Hypertension in end-stage renal disease

The role of intra- and interdialytic sodium balance and restriction in dialysis therapies

The relationship between sodium, blood pressure and extracellular volume could not be more pronounced or complex than in a dialysis patient. We review the patients' sources of sodium exposure in the form of dietary salt intake, medication administration, and the dialysis treatment itself. In addition, the roles dialysis modalities, hemodialysis types, and dialysis fluid sodium concentration have on blood pressure, intradialytic symptoms, and interdialytic weight gain affect patient outcomes are discussed. We review whether sodium restriction (reduced salt intake), alteration in dialysis fluid sodium concentration and the different dialysis types have any impact on blood pressure, intradialytic symptoms, and interdialytic weight gain.

Resistant hypertension in dialysis

Hypertension is the most common finding in chronic kidney disease patients, with prevalence ranging from 60% to 90% depending on the stage and etiology of the disease. It is also a significant independent risk factor for cardiovascular disease, progression to end-stage kidney disease and mortality. According to the current guidelines, resistant hypertension is defined in the general population as uncontrolled blood pressure on three or more antihypertensive drugs in adequate doses or when patients are on four or more antihypertensive drug categories irrespective of the blood pressure control, providing that antihypertensive treatment included diuretics. The currently established definitions of resistant hypertension are not directly applicable to the end-stage kidney disease setting. The diagnosis of true resistant hypertension requires confirmation of adherence to therapy and confirmation of uncontrolled blood pressure values by ambulatory blood pressure measurement or home blood pressure measurement. In addition, the term "apparent treatment-resistant hypertension," defined as an uncontrolled blood pressure on three or more antihypertensive medication classes, or use of four or more medications regardless of blood pressure level was introduced. In this comprehensive review we focused on the definitions of hypertension, and therapeutic targets in patients on renal replacement therapy, including the limitations and biases. We discussed the issue of pathophysiology and assessment of blood pressure in the dialyzed population, management of resistant hypertension as well as available data on prevalence of apparent treatment-resistant hypertension in end-stage kidney disease. To conclude, larger sample-size and even higher quality studies about drug adherence should be conducted in the population of patients with the end-stage kidney disease who are on dialysis. It also should be determined how and when blood pressure should be measured in the group of dialysis patients. Additionally, it should be stated what the target blood pressure values in this group of patients really are. The definition of resistant hypertension in this group should be revisited, and its relationship to both subclinical and clinical endpoints should be established.

Hypertension in chronic kidney disease: What lies behind the scene

Hypertension is a frequent condition encountered during kidney disease development and a leading cause in its progression. Hallmark factors contributing to hypertension constitute a complexity of events that progress chronic kidney disease (CKD) into end-stage renal disease (ESRD). Multiple crosstalk mechanisms are involved in sustaining the inevitable high blood pressure (BP) state in CKD, and these play an important role in the pathogenesis of increased cardiovascular (CV) events associated with CKD. The present review discusses relevant contributory mechanisms underpinning the promotion of hypertension and their consequent eventuation to renal damage and CV disease. In particular, salt and volume expansion, sympathetic nervous system (SNS) hyperactivity, upregulated renin–angiotensin–aldosterone system (RAAS), oxidative stress, vascular remodeling, endothelial dysfunction, and a range of mediators and signaling molecules which are thought to play a role in this concert of events are emphasized. As the control of high BP via therapeutic interventions can represent the key strategy to not only reduce BP but also the CV burden in kidney disease, evidence for major strategic pathways that can alleviate the progression of hypertensive kidney disease are highlighted. This review provides a particular focus on the impact of RAAS antagonists, renal nerve denervation, baroreflex stimulation, and other modalities affecting BP in the context of CKD, to provide interesting perspectives on the management of hypertensive nephropathy and associated CV comorbidities.

A novel approach to dry weight adjustments for dialysis patients using machine learning

Background and aims

Knowledge of the proper dry weight plays a critical role in the efficiency of dialysis and the survival of hemodialysis patients. Recently, bioimpedance spectroscopy(BIS) has been widely used for set dry weight in hemodialysis patients. However, BIS is often misrepresented in clinical healthy weight. In this study, we tried to predict the clinically proper dry weight (DW_CP) using machine learning for patient’s clinical information including BIS. We then analyze the factors that influence the prediction of the clinical dry weight.

Methods

As a retrospective, single center study, data of 1672 hemodialysis patients were reviewed. DW_CP data were collected when the dry weight was measured using the BIS (DW_BIS). The gap between the two (Gap_DW) was calculated and then grouped and analyzed based on gaps of 1 kg and 2 kg.

Results

Based on the gap between DW_BIS and DW_CP, 972, 303, and 384 patients were placed in groups with gaps of <1 kg, ≧1kg and <2 kg, and ≧2 kg, respectively. For less than 1 kg and 2 kg of GapDW, It can be seen that the average accuracies for the two groups are 83% and 72%, respectively, in usign XGBoost machine learning. As Gap_DW increases, it is more difficult to predict the target property. As Gap_DW increase, the mean values of hemoglobin, total protein, serum albumin, creatinine, phosphorus, potassium, and the fat tissue index tended to decrease. However, the height, total body water, extracellular water (ECW), and ECW to intracellular water ratio tended to increase.

Conclusions

Machine learning made it slightly easier to predict DW_CP based on DW_BIS under limited conditions and gave better insights into predicting DW_CP. Malnutrition-related factors and ECW were important in reflecting the differences between DW_BIS and DW_CP.

Anti-Hypertensive Drug Requirements in Continuous Ambulatory Peritoneal Dialysis

This retrospective analysis documents changes in antihypertensive drug requirements with time on CAPD. In 59 patients who were hypertensive at initiation of CAPD, antihypertensive drug use decreased from almost 1.2 to less than 0.3 drugs per patient during the first month. In this group, the proportion in whom blood pressure was controlled without drugs went from 0% to nearly 60% after 12 months. These results, which most likely reflect control of body -fluid volumes and sodium balance, are similar to those reported with hemodialysis.

It has been noted that patients receiving antihypertensive medications to control blood pressure at the initiation of continuous ambulatory peritoneal dialysis (CAPD) frequently require fewer or no anti-hypertensive medications with time on CAPD (1–2). The purpose of this retrospective analysis was to quantitate the extent and the timing of this trend in a CAPD population at a single center.

The Effect of CAPO on Hypertension Control: A Report of the National CAPO Registry

Hypertension and medication histories were collected on a cohort of 209 randomly selected adult patients from the National CAPD Registry. Seventy-seven percent of the patients had a history of hypertension. Over 92% of hypertensives have a medication history for the problem. Mean reductions in systolic blood pressure of > 11 mm Hg were observed in subsets examined at one month and one year, while diastolic pressure decreases were significant at one month but not at a year. Diuretics were used in 32% of treated hypertensives at baseline, but only 9% of treated patients at one year. With initiation of continuous ambulatory peritoneal dialysis (CAPD), patients are significantly more likely to be classified as normal and less likely to be medically uncontrolled hypertensives. Thirty percent of patients who were receiving antihypertensive medication at baseline were not receiving antihypertensive therapy at one year.

A need for a paradigm shift in focus: From Kt/Vurea to appropriate removal of sodium (the ignored uremic toxin)

Hemodialysis for chronic renal failure was introduced and developed in Seattle, WA, in the 1960s. Using Kiil dialyzers, weekly dialysis time and frequency were established to be about 30 hours on 3 time weekly dialysis. This dialysis time and frequency was associated with 10% yearly mortality in the United States in 1970s. Later in 1970s, newer and more efficient dialyzers were developed and it was felt that dialysis time could be shortened. An additional incentive to shorten dialysis was felt to be lower cost and higher convenience. Additional support for shortening dialysis time was provided by a randomized prospective trial performed by National Cooperative Dialysis Study (NCDS). This study committed a Type II statistical error rejecting the time of dialysis as an important factor in determining the quality of dialysis. This study also provided the basis for the establishment of the Kt/V_urea index as a measure of dialysis adequacy. This index having been established in a sacrosanct randomized controlled trial (RCT), was readily accepted by the HD community, and led to shorter dialysis, and higher mortality in the United States. Kt/V_urea is a poor measure of dialysis quality because it combines three unrelated variables into a single formula. These variables influence the clinical status of the patient independent of each other. It is impossible to compensate short dialysis duration (t) with the increased clearance of urea (K), because the tolerance of ultrafiltration depends on the plasma-refilling rate, which has nothing in common with urea clearance. Later, another RCT (the HEMO study) committed a Type III statistical error by asking the wrong research question, thus not yielding any valuable results. Fortunately, it did not lead to deterioration of dialysis outcomes in the United States. The third RCT in this field ("in-center hemodialysis 6 times per week versus 3 times per week") did not bring forth any valuable results, but at least confirmed what was already known. The fourth such trial ("The effects of frequent nocturnal home hemodialysis") too did not show any positive results primarily due to significant subject recruitment issues leading to inappropriate selection of patients. Comparison of the value of peritoneal dialysis and HD in RCTs could not be completed because of recruitment problems. Randomized controlled trials have therefore failed to yield any meaningful information in the area of dose and or frequency of hemodialysis.

Cardiothoracic Ratio as a Guide to Ultrafiltration Therapy in Dialyzed Patients

This study evaluated the cardiothoracic ratio (CTR) and the roentgenologic heart volume (RHV) as indexes of body fluid retention in 37 uremics on maintenance dialysis therapy. Both indexes related to a highly significant degree with the variations of body fluids balance assessed by the changes in body weights. Cardiomegaly (CTR > .500) subsided with adequate ultrafiltration therapy in most patients including those having blood pressure values within the normal range. It is concluded that the measurements of CTR provides an useful guide to ultrafiltration therapy expecially in those patients whose blood pressure fails to sense the body fluid retention.

Setting the dry weight and its cardiovascular implications

Volume overload is common and associated with adverse outcomes in the hemodialysis population including systemic hypertension, pulmonary hypertension, left ventricular hypertrophy, and mortality. Since the beginning of the era of maintenance dialysis, prescribing and maintaining a dry weight remains the standard of care for managing volume overload on hemodialysis. Reducing dry weight even by relatively small amounts has been shown to improve blood pressure and has been associated with reductions in left ventricular hypertrophy. Maintaining an adequately low dry weight requires attention to sodium intake and adequate time on dialysis, as well as a high index of suspicion for volume overload. Reducing dry weight can provoke decreased cardiac chamber filling and is associated with risks including intradialytic hypotension. The ideal method to minimize intradialytic morbidity is unknown, but more frequent dialysis should be considered. Experimental methods of assessing volume status may allow identification of patients most likely both to tolerate and to benefit from dry weight reduction, but further study is needed.

Interplay of volume, blood pressure, organ ischemia, residual renal function, and diet: certainties and uncertainties with dialytic management

Extracellular fluid volume overload and its inevitable consequence, hypertension, increases cardiovascular mortality in the long term by leading to left ventricular hypertrophy, heart failure, and ischemic heart disease in dialysis patients. Unlike antihypertensive medications, a strict volume control strategy provides optimal blood pressure control without need for antihypertensive drugs. However, utilization of this strategy has remained limited because of several factors, including the absence of a gold standard method to assess volume status, difficulties in reducing extracellular fluid volume, and safety concerns associated with reduction of extracellular volume. These include intradialytic hypotension; ischemia of heart, brain, and gut; loss of residual renal function; and vascular access thrombosis. Comprehensibly, physicians are hesitant to follow strict volume control policy because of these safety concerns. Current data, however, suggest that a high ultrafiltration rate rather than the reduction in excess volume is related to these complications. Restriction of dietary salt intake, increased frequency, and/or duration of hemodialysis sessions or addition of temporary extra sessions during the process of gradually reducing postdialysis body weight in conventional hemodialysis and discontinuation of antihypertensive medications may prevent these complications. We believe that even if an unwanted effect occurs while gradually reaching euvolemia, this is likely to be counterbalanced by favorable cardiovascular outcomes such as regression of left ventricular hypertrophy, prevention of heart failure, and, ultimately, cardiovascular mortality as a result of the eventual achievement of normal extracellular fluid volume and blood pressure over the long term.

Evaluation and Treatment of Hypertension in End-Stage Renal Disease Patients on Hemodialysis

Hypertension is one of the most common cardiovascular comorbidities in end-stage renal disease patients on hemodialysis. Its complex pathophysiology is related to extracellular volume overload, increased vascular resistance stemming from factors related to uremia or abnormal signaling from the failing kidneys, as well as the unique blood pressure changes that take place during and between hemodialysis treatments. Despite the changing nature of blood pressure over time in hemodialysis patients, hypertension diagnosed in or out of the hemodialysis unit is associated with increased cardiovascular morbidity and mortality. This review details the causes of hypertension in hemodialysis patients and provides an updated review of the clinical consequences and management of hypertension.

Review: Blood pressure in haemodialysis patients: The importance of the relationship between the renin-angiotensin-aldosterone system, salt intake and extracellular volume

This review outlines the major mechanisms for control of blood pressure (BP) in individuals with renal failure on haemodialysis. Dietary salt stimulates thirst and, thereby, greater fluid intake with excessive fluid gain between dialysis sessions and chronic expansion of extracellular volume. At the same time, this volume expansion often fails to suppress the renin-angiotensin system (RAS) appropriately and this inevitably leads to high BP in the majority of individuals on haemodialysis.

A greater understanding of the mechanisms involved leads to more rational treatment and better BP control. This can be achieved by careful measurement of BP before and after dialysis, allowing time for the equilibration of extracellular fluid shifts that occur after dialysis, combined with measurements of plasma renin activity. It is relatively easy to then decide how the high BP should be treated either by removal of excess volume by gradual ultrafiltration combined with restriction of salt intake to help prevent thirst and excessive fluid gain between dialyses, or by inhibition of the RAS, or by a combination of both.

In those individuals who are unable to adequately reduce their dietary salt intake and still continue to gain large amounts of weight between dialysis, and are resistant to reducing their pre-dialysis weight, calcium antagonists may help to lower BP, either alone or in combination with RAS blockade. However, the BP often remains resistant to treatment unless they can be persuaded to reduce their salt intake.

Ultrafiltration Rate Thresholds in Maintenance Hemodialysis: An NKF-KDOQI Controversies Report

High hemodialysis ultrafiltration rate (UFR) is increasingly recognized as an important and modifiable risk factor for mortality among patients receiving maintenance hemodialysis. Recently, the Kidney Care Quality Alliance (KCQA) developed a UFR measure to assess dialysis unit care quality. The UFR measure was defined as UFR≥13mL/kg/h for patients with dialysis session length less than 240 minutes and was endorsed by the National Quality Forum as a quality measure in December 2015. Despite this, implementation of a UFR threshold remains controversial. In this NKF-KDOQI (National Kidney Foundation-Kidney Disease Outcomes Quality Initiative) Controversies Report, we discuss the concept of the UFR, which is governed by patients' interdialytic weight gain, body weight, and dialysis treatment time. We also examine the potential benefits and pitfalls of adopting a UFR threshold as a clinical performance measure and outline several aspects of UFR thresholds that require further research.

Controversies and problems of volume control and hypertension in haemodialysis

Extracellular volume overload and hypertension are important contributors to the high risk of cardiovascular mortality in patients undergoing haemodialysis. Hypertension is present in more than 90% of patients at the initiation of haemodialysis and persists in more than two-thirds, despite use of several antihypertensive medications. High blood pressure is a risk factor for the development of left ventricular hypertrophy, heart failure, and mortality, although there are controversies with some study findings showing poor survival with low-but not high-blood pressure. The most frequent cause of hypertension in patients undergoing haemodialysis is volume overload, which is associated with poor cardiovascular outcomes itself independent of blood pressure. Although antihypertensive medications might not be successful to control blood pressure, extracellular volume reduction by persistent ultrafiltration and dietary salt restriction can produce favourable results with good blood pressure control. More frequent or longer haemodialysis can facilitate volume and blood pressure control. However, successful volume and blood pressure control is also possible in patients undergoing conventional haemodialysis.

Cross-sectional association of volume, blood pressures, and aortic stiffness with left ventricular mass in incident hemodialysis patients: the Predictors of Arrhythmic and Cardiovascular Risk in End-Stage Renal Disease (PACE) study

Background

Higher left ventricular mass (LV) strongly predicts cardiovascular mortality in hemodialysis patients. Although several parameters of preload and afterload have been associated with higher LV mass, whether these parameters independently predict LV mass, remains unclear.

Methods

This study examined a cohort of 391 adults with incident hemodialysis enrolled in the Predictors of Arrhythmic and Cardiovascular Risk in End Stage Renal Disease (PACE) study. The main exposures were systolic and diastolic blood pressure (BP), pulse pressure, arterial stiffness by pulse wave velocity (PWV), volume status estimated by pulmonary pressures using echocardiogram and intradialytic weight gain. The primary outcome was baseline left ventricular mass index (LVMI).

Results

Each systolic, diastolic blood, and pulse pressure measurement was significantly associated with LVMI by linear regression regardless of dialysis unit BP or non-dialysis day BP measurements. Adjusting for cardiovascular confounders, every 10 mmHg increase in systolic or diastolic BP was significantly associated with higher LVMI (SBP β = 7.26, 95 % CI: 4.30, 10.23; DBP β = 10.05, 95 % CI: 5.06, 15.04), and increased pulse pressure was also associated with higher LVMI (β = 0.71, 95 % CI: 0.29, 1.13). Intradialytic weight gain was also associated with higher LVMI but attenuated effects after adjustment (β = 3.25, 95 % CI: 0.67, 5.83). PWV and pulmonary pressures were not associated with LVMI after multivariable adjustment (β = 0.19, 95 % CI: −1.14, 1.79; and β = 0.10, 95 % CI: −0.51, 0.70, respectively). Simultaneously adjusting for all main exposures demonstrated that higher BP was independently associated with higher LVMI (SBP β = 5.64, 95 % CI: 2.78, 8.49; DBP β = 7.29, 95 % CI: 2.26, 12.31, for every 10 mmHg increase in BP).

Conclusions

Among a younger and incident hemodialysis population, higher systolic, diastolic, or pulse pressure, regardless of timing with dialysis, is most associated with higher LV mass. Future studies should consider the use of various BP measures in examining the impact of BP on LVM and cardiovascular disease. Findings from such studies could suggest that high BP should be more aggressively treated to promote LVH regression in incident hemodialysis patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0131-4) contains supplementary material, which is available to authorized users.

Epidemiology of hypertension in CKD

Both hypertension (HTN) and CKD are serious interrelated global public health problems. Nearly 30% and 15% of US adults have HTN and CKD, respectively. Because HTN may cause or result from CKD, HTN prevalence is higher and control more difficult with worse kidney function. Etiology of CKD, presence and degree of albuminuria, and genetic factors all influence HTN severity and prevalence. In addition, socioeconomic and lifestyle factors influence HTN prevalence and control. There are racial and ethnic disparities in the prevalence, treatment, risks, and outcomes of HTN in patients with CKD. Control of blood pressure (BP) in Hispanic and African Americans with CKD is worse than it is whites. There are disparities in the patterns of treatment and rates of progression of CKD in patients with HTN. The presence and severity of CKD increase treatment resistance. HTN is also extremely prevalent in patients receiving hemodialysis, and optimal targets for BP control are being elucidated. Although the awareness, treatment, and control of HTN in CKD patients is improving, control of BP in patients at all stages of CKD remains suboptimal.

Assessment and management of hypertension in patients on dialysis

Hypertension is common, difficult to diagnose, and poorly controlled among patients with ESRD. However, controversy surrounds the diagnosis and treatment of hypertension. Here, we describe the diagnosis, epidemiology, and management of hypertension in dialysis patients, and examine the data sparking debate over appropriate methods for diagnosing and treating hypertension. Furthermore, we consider the issues uniquely related to hypertension in pediatric dialysis patients. Future clinical trials designed to clarify the controversial results discussed here should lead to the implementation of diagnostic and therapeutic techniques that improve long-term cardiovascular outcomes in patients with ESRD.

Effect of gradually lowering dialysate sodium concentration on the interdialytic weight gain, blood pressure, and extracellular water in anuric hemodialysis patients

BACKGROUND

The majority of hemodialysis (HD) patients are overhydrated and have high interdialytic weight gain (IDWG) which induces increased blood pressure (BP). The positive sodium balance resulting from a high sodium diet, a high dialysate sodium concentration (DNa), or a combination of both is major causes of this disease. We evaluated the effects of lowering DNa on IDWG, BP, and volume status in anuric HD patients with dietary sodium restriction.

METHODS

Thirty-two patients were enrolled in this study and the period was divided by phase 1 and 2 according to DNa which decreased from 140 to 135 mEq/L at a rate of 1 mEq/L per month; phase 1, 140 mEq/L; phase 2, 135 mEq/L. We compared the IDWG, BP, volume status measured by multifrequency bioimpedance spectroscopy, and adverse events such as intradialytic hypotension, cramps, and headache of both phases.

RESULTS

The IDWG was significantly reduced by 0.39 ± 0.38 kg (p = 0.000). Pre-dialysis BP showed significant reduction (systolic pressure 146 ± 18 vs. 138 ± 22 mmHg; p = 0.012, diastolic pressure 80 ± 10 vs. 75 ± 11 mmHg; p = 0.008). Pre-dialysis extracellular water (ECW) was reduced significantly by 0.13 ± 2.22 L (p = 0.02). There was no significant increase in adverse events (all p > 0.05).

CONCLUSIONS

This study showed that gradually lowering DNa could bring a significant reduction in pre-dialysis IDWG, BP, and ECW without increased adverse events. Large and crossover designed study will be needed to demonstrate the clear causal relationship.

Sodium balance in maintenance hemodialysis

Sodium is the principal solute in the extracellular compartment and the major component of serum osmolality. In normal persons in the steady state, sodium homeostasis is achieved by a balance between the dietary intake and the urinary output of sodium, whereas in intermittent hemodialysis patients, sodium balance depends on dietary intake and sodium removal during hemodialysis. Thus, the main goal of hemodialysis is to remove precisely the amount of sodium that has accumulated during the interdialytic period. Sodium removal during hemodialysis occurs via convective (~78%) and diffusive losses (~22%) between dialysate and plasma sodium concentration. The latter (the sodium gradient) is an important factor in the 'fine tuning' of sodium balance during intermittent hemodialysis. Most use fixed dialysate sodium concentrations, but each patient has his/her own plasma sodium concentrations pre-hemodialysis, which are quite reproducible and stable in the long-term. Thus, in many patients, a fixed dialysate sodium concentration will cause a persistent positive sodium balance during dialysis, which could possibly cause increased thirst, interdialytic weight gain, and mortality. Several methods will be discussed to reduce positive sodium balance, including sodium alignment.

Blood pressure and blood volume: acute and chronic considerations in hemodialysis

Hypertension is highly prevalent yet poorly controlled in the majority of dialysis patients and represents a significant burden of disease, with rates of morbidity and mortality greater than those in the general population. In dialysis, blood volume plays a critical role in the pathogenesis of hypertension, with expansion of extracellular volume increasingly recognized as an independent risk factor for morbidity and mortality. Within the current paradigm of dialysis prescription the majority of patients remain chronically volume expanded. However, management of blood pressure and volume state is difficult for clinicians with a paucity of randomized evidence adding to the complexity of nonlinear morbidity and mortality associations. With dialysis itself as a significant cardiac stressor, control of volume state is critical to minimize intradialytic hemodynamic instability, aid in preservation of cardiac anatomy and prevent progression to cardiovascular morbidity and mortality. This review explores the relationship of blood volume to blood pressure and potential targets for management in this at risk population.

Absolute interdialytic weight gain is more important than percent weight gain for intradialytic hypotension in heavy patients

AIM

Few published reports have mentioned the difference between absolute interdialytic weight gain (IDWG) and IDWG/DW (IDWG%), and subsequent effects on daily dialysis. The aim of present study was to evaluate the difference between absolute IDWG and IDWG% in new haemodialysis patients.

METHOD

We retrospectively reviewed the records of 255 patients who recently received conventional haemodialysis for at least 1 year at the same centre from 1997 to 2008. The first 4 weeks after starting haemodialysis was defined as the pre-study period. Data were collected for 5-56 weeks.

RESULTS

IDWG% value remained relatively constant in the first year of haemodialysis despite most patients having certain residual renal function. For haemodialysis outcomes, both absolute IDWG and IDWG% were significantly correlated with intradialytic hypotension (IDH) in men and heavy women. After dividing patients into four strata, which according to the gender and the median dry weight, stepwise multivariate linear regression analysis showed that absolute IDWG, rather than IDWG%, was an independent risk factor for IDH in heavy men (Beta = 0.585, P < 0.001) and heavy women (Beta= 0.458, P < 0.001).

CONCLUSIONS

Absolute IDWG, rather than IDWG%, is an independent risk factor for IDH in heavy haemodialysis patients. Therefore, higher absolute IDWG needs to be strictly controlled despite the corresponding IDWG% possibly being relatively small in heavy haemodialysis patients.

Epidemiology of interdialytic ambulatory hypertension and the role of volume excess

BACKGROUND

The epidemiology of hypertension among hemodialysis (HD) patients is difficult to describe accurately because of difficulties in the assessment of blood pressure (BP).

METHODS

Using 44-hour interdialytic ambulatory BP measurements, we describe the epidemiology of hypertension in a cohort of 369 patients. To seek correlates of hypertension control, antihypertensive agents were withdrawn among patients with controlled hypertension and ambulatory BP monitoring was repeated.

RESULTS

Hypertension (defined as an average ambulatory systolic BP ≥135 mm Hg or diastolic BP ≥85 mm Hg, or the use of antihypertensive medications) was prevalent in 82% of the patients and independently associated with epoetin use, lower body mass index and fewer years on dialysis. Although 89% of the patients were being treated, hypertension was controlled adequately in only 38%. Poor control was independently associated with greater antihypertensive drug use. Inferior vena cava (IVC) diameter in expiration was associated with increased risk of poorly controlled hypertension both in cross-sectional analysis and after withdrawal of antihypertensive drugs.

CONCLUSIONS

Interdialytic hypertension is highly prevalent and difficult to control among HD patients. End-expiration IVC diameter is associated with poor control of hypertension in cross-sectional analyses as well as after washout of antihypertensive drugs. Among HD patients, an attractive target for improving hypertension control appears to be the reduction of extracellular fluid volume.

Hypertension in small animal kidney disease

Kidney disease is commonly associated with hypertension in dogs, cats and other species. There are multiple mechanisms underlying the development of renal hypertension including sodium retention, activation of the renin-angiotensin system and sympathetic nerve stimulation. The relative importance of these and other mechanisms may vary both between species and according to the type of kidney disease that is present. Consideration of underlying disease mechanisms may aid in the rational choice of therapy in hypertensive patients.

The growing problem of intradialytic hypertension

Intradialytic hypertension is not a rare complication of dialysis, with a prevalence of 5-15% among hemodialysis patients, and it seems to be associated with adverse outcomes. This complex phenomenon is not well understood, and many uncertainties exist regarding its pathophysiologic mechanisms and appropriate treatment strategies. Mechanisms that might be involved in the pathogenesis of intradialytic hypertension include extracellular volume overload, increased cardiac output, changes in electrolyte levels (particularly sodium), activation of the renin-angiotensin-aldosterone system, overactivity of the sympathetic nervous system, and endothelial cell dysfunction. Most current treatment strategies are based only on expert opinion and not on the results of randomized clinical trials, as very little data on the therapy of intradialytic hypertension are available. The most important treatment is adequate sodium and water removal, but reducing sympathetic hyperactivity and reducing endothelin-1 levels should also be considered. Well-designed, randomized clinical trials are urgently needed to better understand the pathophysiologic mechanisms of this complex phenomenon and to improve its diagnosis, prognosis and treatment.

The internist's role in treating hypertension in hemodialysis patients

Hypertension in hemodialysis patients is typically treated with a combination of volume removal with dialysis--although limited by current dialysis paradigms--and hypertension medications. Unfortunately, most patients treated in this manner remain hypertensive. This contrasts with superior results obtained in clinical studies in which salt restriction and augmented dialytic volume removal normalized blood pressure without requiring medicines. These results are consistent with the role of excess volume as the main etiology of hypertension in end-stage renal disease (ESRD). Interdialytic blood pressure is now recognized as important to patient prognosis. These measurements are frequently obtained by internists at office visits. Internists and nephrologists should address both peri-dialysis and interdialysis hypertension in a collaborative manner. This strategy should focus on, as much as reasonably possible, salt restriction and dialytic volume removal rather than hypertension medicines.

Dry-weight reduction in hypertensive hemodialysis patients (DRIP): a randomized, controlled trial

Volume excess is thought to be important in the pathogenesis of hypertension among hemodialysis patients. To determine whether additional volume reduction will result in improvement in blood pressure (BP) among hypertensive patients on hemodialysis and to evaluate the time course of this response, we randomly assigned long-term hypertensive hemodialysis patients to ultrafiltration or control groups. The additional ultrafiltration group (n=100) had the dry weight probed without increasing time or duration of dialysis, whereas the control group (n=50) only had physician visits. The primary outcome was change in systolic interdialytic ambulatory BP. Postdialysis weight was reduced by 0.9 kg at 4 weeks and resulted in -6.9 mm Hg (95% CI: -12.4 to -1.3 mm Hg; P=0.016) change in systolic BP and -3.1 mm Hg (95% CI: -6.2 to -0.02 mm Hg; P=0.048) change in diastolic BP. At 8 weeks, dry weight was reduced 1 kg, systolic BP changed -6.6 mm Hg (95% CI: -12.2 to -1.0 mm Hg; P=0.021), and diastolic BP changed -3.3 mm Hg (95% CI: -6.4 to -0.2 mm Hg; P=0.037) from baseline. The Mantel-Hanzel combined odds ratio for systolic BP reduction of > or =10 mm Hg was 2.24 (95% CI: 1.32 to 3.81; P=0.003). There was no deterioration seen in any domain of the kidney disease quality of life health survey despite an increase in intradialytic signs and symptoms of hypotension. The reduction of dry weight is a simple, efficacious, and well-tolerated maneuver to improve BP control in hypertensive hemodialysis patients. Long-term control of BP will depend on continued assessment and maintenance of dry weight.

The advantages and challenges of increasing the duration and frequency of maintenance dialysis sessions

The duration and frequency of hemodialysis was determined empirically when this therapy first came into use, and treatment was commonly three 8 h sessions per week by the end of the 1960s. Subsequently, however, the growing number of patients who required this therapy had to be reconciled with the shortage of equipment; therefore, dialysis time was decreased to three 4 h sessions per week. At the same time, on the basis of data from the first randomized controlled trial of dialysis -- the National Cooperative Dialysis Study -- Kt/V(urea) was devised as the optimum measure of dialysis adequacy. Nowadays, although Kt/V(urea) targets are fulfilled in an increasing number of patients, observational studies show that individuals on hemodialysis continue to experience a high rate of complications, including hypertension, left ventricular hypertrophy, cardiac failure, hyperphosphatemia, malnutrition and death. Although no randomized controlled trial has yet been published, observational data indicate that increasing hemodialysis time and/or frequency improves a number of these complications, especially the death rate. This Review outlines the advantages of longer and/or more frequent dialysis sessions and highlights the barriers to adoption of such regimens, which largely relate to economics, patient willingness, and organization of dialysis units.

Why is there significant overlap in volume status between hypertensive and normotensive patients on dialysis?

BACKGROUND/AIM

Volume overload is believed to play a pivotal role in the pathogenesis of hypertension in dialysis patients. Although the extracellular water (ECW) content in hypertensive dialysis patients was significantly higher than in normotensive dialysis patients on the whole, there was considerable overlap in ECW between the two groups. Little is known about the hemodynamic characteristics in subgroups of patients with normotension but a high volume (HV) status or with hypertension but a normal volume (NV) status. We investigate the overlap in ECW between controlled and uncontrolled hypertension in dialysis patients.

METHODS

Fifty-two patients (mean age 62 years, 26 males and 26 females) on peritoneal dialysis were enrolled into this study. The ECW was assessed by bioimpedance analysis and normalized by individual height in meters (NECW). The mean value of NECW in both sexes was arbitrarily set to define NV status (lower than mean value) or HV status (higher than mean value). All patients were thus divided into four subgroups: controlled hypertension with NV (CHT-NV), controlled hypertension with HV (CHT-HV), uncontrolled hypertension with NV (UHT-NV) and uncontrolled hypertension with HV (UHT-HV). The stroke volume, cardiac output and total peripheral resistance were echocardiographically measured and their respective indices were calculated.

RESULTS

There were 12 (23%), 8 (15%), 14 (27%) and 18 (35%) patients in the CHT-NV, CHT-HV, UHT-NV and UHT-HV subgroups, respectively. The four subgroups were matched for sex, diabetes and age. The NECW in the CHT-HV group was higher than that in CHT-NV and UHT-NV groups (p < 0.01), but was comparable with that in the UHT-HV group. The stroke volume and cardiac output indices in the CHT-HV group were not significantly different from those in the CHT-NV and UHT-NV groups. The total peripheral resistance index in the CHT-HV group was lower than that in UHT-NV and CHT-NV groups (p < 0.05), but was comparable to that in the UHT-HV group. There was no difference in heart rate among the four groups.

CONCLUSIONS

The overlap in ECW between controlled hypertension and uncontrolled hypertension in dialysis patients was related to a significant difference in total peripheral resistance index, but not to significant differences in stroke volume and cardiac output indices. The CHT-HV patients were characterized by lower total peripheral resistance indices.

Prevalence and determinants of hypertension in chronic hemodialysis patients in Japan

Hypertension is common in chronic hemodialysis (HD) patients. However, its prevalence and determinants have not been studied in a large HD population. We analyzed the database of the Japanese Society for Dialysis Therapy (JSDT) registry, which conducts an annual survey of chronic dialysis patients throughout Japan. We compiled those who were on HD three-times per week and aged 20 years and over at the end of 2000 (JSDT standard analysis file 001). Hypertension was defined as predialysis systolic blood pressure (SBP) > or =140 mm Hg or predialysis diastolic blood pressure (DBP) > or =90 mm Hg. Adjusted odds ratios (95% confidence interval) for the determinants of hypertension were calculated by the multivariate logistic regression analysis. A total of 65 393 people (men, 60.2%; mean age +/- SD, 60.9 +/- 12.8 years; and mean duration of HD +/- SD, 95.3 +/- 74.0 months) were studied. Mean +/- SD levels of SBP and DBP were 154.9 +/- 23.8 mm Hg and 80.5 +/- 13.7 mm Hg before the HD session. Hypertension was noted in 77.5% of patients. Prescription of antihypertensive drugs and erythropoietin was made to 60.7% and 82.0% of patients, respectively. Both SBP and DBP were higher in those who were prescribed antihypertensive drugs (mean, 160.4/81.9 mm Hg), than those without drugs (mean, 146.9/78.5 mm Hg) (in both cases P < 0.0001). Hypertension was positively associated with men (adjusted odds ratio (OR), 1.258; 95% confidence interval (CI), 1.188-1.333; P < 0.0001), age (OR, 1.004; CI, 1.001-1.006; P < 0.01), duration of HD (OR, 0.769; CI, 0.728-0.812; P < 0.0001), serum albumin (OR, 1.369; CI, 1.286-1.458; P < 0.0001), and change in body weight by dialysis session (DeltaBW) (OR, 1.176; CI, 1.159-1.194; P < 0.0001), and was negatively associated with Kt/V (OR, 0.600; CI, 0.543-0.664; P < 0.0001), and hematocrit (OR, 0.964; CI, 0.959-0.970; P < 0.0001). The distribution of DeltaBW was normal in shape and in about 22% of patients the range was from 4.0% to 4.9%. There was a significant positive relationship between the prevalence of hypertension and DeltaBW (R(2) = 0.8549). The higher the DeltaBW, the more the prescription rate of antihypertensive drugs increased (R(2) = 0.9102). Results showed that the prevalence of hypertension was significantly associated with volume excess and serum levels of albumin, calcium, and phosphorous in chronic HD patients. Despite the high prescription rate of antihypertensive drugs, control of blood pressure remains unsatisfactory.