Approach to fluid management in peritoneal dialysis: a practical algorithm

Diagnosis and treatment of hypertension in dialysis patients: a systematic review

In patients with end-stage renal disease (ESRD) undergoing dialysis, hypertension is common but often inadequately controlled. The prevalence of hypertension varies widely among studies because of differences in the definition of hypertension and the methods of used to measure blood pressure (BP), i.e., peri-dialysis or ambulatory BP monitoring (ABPM). Recently, ABPM has become the gold standard for diagnosing hypertension in dialysis patients. Home BP monitoring can also be a good alternative to ABPM, emphasizing BP measurement outside the hemodialysis (HD) unit. One thing for sure is pre- and post-dialysis BP measurements should not be used alone to diagnose and manage hypertension in dialysis patients. The exact target of BP and the relationship between BP and all-cause mortality or cause-specific mortality are unclear in this population. Many observational studies with HD cohorts have almost universally reported a U-shaped or even an L-shaped association between BP and all-cause mortality, but most of these data are based on the BP measured in HD units. Some data with ABPM have shown a linear association between BP and mortality even in HD patients, similar to the general population. Supporting this, the results of meta-analysis have shown a clear benefit of BP reduction in HD patients. Therefore, further research is needed to determine the optimal target BP in the dialysis population, and for now, an individualized approach is appropriate, with particular emphasis on avoiding excessively low BP. Maintaining euvolemia is of paramount importance for BP control in dialysis patients. Patient heterogeneity and the lack of comparative evidence preclude the recommendation of one class of medication over another for all patients. Recently, however, β-blockers could be considered as a first-line therapy in dialysis patients, as they can reduce sympathetic overactivity and left ventricular hypertrophy, which contribute to the high incidence of arrhythmias and sudden cardiac death. Several studies with mineralocorticoid receptor antagonists have also reported promising results in reducing mortality in dialysis patients. However, safety issues such as hyperkalemia or hypotension should be further evaluated before their use.

Urgent-start peritoneal dialysis

Peritoneal dialysis is an important form of kidney replacement therapy. Most patients presenting with an unplanned, urgent need for dialysis are prescribed haemodialysis, leading to peritoneal dialysis underutilisation. Urgent-start peritoneal dialysis refers to treatment that is commenced within 2 weeks of catheter placement. Urgent-start peritoneal dialysis represents an efficacious, cost-effective alternative to the conventional approach of commencing dialysis. There is a paucity of evidence to guide management, however experience with the technique is increasing. This article overviews the rationale and practical application of urgent-start peritoneal dialysis.

Inflammation and Extracellular Volume Expansion are Related to Sodium and Water Removal in Patients on Peritoneal Dialysis

Background

Inflammation is an important risk for mortality in dialysis patients. Extracellular fluid volume (ECFv) expansion, a condition commonly seen in peritoneal dialysis (PD) patients, may be associated with inflammation. However, published support for this relationship is scarce.

Objectives

To quantify the proportion of patients on PD with inflammation and to analyze the role of ECFv expansion and the factors related to these conditions.

Design

A prospective, multicenter cross-sectional study in six hospitals with a PD program.

Patients and Methods

Adult patients on PD were studied. Clinical data, body composition, and sodium and fluid intake were recorded. Biochemical analysis, C-reactive protein (CRP), and peritoneal and urinary fluid and sodium removal were also measured.

Results

CRP values positive (≥ 3.0 mg/L) for inflammation were found in 147 (80.3%) and negative in 36 patients. Patients with positive CRP had higher ECFv/total body water (TBW) ratio (women 47.69 ± 0.69 vs 47.36 ± 0.65, men 43.15 ± 1.14 vs 42.84 ± 0.65; p < 0.05), higher serum glucose (125.09 ± 81.90 vs 103.28 ± 43.30 mg/dL, p < 0.03), and lower serum albumin (2.86 ± 0.54 vs 3.17 ± 0.38 g/dL, p < 0.001) levels. They also had lower ultrafiltration (1003 ± 645 vs 1323 ± 413 mL/day, p < 0.005) and total fluid removal (1260 ± 648 vs 1648 ± 496 mL/day, p < 0.001), and less peritoneal (15.59 ± 162.14 vs 78.11 ± 110.70 mEq/day, p < 0.01) and total sodium removal (42.06 ± 142.49 vs 118.60 ± 69.73 mEq/day, p < 0.001). In the multivariate analysis, only ECFv/TBW was significantly ( p < 0.04) and independently associated with inflammation. ECFv/TBW was correlated with fluid removal ( r = 0.16, p < 0.03) and renal sodium removal ( r = 0.2, p < 0.01).

Conclusion

The data suggest that ECFv expansion may have a significant role as an inflammatory stimulus. The results disclose a relationship between the two variables, ECFv expansion and inflammation, identified as independent risk factors for mortality in PD patients.

Combination of Crystalloid (Glucose) and Colloid (Icodextrin) Osmotic Agents Markedly Enhances Peritoneal Fluid and Solute Transport during the Long PD Dwell

Background

Fluid and sodium removal is often inadequate in peritoneal dialysis patients with high peritoneal solute transport rate, especially when residual renal function is declining.

Method

We studied the effects of using simultaneous crystalloid (glucose) and colloid (icodextrin) osmotic agents on the peritoneal transport of fluid, sodium, and other solutes during 15-hour single-dwell exchanges using 3.86% glucose, 7.5% icodextrin, and a combination fluid with 2.61% glucose and 6.8% icodextrin in 7 prevalent peritoneal dialysis patients with fast peritoneal solute transport rate.

Results

The combination fluid enhanced net ultrafiltration (mean 990 mL) and sodium removal (mean 158 mmol) compared with 7.5% icodextrin (mean net ultrafiltration 462 mL, mean net sodium removal 49 mmol). In contrast, the 3.86% glucose-based solution yielded negligible ultra-filtration (mean -85 mL) and sodium removal (mean 16 mmol). The combination solution resulted in significantly improved urea (+41%) and creatinine (+26%) clearances compared with 7.5% icodextrin.

Conclusion

A solution containing both crystalloid (glucose 2.61%) and colloid (icodextrin 6.8%) osmotic agents enhanced fluid removal by twofold and sodium removal by threefold compared with 7.5% icodextrin solution during a dwell of 15 hours, indicating that such a combination solution could represent a new treatment option for anuric peritoneal dialysis patients with high peritoneal solute transport rate.

Factors Contributing to Formation of Edema in Volume Overloaded Continuous Ambulatory Peritoneal Dialysis Patients

Background

Volume control is critical for the success of peritoneal dialysis (PD) but dry weight in PD has been difficult to obtain. Edema free is, in general, accepted clinically as a target for volume control in PD patients. However, PD patients can be free of edema despite significant volume overload. The present study investigates the possible factors that influence the formation of pitting edema in volume-overloaded PD patients.

Methods

In this cross-sectional study, patients’ fluid status was evaluated by multifrequency bioelectrical impedance spectroscopy analysis. Values for overhydration were obtained. Patients with overhydration ≥ 2.0 kg were considered volume overloaded and were eligible for inclusion. From 1 March 2009 to 1 December 2009, a total of 96 patients on continuous ambulatory PD were included. Endothelial function was evaluated by flow-mediated dilatation (FMD). Other clinical indicators, such as blood pressure, dialysis adequacy, nutrition status, and biochemical parameters, were recorded. Patients were divided into 2 groups based on edema status: the edema group ( n = 35 volume-overloaded patients with bilateral pitting edema) and the non-edema group ( n = 61 volume-overloaded patients without bilateral pitting edema).

Results

Overhydration in the edema group was significantly higher than in the non-edema group (4.28 ± 1.75 kg vs 3.12 ± 0.81 kg, p < 0.001), whereas both FMD and serum albumin in the edema group were significantly lower than in the non-edema group (6.65% ± 5.2% vs 10.3% ± 5.1%, p = 0.001; 37.6 ± 4.2 g/L vs 39.3 ± 3.5 g/L, p = 0.047, respectively). Edema status (edema = 1, non-edema = 0) was positively correlated with overhydration ( r = 0.341, p < 0.001), gender (male = 1, female = 2: r = 0.184, p = 0.072), and total fluid removal ( r = 0.188, p = 0.074) and negatively correlated with endothelial function, as assessed by FMD ( r = -0.33, p = 0.001), and serum albumin ( r = -0.18, p = 0.055). Logistic regression analysis showed that FMD [odds ratio (OR) 0.90, 95% confidence interval (CI) 0.81 - 0.99; p = 0.036], gender (male = 1, female = 2: OR 4.06, 95% CI 1.23 - 13.35; p = 0.021), overhydration (OR 3.06, 95% CI 1.53 - 6.13; p = 0.002), and serum albumin (OR 0.86, 95% CI 0.75 - 0.99; p = 0.035) were independent factors affecting the edema status of the study population.

Conclusion

Our study showed that endothelial function (assessed by FMD), gender, serum albumin, and over hydration are independent determinants of edema status in PD patients. This may explain why some PD patients can maintain free of edema despite significant volume overload.

Quantitative Lung Ultrasound Comet Measurement: Method and Initial Clinical Results

<b><i>Background/Aims:</i></b> Recently, ultrasound signals termed ‘lung water comets' associated with pulmonary edema have been correlated with adverse clinical events in dialysis patients. These comets fluctuate substantially during the ultrasound exam highlighting the need for objective quantitative measurement methods. <b><i>Methods:</i></b> We developed an image-processing algorithm for the detection and quantification of lung comets. Quantification measures included comet number (comet count) and the fraction of the ultrasound beams with comet findings (comet fraction). We used this algorithm in a pilot study in 20 stable dialysis outpatients to identify associations between ultrasound comets and clinical parameters including blood pressure (BP), percent blood volume reduction on dialysis (%BV), ejection fraction (EF), and ultrafiltration on dialysis (UF). <b><i>Results:</i></b> Positive findings included associations with lung comet measurements with pre-dialysis Diastolic BP (r = 0.534, p = 0.015), subject age (r = -0.446, p = 0.049), and a combination of EF and end dialysis %BV reduction (r = -0.585, p = 0.028). Comet fraction and comet count were closely correlated due to the inherent relationship between these two metrics (r = 0.973, p < 0.001). Negative findings included ultrasound comets that did not change from beginning to end of dialysis (p = 0.756), and were not significantly correlated with single dialysis treatment UF (p = 0.522), subject body weight (p = 0.208), or BMI (p = 0.358). <b><i>Conclusions:</i></b> Ultrasound signal processing methods may help quantify lung ultrasound comets. Additional findings include algorithmic lung comet measurement that did not change significantly during single dialysis sessions in these stable outpatients, but were associated with cardiovascular and fluid status parameters.

Salt and Fluid Intake in the Development of Hypertension in Peritoneal Dialysis Patients

BACKGROUND

Although fluid overload contributes to hypertension in CAPD patients, less attention has been paid to the role of excess salt and fluid intake. Therefore, we investigated the role of salt and fluid intake in the development of hypertension in CAPD patients.

METHODS

A total of 165 stable CAPD patients were included into this study. Based on the blood pressure in three consecutive months, they were divided into three groups: persistent hypertensive (PH; n = 33), intercurrent hypertensive (IH; n = 58) and persistent normotensive (PN; n = 74). The IH group was further divided into two phases: normotensive and hypertensive. Fluid status was evaluated by clinical assessment and bioimpedance analysis (BIA).

RESULTS

There were no differences in age, gender, and duration of dialysis among groups. Patients were more fluid overloaded in the PH group. Extracellular water (ECW), total body water (TBW), and normalized extracellular water by height (NECW) were higher in the PH group than the PN group (16.77 +/- 3.62 L vs. 14.61 +/- 2.92 L for ECW, p < 0.01; 32.22 +/- 8.23 L vs. 28.98 +/- 6.00 L for TBW, p < 0.05; and 10.28 +/- 1.86 L/m vs. 9.08 +/- 1.63 L/m for NECW, p < 0.01). However, patients in the PH group also had more total fluid removal (TFR) and total sodium removal (TSR) compared with the PN group (1346.82 +/- 431.27 mL/d vs. 1139.28 +/- 412.65 mL/d for TFR, p < 0.05; and 141.52 +/- 61.57 mmol/d vs. 102.42 +/- 62.51 mmol/d for TSR, p < 0.01). The same trend was demonstrated when compared values of hypertensive and normotensive phase in IH group; patients had higher ECW, TBW, NECW, TSR, and PNa when they were in hypertensive phase than in the normotensive phase.

CONCLUSIONS

This study confirmed that fluid overload was closely associated with the development of hypertension in CAPD patients. It also showed that hypertensive patients were in general more fluid overloaded despite a higher fluid and sodium removal as compared with normotensive patients.

The role of peritoneal dialysis in the management of treatment-resistant congestive heart failure: A European perspective

Patients with congestive heart failure (CHF) resistant to conventional treatment have a poor prognosis. Extracorporeal ultrafiltration (UF) appears to be the therapy of choice for short-term management of such patients with severe fluid overload, whereas peritoneal dialysis (PD) may be the therapy of choice for the long-term treatment. Fluid removal results in reduction of plasma volume, improvement of hyponatremia, reduction in pulmonary capillary wedge pressure, improvement of New York Heart Association functional heart failure class, improvement of functional rehabilitation and quality of life, reduction of hospitalizations and readmissions, as well as improvement in diuretic responsiveness. Whether extracorporeal UF and/or PD modifies the survival rate of patients with refractory CHF needs to be determined in prospective randomized controlled trials.

Diabetic patients can do as well on peritoneal dialysis as nondiabetic patients

BACKGROUND

It is not uncommon that diabetic peritoneal dialysis (PD) patients are volume overloaded and this may have contributed to the inferior outcome of diabetic patients. In the present cohort study, we compared the difference between diabetics and nondiabetics during the first year of PD after implementing strict volume control.

METHODS

Seventeen diabetic and 40 nondiabetic incident PD patients were followed for 1 year. Fluid status was evaluated by bioimpedance analysis and blood pressure. Nutritional status was evaluated by subjective global nutritional assessment.

RESULTS

At the initiation, compared with the nondiabetics, diabetics had a significantly higher extracelluar volume, systolic blood pressure and lower serum albumin. One year later, there were no statistical differences in these parameters between the two groups. The prevalence of malnutrition decreased in all patients, although malnutrition remained slightly higher in diabetic patients.

CONCLUSIONS

Our study suggests that diabetics can do as well as nondiabetics on PD. Appropriate diabetic care, especially strict volume control, may be critical for the success of diabetic patients on PD treatment.