Weekly Standard Kt/Vurea and Clinical Outcomes in Home and In-Center Hemodialysis

Abstract

Background and objectives: Patients undergoing hemodialysis with a frequency other than thrice weekly are not included in current clinical performance metrics for dialysis adequacy. The weekly standard Kt/V_urea incorporates treatment frequency, but there are limited data on its association with clinical outcomes.

Design, setting, participants, & measurements: We used multivariable regression to examine the association of dialysis standard Kt/V_urea with BP and metabolic control (serum potassium, calcium, bicarbonate, and phosphorus) in patients incidental to dialysis treated with home (n=2373) or in-center hemodialysis (n=109,273). We further used Cox survival models to examine the association of dialysis standard Kt/V_urea with mortality, hospitalization, and among patients on home hemodialysis, transfer to in-center hemodialysis.

Results: After adjustment for potential confounders, patients with dialysis standard Kt/V_urea <2.1 had higher BPs compared with patients with standard Kt/V_urea 2.1 to <2.3 (3.4 mm Hg higher [P<0.001] for home hemodialysis and 0.9 mm Hg higher [P<0.001] for in-center hemodialysis). There were no clinically meaningful associations between dialysis standard Kt/V_urea and markers of metabolic control, irrespective of dialysis modality. There was no association between dialysis standard Kt/V_urea and risk for mortality, hospitalization, or transfer to in-center hemodialysis among patients undergoing home hemodialysis. Among patients on in-center hemodialysis, dialysis standard Kt/V_urea <2.1 was associated with higher risk (adjusted hazard ratio, 1.11; 95% confidence interval, 1.07 to 1.14) and standard Kt/V_urea ≥2.3 was associated with lower risk (adjusted hazard ratio, 0.97; 95% confidence interval, 0.94 to 0.99) for death compared with standard Kt/V_urea 2.1 to <2.3. Additional analyses limited to patients with available data on residual kidney function showed similar relationships of dialysis and total (dialysis plus kidney) standard Kt/V_urea with outcomes.

Conclusions: Current targets for standard Kt/V_urea have limited utility in identifying individuals at increased risk for adverse clinical outcomes for those undergoing home hemodialysis but may enhance risk stratification for in-center hemodialysis.

Keywords: Bicarbonates; Blood Pressure Determination; Confidence Intervals; Epidemiology and outcomes; Hemodialysis, Home; Odds Ratio; Phosphorus; Potassium; Risk; blood pressure; calcium bicarbonate; hemodialysis adequacy; hospitalization; mortality risk; renal dialysis.

Graphical abstract

Figure 1.

Single-pool Kt/V (spKt/V) and standard Kt/V (stdKt/V) in patients undergoing home and in-center hemodialysis are closely correlated after accounting for dialysis treatment frequency. (A) Home hemodialysis linear correlation coefficients: 0.93 for weekly treatment frequency =3, 0.92 for frequency =4, 0.91 for frequency =5, 0.92 for frequency =6, and 0.90 for frequency =7. (B) In-center hemodialysis linear correlation coefficients: 0.79 for weekly treatment frequency =2, 0.87 for frequency =3, 0.83 for frequency =4, and 0.86 for frequency =5.

Figure 2.

Dialysis standard Kt/V (stdKt/V) was not associated with all-cause mortality, hospitalization, or transfer to in-center hemodialysis (HD) in patients undergoing home HD. Cubic splines shown are from models adjusted for age, sex, race/ethnicity, body mass index, diabetes status, history of congestive heart failure, history of atherosclerotic heart disease, vascular access type, and serum albumin. Solid lines represent 95% confidence intervals.

Figure 3.

Spline analyses suggested that dialysis stdKt/V less than that typically achieved in clinical practice was associated with higher mortality and hospitalization among patients undergoing in-center hemodialysis. Cubic splines shown are from models adjusted for age, sex, race/ethnicity, body mass index, diabetes status, history of congestive heart failure, history of atherosclerotic heart disease, vascular access type, and serum albumin. Solid lines represent 95% confidence intervals.

Figure 4.

Restricting analyses to patients on in-center hemodialysis with available data on residual native kidney function (n=31,748) did not change the observed association of dialysis stdKt/V with all-cause mortality. Data shown are from models adjusted for age, sex, race/ethnicity, body mass index, diabetes status, history of congestive heart failure, history of atherosclerotic heart disease, vascular access type, and serum albumin. Dialysis stdKt/V models are additionally adjusted for kidney stdKt/V; kidney stdKt/V models are additionally adjusted for dialysis stdKt/V. Solid lines represent 95% confidence intervals.