient Populations

Objective

The aim of the present investigation was to examine the association between body mass index (BMI) and peritonitis rates among incident peritoneal dialysis (PD) patients in a large cohort with long-term follow-up.

Design

Retrospective observational cohort study of the Australian and New Zealand PD patient population.

Setting

Australia and New Zealand Dialysis and Transplant (ANZDATA) Registry.

Participants

The study included all incident adult patients ( n = 10 709) who received PD in Australia and New Zealand in the 12-year period between 1 April 1991 and 31 March 2003. Patients were classified as obese (BMI ≥ 30 kg/m2), overweight (BMI 25.0 – 29.9 kg/m2), normal weight (20 – 24.9 kg/m2), or underweight (< 20 kg/m2).

Main Measurements

Time to first peritonitis and episodes of peritonitis per patient-year were recorded over the 12-year period.

Results

Higher BMI was associated with a shorter time to first peritonitis episode, independent of other risk factors [hazard ratio 1.08 for each 5-kg/m2increase in BMI, 95% confidence interval (CI) 1.04 – 1.12, p < 0.001]. When peritonitis outcomes were analyzed as episodes of peritonitis per patient-year, these rates were significantly higher among patients with higher BMI: underweight 0.69 episodes/year (95% CI 0.66 – 0.73), normal weight 0.79 (95% CI 0.77 – 0.81), overweight 0.88 (95% CI 0.85 – 0.90), obese 1.06 (95% CI 1.02 – 1.09). Coronary artery disease and chronic lung disease were associated with both shorter time to first peritonitis and higher peritonitis rates, independently of these other factors. There was also a “vintage effect,” with lower peritonitis rates seen among people who commenced dialysis in more recent years.

Conclusions

Higher BMI at the commencement of renal replacement therapy is a significant risk factor for peritonitis. The mechanisms for this remain undefined.

Obesity Is Associated with Worse Peritoneal Dialysis Outcomes in the Australia and New Zealand Patient Populations

ABSTRACT. Although obesity is associated with increased risks of morbidity and death in the general population, a number of studies of patients undergoing hemodialysis have demonstrated that increasing body mass index (BMI) is correlated with decreased mortality risk. Whether this association holds true among patients treated with peritoneal dialysis (PD) has been less well studied. The aim of this investigation was to examine the association between BMI and outcomes among new PD patients in a large cohort, with long-term follow-up monitoring. Using data from the Australia and New Zealand Dialysis and Transplant Registry, an analysis of all new adult patients (n= 9679) who underwent an episode of PD treatment in Australia or New Zealand between April 1, 1991, and March 31, 2002, was performed. Patients were classified as obese (BMI of ≥30 kg/m2), overweight (BMI of 25.0 to 29.9 kg/m2), normal weight (BMI of 20 to 24.9 kg/m2), or underweight (BMI of <20 kg/m2). In multivariate analyses, obesity was independently associated with death during PD treatment (hazard ratio, 1.36; 95% confidence interval, 1.14 to 1.54;P< 0.05) and technique failure (hazard ratio, 1.17; 95% confidence interval, 1.07 to 1.26;P< 0.01), except among patients of New Zealand Maori/Pacific Islander origin, for whom there was no significant relationship between BMI and death during PD treatment. A supplementary fractional polynomial analysis modeled BMI as a continuous predictor and indicated a J-shaped relationship between BMI and patient mortality rates and a steady increase in death-censored technique failure rates up to a BMI of 40 kg/m2; the mortality risk was lowest for BMI values of approximately 20 kg/m2. In conclusion, obesity at the commencement of renal replacement therapy is a significant risk factor for death and technique failure. Such patients should be closely monitored during PD and should be considered for early transfer to an alternative renal replacement therapy if difficulties are experienced. E-mail: stephenm@ anzdata.org.au

Feasibility of adequate solute clearance in obese patients on peritoneal dialysis: a cross-sectional study

BACKGROUND

It is widely assumed that obese patients are poorly suited for peritoneal dialysis (PD). Mathematical models predicting weight limits to achieve adequate solute clearance in anuric patients on continuous ambulatory PD therapy do not apply to the majority of obese patients on PD therapy.

METHODS

To define the extent to which obesity or large body size interferes with successful PD, the feasibility of achieving adequate solute clearance, defined by the Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines, was studied. We reviewed prospectively recorded data for 25 obese patients (body mass index > or = 29) from a group of 58 prevalent PD patients treated in an inner-city ambulatory dialysis center. Adequacy of solute clearances was assessed by comparing weekly Kt/V and weekly creatinine clearance (WCC) with those recommended by the K/DOQI. Adequacy also was examined separately for large patients, defined as those with total-body water (TBW) by the Watson and Watson equation of 48 L or greater. Similar analyses were performed separately for 10 anuric obese patients.

RESULTS

Eighty four percent and 88% of the 25 obese patients achieved K/DOQI targets for weekly Kt/V and WCC, respectively. Among the 10 anuric obese patients, 90% and 70% achieved these targets. Only 60% of those with TBW of 48 L or greater met the Kt/V target.

CONCLUSION

PD remains a viable option for obese patients with end-stage renal disease. It is possible for the majority of obese patients on PD therapy to achieve solute clearances recommended by the K/DOQI.

Progressive Increases in Peritoneal Dialysis Prescription: Patient Acceptance and Complication Rates

Peritoneal dialysis adequacy has an impact on patient mortality. Both the CANUSA study and DOQI Guidelines outline targets for adequacy, and it has been suggested that quantitative adequacy determinations be made at regular intervals. Some groups believe these targets are not achievable because of lack of patient acceptance and high complication rate. We examined the outcome of peritoneal dialysis in a setting where prescription changes are made on clinical grounds, and determined the complication rates and patient acceptance of prescription changes. A total of 154 patients commencing peritoneal dialysis from January 1, 1994,-December 31, 1996, were studied to determine reasons for dialysis prescription changes, patient acceptance of, and complications related to these changes. Point prevalence data for dialysis prescription for our center and other Canadian centers were obtained from the Canadian Institute for Health Information. Co-morbidity - adjusted patient and technique survival for our center versus other centers in Canada was performed by Poisson regression analysis. Dialysis prescription changes were based on clinical assessment. A total of 102 patients started on either > 8 L of dialysate or had an increase in dialysis prescription during the study period. These patients were heavier, on peritoneal dialysis for longer, and fewer were transplanted compared with the patients on standard prescription (8 L or less). Only 4% of patients refused the change in dialysis prescription, and only 13 peritoneal leaks occurred, resulting in 3 transfers to hemodialysis. Our center prescribed a larger number of exchanges than other Canadian centers in 1995-1997. Adjusted mortality rate ratios for our center versus the other Canadian Centers (1990-1996) are equal. The 3 year technique survival for peritoneal dialysis patients from our center between 1990-1996 was 75% vs. 61% for other centers in Canada. At last follow-up, > 60% of patients had a Kt/V urea >2.1 and 45% had a creatinine clearance > 70 L/1.73 m2/week. This Regional Program has successfully prescribed high volume and frequency peritoneal dialysis on clinical grounds alone. This practice is associated with high patient acceptance, equivalent mortality, and higher technique survival compared with the rest of Canada.

Hybrid dialysis: recirculation peritoneal dialysis revisited

In a crossover trial, eight patients were studied during one treatment each of automated peritoneal dialysis (APD) and hybrid dialysis (HyD). During HyD, a fixed quantity of peritoneal dialysis fluid (PDF) was continuously removed at a flow rate of 141.3 +/- 23. 7 mL/min, dialyzed against the secondary dialysate (250 +/- 53.5 mL/min) generated by the hemodialysis delivery system with single-needle dialysis capability, and the regenerated PDF (PDF(HyD)) was reinfused into the peritoneal cavity. Despite using a smaller volume (6,195 +/- 737 versus 13,321 +/- 1,201 mL; P < 0. 0001) of PDF(HyD) with a lower glucose concentration (729 +/- 562 versus 1,659 +/- 373 mg/dL; P < 0.0001) and osmolality (331 +/- 79 versus 387 +/- 184 mOsm/kg; P < 0.001) during HyD compared with APD (PDF(APD)), weight loss was similar with both treatments (1.4 +/- 1. 0 versus 1.6 +/- 1.2 kg). Lactate levels were lower (3.2 +/- 2.5 versus 11.4 +/- 5.4 mEq/L), but pH (7.5 +/- 1.3 versus 5.6 +/- 0.9; P < 0.001) and bicarbonate concentration (22.6 +/- 8.0 versus 11.9 +/- 7.9 mEq/L; P < 0.0001) were greater in PDF(HyD) than PDF(APD). Although the mean dialysate calcium level was lower (6.0 +/- 0.5 versus 6.9 +/- 1.1 mg/dL; P < 0.001) in PDF(HyD), it was more stable throughout the dialysis compared with PDF(APD). A steeper concentration gradient between the blood and dialysate resulted in greater clearance of urea (26.5 +/- 9.1 versus 11.0 +/- 4.7 mL/min; P = 0.04), creatinine (24.1 +/- 11.4 versus 12.0 +/- 7.9 mL/min; P = 0.03), phosphate (19.2 +/- 4.3 versus 9.8 +/- 7.2 mL/min; P = 0.01), and uric acid (15.6 +/- 6.9 versus 9.1 +/- 2.7 mL/min; P = 0.04) and a greater percentage of reduction in values for blood urea nitrogen (20.7% +/- 7.7% versus 11.6% +/- 5.5%; P = 0.02), serum creatinine (16.1% +/- 5.3% versus 6.6% +/- 3.0%; P < 0.001), phosphate (22.7% +/- 8.9% versus 9.8% +/- 4.5%; P = 0.004), and uric acid (15.8% +/- 2.9% versus 6.3% +/- 3.4%; P < 0.001) during HyD than APD. To conclude, HyD is a novel dialytic technique that uses biocompatible bicarbonate-based dialysate to achieve excellent clearance of uremic toxins and ultrafiltration with minimal glucose load.

Influence of convection on small molecule clearances in online hemodiafiltration

BACKGROUND

Dialysis efficacy is mostly influenced by dialyzer clearance. Urea clearance may be estimated in vitro by total ion clearance, which can be obtained by conductivity measurements. We have previously used this approach to assess in vitro clearances in a system mimicking predilutional and postdilutional online hemodiafiltration with a wide range of QD, QB, and ultrafiltration rates. Our current study elaborates on a formula that allows the prediction of the influence of ultrafiltration on small molecule clearances, and validates the mathematical approach both experimentally in vitro and clinically in vivo data.

METHODS

Two conductivimeters in the dialysate side of an E-2008 Fresenius machine were used. HF80 and HF40 polysulfone dialyzers were used; reverse osmosis water and dialysate were used for blood and dialysate compartments, respectively. Study conditions included QB of 300 and 400 mL/min and QD of 500 and 590 mL/min, with a range of ultrafiltration rate from 0 to 400 mL/min in postdilutional hemodiafiltration and to 590 mL/min in predilutional hemodiafiltration. Urea clearances were determined in the in vivo studies, which included 0, 50, 100, and 150 mL/min ultrafiltration rates.

RESULTS

The ultrafiltration rate and clearance were significantly correlated (R > 0.9, P < 0.001) and fitted a linear model (P < 0.001) in all of the experimental conditions. The following formula fitted the experimental points with an error <2% for both postdilutional and predilutional online diafiltration in vitro, respectively. K = K0 + [(QB - K0)/(QB)] x ultrafiltration rateK = K0 + [((QD x QB)/(QB + QD) - K0)/QD] x ultrafiltration rate where K is the clearance; K0 is the clearance with nil ultrafiltration rate; QD is the total dialysate produced (in commercial HDF, QD = QDi + Qinf). Since weight loss was maintained at 0, ultrafiltration rate = infusion flow. QB is the "blood" line flow. The formula was also verified in vivo in clinical postdilutional hemodiafiltration with a QB taking into account the cellular and water compartments.

DISCUSSION

In vitro, by simply determining the clearance in conventional dialysis, the total clearance for any ultrafiltration rate may be estimated in both predilutional and postdilutional online diafiltration with an error of less than 2%. The same applies to in vivo postdilutional hemodiafiltration when the formula takes into account the cellular and water composition of blood.

Dependence of peritoneal clearances on body size in continuous ambulatory peritoneal dialysis: effect of the normalizing size indicator

In peritoneal dialysis (PD), small solute clearances are normalized by body water (V) and body surface area (BSA). The purpose of this study was to identify if V or BSA produced stronger associations between body size and normalized clearances. We studied the relationship between four size indicators (V, BSA, height, and weight) and either peritoneal urea clearance normalized to V (Kt/V(ur)) and BSA (C(ur)) or creatinine clearance normalized to V (Kt/V(cr)) and BSA (C(cr)). A total of 613 clearance studies were performed in subjects on continuous ambulatory peritoneal dialysis (CAPD) with four daily exchanges and a 2 L fill volume. As size increased, the normalized peritoneal clearances decreased in a nonlinear fashion (regression: y = b0 + b1x(-1), where x is a size indicator and y is a normalized clearance). Significant (p < 0.001) negative correlations were found between each normalized clearance and each size indicator. However, in each case, the correlation was higher when V, rather than BSA, was used. For example, BSA correlated more closely with K/V(ur)(-0.660) than C(ur)(-0.556), and also with Kt/V(cr)(-0.579) than C(cr)(-0.446). Normalized clearances are smaller in large subjects on CAPD because one mathematic determinant of the clearance, the drain volume (Dv) normalized by V (Dv/V) or BSA (DV/BSA), decreases as size increases. The relationship between Dv/V or Dv/BSA and the size indicators was studied by the same nonlinear regression model. The correlations of the size indicators with Dv/V were also consistently higher than the corresponding correlations with Dv/BSA. In subjects who were on the same PD schedule, the dependence of clearances on size was consistently higher when V, rather than BSA, was the normalizing parameter. Because prescription of the dose of PD is based on body size, there is a practical advantage by using V as the sole normalizing parameter for both urea and creatinine clearance.

The relation between body size and normalized small solute clearances in continuous ambulatory peritoneal dialysis

The normalized peritoneal clearances of small solutes depend on the ratio of their concentration in dialysate and plasma (D/P) and the drain volume (Dv) corrected for some measure of body size such as body water (V) or body surface area (BSA). The clearance formulas (D/P) x (Dv/V) and (D/ P) x (Dv/BSA) can be used to examine why large individuals tend to be underdialyzed. Large people have low normalized drain volumes (Dv/V, Dv/BSA). It is not known whether size affects the D/P ratios. The purpose of this study was to examine the relationship between normalized peritoneal clearances (Kt/Vurea, CCr per 1.73 m2 BSA) and four size indicators (weight, height, V, BSA) in 301 patients on continuous ambulatory peritoneal dialysis (four daily exchanges with 2-L exchange volume) who underwent 613 clearance studies. Highly significant (P < 0.001) nonlinear relationships were found between Kt/Vurea and weight (r2 = 0.371), height (r2 = 0.289), BSA (r2 = 0.436), and V (r2 = 0.527); and between CCr and weight (r2 = 0.178), height (r2 = 0.115), BSA (r2 = 0.199), and V (r2 = 0.151). There were also significant negative correlations between the normalized drain volumes (Dv/V and Dv/BSA) and all four indicators of body size. Raw (not normalized) peritoneal clearances and drain volumes correlated positively with size. However, D/P(urea) or D/P(creatinine) did not vary with any size indicator except for a weak association between D/P(creatinine) and V (r = 0.089, P = 0.028). This association was not confirmed when V was used to stratify subjects into quartiles, and group differences for D/P(creatinine were tested by one-way ANOVA. This study shows that the exclusive cause of the low normalized peritoneal clearances in large subjects on continuous ambulatory peritoneal dialysis is a low normalized drain volume. No evidence was found to indicate that body size influences the D/P ratio of small solutes. The portion of the variance in normalized clearance explained by size varies by size indicator and solute (urea versus creatinine).

Cycler adequacy and prescription data in a national cohort sample: the 1997 core indicators report. Health Care Financing Administration Peritoneal Dialysis Core Indicators Study Group

BACKGROUND

The Health Care Financing Administration Peritoneal Dialysis Core Indicator Project obtains data yearly in four areas of patient care: dialysis adequacy, anemia, blood pressure, and nutrition.

METHODS

Adequacy and dialysis prescription data were obtained using a standardized data abstraction form from a random sample of adult U.S. peritoneal dialysis patients who were alive on December 31, 1996.

RESULTS

For the cohort receiving cycler dialysis, 22% were unable to meet the National Kidney Foundation Dialysis Outcome Quality Initiatives (NKF-DOQI) dialysis adequacy guidelines because they did not have at least one adequacy measure during the six-month period of observation. Thirty-six percent of patients met NKF-DOQI guidelines for weekly Kt/V urea, 33% met guidelines for weekly creatinine clearance (CCr), and 24% met guidelines for both urea and creatinine clearances. The mean weekly adequacy values were 2.24 +/- 0.56 for Kt/V urea and 67.5 +/- 24.4 liter/1.73 m2 for CCr, and the median values were 2.20 and 62.25 liter/1.73 m2, respectively. The mean prescribed 24-hour volume was 12,040 +/- 3255 ml, and the median prescribed volume was 11,783 ml. Only 60% of patients were prescribed at least one daytime dwell. By logistic regression analysis, risk factors for an inadequate dose of dialysis included being in the highest quartile of body surface area (odds ratio = 3.3 for CCr and 3.4 for Kt/V urea) and a duration of dialysis greater than two years (odds ratio = 4.2 for CCr and 2.1 for Kt/V urea).

CONCLUSION

There is much room for improvement in providing an adequate dose of dialysis to cycler patients. Practitioners should be more aggressive in increasing dwell volumes, adding daytime dwells, and adjusting nighttime dwell times in order to compensate for the loss of residual renal function over time. These changes can only be accomplished if practitioners measure periodically the dose of dialysis as outlined in the NKF-DOQI guidelines.