Hemodialysis Ultrafiltration Rate Targets Should Be Scaled to Body Surface Area Rather than to Body Weight

The role of plasma volume and fluid overload in the tolerance to ultrafiltration and hypotension in hemodialysis patients

INTRODUCTION

Ultrafiltration (UF) in hemodialysis (HD) patients is accompanied by irregular falls in plasma volume (PV) and blood pressure (BP).

METHODS

We obtained in 321 patients (large cohort), body weight (BW), BP, samples of blood to determine hemoglobin (Hb) and hematocrit (Ht), Pre and Post HD. We estimated the % variation of the PV and its effect on the BP. In a small cohort of 38/321 patients, arterial blood was drawn Pre and Post HD and at 2, 48, and 72 h to determined Hb and Ht and % variation of the PV. Bio-impedance spectroscopy (BIS) was performed, in the same times, to estimate: dry weight (DW), total body water (TBW), extracellular water (ECW), Fluid overload (FO) and phase angle (PhA).

RESULTS

We divided our large cohort in two groups. The Hypotensive group with a fall equal or more than 20 mmHg (96/321,30%) and Normotensive group with a drop equal or less than 19 mmHg (225/321,70%). The UF was 2.73 ± 0.72 L in the Hypotensive group and 2.53 ± 0.85 L in the Normotensive group (p < 0.0001). The % PV was -11.7 ± 17.8 in the Hypotensive group and -8.53 ± 10.07 in the Normotensive group (p < 0.0001). The systolic blood pressure (SBP) correlated with the % change of the PV (r = -0.232; p < 0.0001). The FO was contrasted with the % of water removed by UF (r = -0.890; p < 0.0001).

CONCLUSION

The SBP drop was secondary to the fall in the PV after UF. The FO was irregular and modulates in part the fall in the SBP.

Body surface area and treatment failure in peritoneal dialysis-associated peritonitis

INTRODUCTION

This study mainly discussed the relationship between body surface area (BSA) and treatment failure of peritoneal dialysis-associated peritonitis (PDAP).

METHODS

The exposures were BSA grouped by the tertiles of BSA levels. The association between BSA and the risk of treatment failure in PDAP, defined as the temporary or permanent switch to hemodialysis and kidney transplantation, was evaluated in Cox proportional hazards models.

RESULTS

A total of 483 episodes in 285 patients were recorded in our center. As a three-level categorical variable, in reference to G3, the G1 of BSA displayed a 4.054-fold increased venture of treatment failure in a fully adjusted model. In sensitivity analysis, a lower value of BSA (G1) was identified as an independent risk factor for peritonitis episodes (odds ratio = 2.433, 95% confidence interval: 1.184-4.999, p = 0.015).

CONCLUSION

A lower level of body surface area was remarkably associated with a higher incidence of treatment failure among peritoneal dialysis-associated peritonitis episodes.

Ultrafiltration-induced decrease in relative blood volume is larger in hemodialysis patients with low specific blood volume: Results from a dialysate bolus administration study

INTRODUCTION

Prescribing the ultrafiltration in hemodialysis patients remains challenging and might benefit from the information on absolute blood volume, estimated by intradialytic dialysate bolus administration. Here, we aimed at determining the relationship between absolute blood volume, normalized for body mass (specific blood volume, Vs), and ultrafiltration-induced decrease in relative blood volume (∆RBV) as well as clinical parameters including body mass index (BMI).

METHODS

This retrospective analysis comprised 77 patients who had their dialysate bolus-based absolute blood volume extracted routinely with an automated method. Patient-specific characteristics and ∆RBV were analyzed as a function of Vs, dichotomizing the data above or below a previously proposed threshold of 65 ml/kg for Vs. Statistical methodology comprised descriptive analyses, two-group comparisons, and correlation analyses.

FINDINGS

Median Vs was 68.6 ml/kg (54.9 ml/kg [Quartile 1], 83.4 ml/kg [Quartile 3]). Relative blood volume decreased by 6.3% (2.6%, 12.2%) over the entire hemodialysis session. Vs correlated inversely with BMI (r_s  = -0.688, p < 0.001). ∆RBV was 9.8% in the group of patients with Vs <65 ml/kg versus 6.0% in the group of patients with Vs ≥65 ml/kg (p = 0.024). The two groups did not differ significantly regarding their specific ultrafiltration volume, normalized for body mass, which amounted to 34.1 ml/kg and 36.0 ml/kg in both groups, respectively (p = 0.630). ∆RBV correlated inversely with Vs (r_s  = -0.299, p = 0.008).

DISCUSSION

The present study suggests that patients with higher BMI and lower Vs experience larger blood volume changes, despite similar ultrafiltration requirements. These results underline the clinical plausibility and importance of dialysate bolus-based absolute blood volume determination in the assessment of target weight, especially in view of a previous study where intradialytic morbid events could be decreased when the target weight was adjusted, based on Vs.

Ultrafiltration rate thresholds associated with increased mortality risk in hemodialysis, unscaled or scaled to body size

Introduction

One proposed threshold ultrafiltration rate (UFR) of concern in hemodialysis patients is 13 ml/h per kg. We evaluated associations among UFR, postdialysis weight, and mortality to determine whether exceeding such a threshold would result in similar levels of risk for patients of different body weights.

Methods

Data were analyzed in this retrospective cohort study for 1 year following dialysis initiation (baseline) and over 2 years of follow-up in incident patients receiving thrice-weekly in-center hemodialysis. Patient-level UFR was averaged over the baseline period. To investigate the joint effect of UFR and postdialysis weight on survival, we fit Cox proportional hazards models using bivariate tensor product spline functions, adjusting for sex, race, age, diabetes, and predialysis serum albumin, phosphorus, and systolic blood pressure (BP). We constructed contour plots of mortality hazard ratios (MHRs) over the entire range of UFR values and postdialysis weights.

Results

In the studied 2542 patients, UFR not scaled to body weight was strongly associated with MHR, whereas postdialysis weight was inversely associated with MHR. MHR crossed 1.5 when unscaled UFR exceeded 1000 ml/h, and this relationship was largely independent of postdialysis weight in the range of 80 to 140 kg. A UFR warning level associated with a lower MHR of 1.3 would be 900 ml/h, whereas the UFR associated with an MHR of 1.0 was patient-size dependent. The MHR when exceeding a UFR threshold of 13 ml/h per kg was dependent on patient weight (MHR = 1.20, 1.45, and >2.0 for a 60, 80, and 100 kg patient, respectively).

Conclusion

UFR thresholds based on unscaled UFR give more uniform risk levels for patients of different sizes than thresholds based on UFR/kg.

The spectrum of kidney dysfunction requiring chronic dialysis therapy: Implications for clinical practice and future clinical trials

Staging to capture kidney function and pathophysiologic processes according to severity is widely used in chronic kidney disease or acute kidney injury not requiring dialysis. Yet the diagnosis of "end-stage kidney disease" (ESKD) considers patients as a single homogeneous group, with negligible kidney function, in need of kidney replacement therapy. Herein, we review the evidence behind the heterogeneous nature of ESKD and discuss potential benefits of recasting the terminology used to describe advanced kidney dysfunction from a monolithic entity to a disease with stages of ascending severity. We consider kidney assistance therapy in lieu of kidney replacement therapy to better reconcile all available types of therapy for advanced kidney failure including dietary intervention, kidney transplantation, and dialysis therapy at varied schedules. The lexicon "kidney dysfunction requiring dialysis" (KDRD) with stages of ascending severity based on levels of residual kidney function (RKF)-that is, renal urea clearance-and manifestations related to uremia, fluid status, and other abnormalities is discussed. Subtyping KDRD by levels of RKF could advance dialysis therapy as a form of kidney assistance therapy adjusted based on RKF and clinical symptoms. We focus on intermittent hemodialysis and underscore the need to personalize dialysis treatments and improve characterization of patients included in clinical trials.

Ultrafiltration rate adjusted to body weight and mortality in hemodialysis patients

BACKGROUND AND AIMS

Mortality among hemodialysis patients remains high. An elevated ultrafiltration rate adjusted by weight (UFR/W) has been associated with hypotension and higher risk of death and/or cardiovascular events.

METHODS

We evaluated the association between UFR/W and mortality in 215 hemodialysis patients. The mean follow-up was 28 ± 6.12 months. We collected patients' baseline characteristics and mean UFR/W throughout the follow-up.

RESULTS

Mean UFR/W was 9.0 ± 2,4 and tertiles 7.1 y 10.1 mL/kg/h. We divided our population according to the percentage of sessions with UFR/W above the limits described in the literature associated with increased mortality (10.0 ml/kg/h and 13.0 mL/kg/h). Patients with higher UFR/W were younger, with higher interdialytic weight gain and weight reduction percentage but lower dry, pre and post dialysis weight. Throughout the follow-up, 46 (21.4%) patients died, the majority over 70 years old, diabetic or with cardiovascular disease. There were neither differences regarding mortality between groups nor differences in UFR/W among patients who died and those who did not. Contrary to previous studies, we did not find an association between UFR/W and mortality, maybe due to a higher prevalence in the use of cardiovascular protection drugs and lower UFR/W.

CONCLUSIONS

The highest UFR/W were observed in younger patients with lower weight and were not associated with an increased mortality.

Ultrafiltration rate adjusted to body weight and mortality in hemodialysis patients

BACKGROUND AND AIMS

Mortality among hemodialysis patients remains high. An elevated ultrafiltration rate adjusted by weight (UFR/W) has been associated with hypotension and higher risk of death and/or cardiovascular events.

METHODS

We evaluated the association between UFR/W and mortality in 215 hemodialysis patients. The mean follow-up was 28 ± 6.12 months. We collected patientś baseline characteristics and mean UFR/W throughout the follow-up.

RESULTS

Mean UFR/W was 9.0 ± 2,4 and tertiles 7.1 y 10.1 mL/kg/h. We divided our population according to the percentage of sessions with UFR/W above the limits described in the literature associated with increased mortality (10.0 mL/kg/h and 13.0 mL/kg/h). Patients with higher UFR/W were younger, with higher interdialytic weight gain and weight reduction percentage but lower dry, pre and post dialysis weight. Throughout the follow-up, 46 (21.4%) patients died, the majority over 70 years old, diabetic or with cardiovascular disease. There were neither differences regarding mortality between groups nor differences in UFR/W among patients who died and those who did not. Contrary to previous studies, we did not find an association between UFR/W and mortality, maybe due to a higher prevalence in the use of cardiovascular protection drugs and lower UFR/W.

CONCLUSIONS

The highest UFR/W were observed in younger patients with lower weight and were not associated with an increased mortality.

Association between Ultrafiltration Rate and Clinical Outcome Is Modified by Muscle Mass in Hemodialysis Patients

BACKGROUND

The association between ultrafiltration rate (UFR) and mortality may be affected by the muscle mass or volume status in hemodialysis (HD) patients. However, there is an absence of data regarding this association.

METHODS

We performed an observational study on patients (≥18 years old) who had been on HD for at least 3 months. A body composition monitor (BCM) was used for baseline bioimpedance analysis measurement. The primary composite outcome was defined as the time to death or the first cardiovascular event.

RESULTS

The median (interquartile range) UFR, volume excess measured by the BCM, and lean tissue index (LTI) (calculated as lean tissue mass/height2) were 11.4 (8.0-15.0) mL/h/kg, 2.4 (1.4-4.1) L, and 12.5 (10.4-14.4) kg/m2, respectively. During 284 person-years of follow-up, the primary outcome occurred in 44 of the 167 patients (26%). Higher UFR was associated with an increased outcome of death or cardiovascular event; the adjusted hazard ratio (HR) was 1.044 (95% confidence interval [CI]: 1.006-1.083). This association remained consistent even after adjusting for volume excess. However, the association between UFR and the primary outcome was modified by LTI (pinteraction = 0.027); the association was significant in patients with LTI < 12.5 kg/m2, and the HR (95% CI) was 1.050 (1.001-1.102).

CONCLUSION

Higher UFR was associated with an increased risk of a composite outcome of death or cardiovascular event regardless of volume status in HD patients. However, muscle mass may modify the association between higher UFR and increased risk of a composite outcome.

Pediatric intradialytic hypotension: recommendations from the Pediatric Continuous Renal Replacement Therapy (PCRRT) Workgroup

Intradialytic hypotension (IDH) is a common adverse event resulting in premature interruption of hemodialysis, and consequently, inadequate fluid and solute removal. IDH occurs in response to the reduction in blood volume during ultrafiltration and subsequent poor compensatory mechanisms due to abnormal cardiac function or autonomic or baroreceptor failure. Pediatric patients are inherently at risk for IDH due to the added difficulty of determining and attaining an accurate dry weight. While frequent blood pressure monitoring, dialysate sodium profiling, ultrafiltration-guided blood volume monitoring, dialysate cooling, hemodiafiltration, and intradialytic mannitol and midodrine have been used to prevent IDH, they have not been extensively studied in pediatric population. Lack of large-scale studies on IDH in children makes it difficult to develop evidence-based management guidelines. Here, we aim to review IDH preventative strategies in the pediatric population and outlay recommendations from the Pediatric Continuous Renal Replacement Therapy (PCRRT) Workgroup. Without strong evidence in the literature, our recommendations from the expert panel reflect expert opinion and serve as a valuable guide.

Feasibility of Incremental 2-Times Weekly Hemodialysis in Incident Patients With Residual Kidney Function

INTRODUCTION

We hypothesized that at least half of incident hemodialysis (HD) patients on 3-times weekly dialysis could safely start on an incremental, 2-times weekly HD schedule if residual kidney function (RKF) had been considered.

METHODS

RKF is assessed in all our HD patients. This single-center, retrospective cohort study of incident adult HD patients, who survived ≥6 months on a 3-times weekly HD regimen and had a timed urine collection within 3 months of starting HD, assessed each patient's theoretical ability to achieve adequate urea clearance, ultrafiltration rate, and hemodynamic stability if on 2-times weekly HD.

RESULTS

Of the 410 patients in the cohort, we found that 112 (27%) could have optimally and 107 (26%) could have been appropriately considered for 2-times weekly incremental HD. In general, diuretics were underutilized in >50% of subjects who had adequate RKF urea clearance. The optimal 2-times weekly patients had better potassium and phosphorus control. The correlation coefficient of calculated residual kidney urea clearance with 24-hour urine volume and with kinetic model residual kidney clearance was 0.68 and 0.99, respectively.

DISCUSSION

More than 50% of incident HD patients with RKF have adequate kidney urea clearance to be considered for 2-times weekly HD. When additionally ultrafiltration volume and blood pressure stability are taken into account, more than one-fourth of the total cohort could optimally start HD in an incremental fashion.

Hemodialysis Treatment Time: As Important as it Seems?

Hemodialysis treatment time and Kt/V can both be considered to be primary measures of hemodialysis adequacy, because when either goes to zero, mortality is certain in patients without residual kidney function. Treatment time is important, but it needs to be adjusted based on surface-area-normalized Kt/V, residual kidney function, and expected ultrafiltration rate. Rescaling dose of dialysis measured as Kt/V to body surface area prevents ultrashort dialysis in small patients, women, and children with minimal residual kidney function. Most if not all of the observational studies of associations between outcome and dialysis session length are probably confounded by dose targeting bias. Once adequate Kt/V (taking into account body surface area) has been provided, adequate dialysis time probably is most relevant in terms of limiting the need for a high fluid removal rate. The latter may adversely impact survival by causing recurrent ischemia to cardiovascular and other tissues. There is little high-quality evidence at this time to support a minimum 4-hour treatment time for all patients, regardless of body size, solute removal, or residual kidney function. On the other hand, there is little evidence that prolonging weekly treatment time up to 24 hours per week is harmful. The final decision regarding treatment time is best individualized, based on patient acceptability and experience, residual kidney function, body surface-area-normalized Kt/V, and expected ultrafiltration rate.