Association of intradialytic blood pressure changes with hospitalization and mortality rates in prevalent ESRD patients

Near-term prediction of sudden cardiac death in older hemodialysis patients using electronic health records

BACKGROUND AND OBJECTIVES

Sudden cardiac death is the most common cause of death among individuals undergoing hemodialysis. The epidemiology of sudden cardiac death has been well studied, and efforts are shifting to risk assessment. This study aimed to test whether assessment of acute changes during hemodialysis that are captured in electronic health records improved risk assessment.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Data were collected from all hemodialysis sessions of patients 66 years and older receiving hemodialysis from a large national dialysis provider between 2004 and 2008. The primary outcome of interest was sudden cardiac death the day of or day after a dialysis session. This study used data from 2004 to 2006 as the training set and data from 2007 to 2008 as the validation set. The machine learning algorithm, Random Forests, was used to derive the prediction model.

RESULTS

In 22 million sessions, 898 people between 2004 and 2006 and 826 people between 2007 and 2008 died on the day of or day after a dialysis session that was serving as a training or test data session, respectively. A reasonably strong predictor was derived using just predialysis information (concordance statistic=0.782), which showed modest but significant improvement after inclusion of postdialysis information (concordance statistic=0.799, P<0.001). However, risk prediction decreased the farther out that it was forecasted (up to 1 year), and postdialytic information became less important.

CONCLUSION

Subtle changes in the experience of hemodialysis aid in the assessment of sudden cardiac death and are captured by modern electronic health records. The collected data are better for the assessment of near-term risk as opposed to longer-term risk.

Hemodynamic and pathophysiological characteristics of intradialytic blood pressure elevation in patients with end-stage renal disease

An increase in systolic blood pressure (SBP) after hemodialysis (intradialytic-HTN) is associated with adverse outcomes in patients on regular hemodialysis. However, the hemodynamic and Doppler echocardiographic characteristics of intradialytic-HTN and its impact on clinical outcomes are unclear. A retrospective analysis of 84 patients (45 men, 70±9 years) stratified into three groups on the basis of SBP response from pre- to post-hemodialysis: GHTN (intradialytic-HTN, SBP increase 10 mm Hg), GDROP<15 mm Hg (SBP drop <15 mm Hg), and GDROP15 mm Hg (SBP drop 15 mm Hg). Hemodynamic and echocardiographic assessments were performed pre- and post-hemodialysis, and patients were followed for 41±17 months. GHTN had higher blood glucose and lower baseline SBP, serum potassium and total cholesterol. Cardiothoracic ratio was smaller, and peak early diastolic mitral annular velocity (E') was lower in GHTN. During hemodialysis, SBP and diastolic blood pressure increased only in GHTN. After hemodialysis, left ventricular (LV) filling pressure (E/E' ratio) decreased only in GDROP15 mm Hg, resulting in a higher E/E' ratio in GHTN than GDROP15 mm Hg. Multivariate logistic regression analysis revealed a positive correlation between blood glucose and intradialytic-HTN, whereas cardiothoracic ratio, pre-hemodialysis SBP and the change in E/E' ratio with hemodialysis were negatively related to intradialytic-HTN. During follow-up, GHTN had more cardiovascular deaths than GDROP15 mm Hg (P=0.03). Multivariate Cox regression analysis showed that lower serum potassium and previous coronary artery disease, but not intradialytic-HTN, were associated with cardiovascular deaths. A higher LV afterload and elevated filling pressures after hemodialysis, indicative of increased cardiovascular stiffening and impaired diastolic filling, may contribute in part to an increased cardiovascular burden in patients with intradialytic-HTN.

A comparative effectiveness research study of the change in blood pressure during hemodialysis treatment and survival

It is not clear to what extent changes in blood pressure (BP) during hemodialysis affect or predict survival. Studying comparative outcomes of BP changes during hemodialysis can have major clinical implications including the impact on management strategies in hemodialysis patients. Here we undertook a retrospective cohort study of 113,255 hemodialysis patients over a 5 year period to evaluate an association between change in BP during hemodialysis and mortality. The change in BP was defined as post- minus pre-hemodialysis BP and mean of BP change values during the hemodialysis session was used as a mortality predictor. The patients averaged 61 years old and consisted of 45% women, 32% African-Americans and 58% diabetics. Over a median follow-up of 2.2 years, a total of 53,461 (47.2%) all-cause and 21,548 (25.7%) cardiovascular deaths occurred. In fully adjusted Cox regression model with restricted cubic splines, there was a U-shaped association between change systolic BP and all-cause mortality. Post-dialytic drops in systolic BP between −30 to 0 mmHg were associated with greater survival, but large decreases of systolic BP (more than −30 mmHg) and any increase in systolic BP (over 0 mmHg) were related to increased mortality. Peak survival was found at a change in systolic BP of −14 mmHg. The U-shaped association was also found for cardiovascular mortality. Thus, modest declines in BP after hemodialysis are associated with the greatest survival, whereas any rise or large decline in BP is associated with worsened survival.

Association of intradialytic blood pressure variability with increased all-cause and cardiovascular mortality in patients treated with long-term hemodialysis

BACKGROUND

Blood pressure is known to fluctuate widely during hemodialysis; however, little is known about the association between intradialytic blood pressure variability and outcomes.

STUDY DESIGN

Retrospective observational cohort.

SETTING & PARTICIPANTS

A random sample of 6,393 adult, thrice-weekly, in-center, maintenance hemodialysis patients dialyzing at 1,026 dialysis units within a single large dialysis organization.

PREDICTOR

Intradialytic systolic blood pressure (SBP) variability. This was calculated using a mixed linear effects model. Peridialytic SBP phenomena were defined as starting SBP (regression intercept), systematic change in SBP over the course of dialysis (2 regression slopes), and random intradialytic SBP variability (absolute regression residual).

OUTCOMES

All-cause and cardiovascular mortality.

MEASUREMENTS

SBPs (n = 631,922) measured during hemodialysis treatments (n = 78,961) during the first 30 days in the study. Outcome data were obtained from the dialysis unit electronic medical record and were considered beginning on day 31.

RESULTS

High (ie, greater than the median) versus low SBP variability was associated with greater risk of all-cause mortality (adjusted HR, 1.26; 95% CI, 1.08-1.47). The association between high SBP variability and cardiovascular mortality was even more potent (adjusted HR, 1.32; 95% CI, 1.01-1.72). A dose-response trend was observed across quartiles of SBP variability for both all-cause (P = 0.001) and cardiovascular (P = 0.04) mortality.

LIMITATIONS

Inclusion of patients from a single large dialysis organization, over-representation of African Americans and patients with diabetes and heart failure, and lack of standardized SBP measurements.

CONCLUSIONS

Greater intradialytic SBP variability is associated independently with increased all-cause and cardiovascular mortality. Further prospective studies are needed to confirm findings and identify means of reducing SBP variability to facilitate randomized study.

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.

Measures of blood pressure and cognition in dialysis patients

There are few reports on the relationship of blood pressure with cognitive function in maintenance dialysis patients. The Cognition and Dialysis Study is an ongoing investigation of cognitive function and its risk factors in six Boston area hemodialysis units. In this analysis, we evaluated the relationship between different domains of cognitive function with systolic and diastolic blood pressure, pulse pressure, and intradialytic changes in systolic blood pressure, using univariate and multivariable linear regression models adjusted for age, sex, race, education, and primary cause of end-stage renal disease. Among 314 participants, mean age was 63 years; 47% were female, 22% were African American, and 48% had diabetes. The mean (SD) of systolic blood pressure, diastolic blood pressure, pulse pressure, and intradialytic change in systolic blood pressure were 141 (21), 73 (12), 68 (15), and -10 (24) mmHg, respectively. In univariate analyses, the performance on cognitive tests primarily assessing executive function and processing speeds was worse among participants with lower diastolic blood pressure and higher pulse pressure. These relationships were not statistically significant, however, in multivariable analyses. There was no association between cognitive function and systolic blood pressure or intradialytic change in systolic blood pressure in either univariate or multivariable analyses. We found no association between different measures of blood pressure and cognitive function in cross-sectional analysis. Longitudinal studies are needed to confirm these results.

Probing the mechanisms of intradialytic hypertension: a pilot study targeting endothelial cell dysfunction

BACKGROUND AND OBJECTIVES

Intradialytic hypertension may be caused by an impaired endothelial cell response to hemodialysis. Carvedilol has been shown to improve endothelial cell function in vivo and to block endothelin-1 release in vitro. This study hypothesized that carvedilol would improve endothelial cell function and reduce the occurrence of intradialytic hypertension.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A prospective 12-week pilot study of carvedilol titrated to 50 mg twice daily was performed among 25 hemodialysis participants with intradialytic hypertension. Each patient served as his or her own control. Paired tests were used to analyze changes in BP and endothelial cell function--assessed by flow-mediated vasodilation, endothelial progenitor cells (aldehyde dehydrogenase bright activity and CD34(+)CD133(+)), asymmetric dimethylarginine, and endothelin-1--from baseline to study end.

RESULTS

Flow-mediated vasodilation was significantly improved with carvedilol (from 1.03% to 1.40%, P=0.02). There was no significant change in endothelial progenitor cells, endothelin-1, or asymmetric dimethylarginine. Although prehemodialysis systolic BP was unchanged (144-146 mmHg, P=0.5), posthemodialysis systolic BP, 44-hour ambulatory systolic BP, and the frequency of intradialytic hypertension decreased with carvedilol (159-142 mmHg, P<0.001; 155-148 mmHg, P=0.05; and 77% [4.6 of 6] to 28% [1.7 of 6], P<0.001, respectively).

CONCLUSIONS

Among hemodialysis participants with intradialytic hypertension, targeting endothelial cell dysfunction with carvedilol was associated with modest improvements in endothelial function, improved intradialytic and interdialytic BP, and reduced frequency of intradialytic hypertension. Randomized controlled trials are required to confirm these findings.

Atrial fibrillation: the beat is faster than the answers

The prevalence of atrial fibrillation is much greater among persons with end-stage renal disease (ESRD) than among the general population. While significant advances have been made recently in the treatment of atrial fibrillation in the general population, we know very little about the treatment of atrial fibrillation among those with ESRD. This Commentary explores gaps in our knowledge of how to treat this vulnerable and sick population.

Sympathetic activation and baroreflex function during intradialytic hypertensive episodes

Background

The mechanisms of intradialytic increases in blood pressure are not well defined. The present study was undertaken to assess the role of autonomic nervous system activation during intradialytic hypertensive episodes.

Methodology/Principal Findings

Continuous interbeat intervals (IBI) and systolic blood pressure (SBP) were monitored during hemodialysis in 108 chronic patients. Intradialytic hypertensive episodes defined as a period of at least 10 mmHg increase in SBP between the beginning and the end of a dialysis session or hypertension resistant to ultrafiltration occurring during or immediately after the dialysis procedure, were detected in 62 out of 113 hemodialysis sessions. SBP variability, IBI variability and baroreceptor sensitivity (BRS) in the low (LF) and high (HF) frequency ranges were assessed using the complex demodulation technique (CDM). Intradialytic hypertensive episodes were associated with an increased (n = 45) or decreased (n = 17) heart rate. The maximal blood pressure was similar in both groups. In patients with increased heart rate the increase in blood pressure was associated with marked increases in SBP and IBI variability, with suppressed BRS indices and enhanced sympatho-vagal balance. In contrast, in those with decreased heart rate, there were no significant changes in the above parameters. End-of- dialysis blood pressure in all sessions associated with hypertensive episode was significantly higher than in those without such episodes. In logistic regression analysis, predialysis BRS in the low frequency range was found to be the main predictor of intradialytic hypertension.

Conclusion/Significance

Our data point to sympathetic overactivity with feed-forward blood pressure enhancement as an important mechanism of intradialytic hypertension in a significant proportion of patients. The triggers of increased sympathetic activity during hemodialysis remain to be determined. Intradialytic hypertensive episodes are associated with higher end-of- dialysis blood pressure, suggesting that intradialytic hypertension may play a role in generation of interdialytic hypertension.

How should we manage adverse intradialytic blood pressure changes?

Variations in intradialytic blood pressure (BP) are a common and predictable occurrence in ESRD patients. These are caused by a decrease in blood volume provoked by ultrafiltration, lack of normal compensatory responses to fluid removal, underlying cardiac disease, and electrolyte changes that may adversely affect cardiovascular function. Intradialytic hypotension is the most frequent complication of the hemodialysis (HD) procedure and is fundamentally a consequence of an ultrafiltration rate that surpasses mechanisms activated to avert a decline in BP. Intradialytic hypertension is a less well-understood problem that has been recently associated with increased mortality. Fundamental patient characteristics and components of the HD procedure are involved in the pathophysiology of intradialytic hypotension and intradialytic hypertension. Correction of patient factors, modulation of HD prescription, and management of pharmacologic agents are the strategies to deal with adverse intradialytic BP changes.

Interdialytic ambulatory blood pressure in patients with intradialytic hypertension

PURPOSE OF REVIEW

Hypertension is common in hemodialysis patients and contributes to this population's high risk for cardiovascular morbidity and mortality. Patients with intradialytic hypertension, or increases in blood pressure during hemodialysis, have been shown to have the highest risk for these outcomes. The purpose of this review is to describe new findings that shed light on the epidemiology and pathophysiology of intradialytic hypertension and discuss how a better understanding of these mechanisms may lead to improved blood pressure management and outcomes in hemodialysis patients.

RECENT FINDINGS

Our laboratory demonstrated that intradialytic hypertension occurs at least sporadically in most hemodialysis patients, but in 25% of patients it occurs in over 31% of their hemodialysis treatments. We also identified that, compared with hemodialysis patients without intradialytic hypertension, those with intradialytic hypertension have worse endothelial cell function and have higher interdialytic ambulatory blood pressure. Pilot study data show that carvedilol reduces the frequency of intradialytic hypertension and improves endothelial cell dysfunction.

SUMMARY

Intradialytic hypertension is associated with increased morbidity and mortality, impaired endothelial cell function, and higher overall blood pressure burden. Further investigation is required to determine whether interventions aimed at preventing or treating intradialytic hypertension improve long-term outcomes.

Postdialysis blood pressure rise predicts long-term outcomes in chronic hemodialysis patients: a four-year prospective observational cohort study

BACKGROUND

The blood pressure (BP) of a proportion of chronic hemodialysis (HD) patients rises after HD. We investigated the influence of postdialysis BP rise on long-term outcomes.

METHODS

A total of 115 prevalent HD patients were enrolled. Because of the fluctuating nature of predialysis and postdialysis BP, systolic BP (SBP) and diastolic BP before and after HD were recorded from 25 consecutive HD sessions during a 2-month period. Patients were followed for 4 years or until death or withdrawal.

RESULTS

Kaplan-Meier estimates revealed that patients with average postdialysis SBP rise of more than 5 mmHg were at the highest risk of both cardiovascular and all-cause mortality as compared to those with an average postdialysis SBP change between -5 to 5 mmHg and those with an average postdialysis SBP drop of more than 5 mmHg. Furthermore, multivariate Cox regression analysis indicated that both postdialysis SBP rise of more than 5 mmHg (HR, 3.925 [95% CI, 1.410-10.846], p = 0.008) and high cardiothoracic (CT) ratio of more than 50% (HR, 7.560 [95% CI, 2.048-27.912], p = 0.002) independently predicted all-cause mortality. We also found that patients with an average postdialysis SBP rise were associated with subclinical volume overload, as evidenced by the significantly higher CT ratio (p = 0.008).

CONCLUSIONS

A postdialysis SBP rise in HD patients independently predicted 4-year cardiovascular and all-cause mortality. Considering postdialysis SBP rise was associated with higher CT ratio, intensive evaluation of cardiac and volume status should be performed in patients with postdialysis SBP rise.

Hypertension and hemodialysis: pathophysiology and outcomes in adult and pediatric populations

Hypertension is prevalent in adult and pediatric end-stage renal disease patients on hemodialysis. Volume overload is a primary factor contributing to hypertension, and attaining true dry weight remains a priority for nephrologists. Other contributing factors to hypertension include activation of the sympathetic and renin-angiotensin-aldosterone systems, endothelial cell dysfunction, arterial stiffness, exposure to hypertensinogenic drugs, and electrolyte imbalances during hemodialysis. Epidemiologic studies in adults show that uncontrolled hypertension results in cardiovascular morbidity, but reveal increased mortality risk at low blood pressure, so that it remains unclear what the target blood pressure should be. Despite the lack of a definitive BP target, gradual dry weight reduction should be the first intervention for BP control. Renin-angiotensin-aldosterone system inhibitors have been shown to improve cardiovascular morbidity and mortality and are recommended as the initial pharmacologic therapy for hypertensive hemodialysis patients. Short-daily or nocturnal hemodialysis are also good therapeutic options for these patients. It is already established that hypertension in pediatric hemodialysis patients is associated with adverse cardiovascular outcomes, and there is emerging evidence that the mechanisms causing hypertension are similar to adults. Hypertension in adult and pediatric hemodialysis patients warrants aggressive management, although clinical trial evidence of a target BP that improves mortality does not currently exist.

Systolic blood pressure and mortality in patients on hemodialysis

Hypertension is extremely common in patients with end-stage renal disease who are receiving hemodialysis, and cardiovascular disease remains the leading cause of death in these patients. However, optimal blood pressure management strategies in this high-risk population are still controversial. This review first discusses the complex association of systolic blood pressure with clinical outcomes in patients on hemodialysis, with a focus on several recent studies. Next, it updates the reader on issues related to optimal timing and methods of blood pressure measurement, appropriate blood pressure targets, and pharmacologic and nonpharmacologic hypertension treatment strategies for patients on hemodialysis.

Intradialytic hypertension and the association with interdialytic ambulatory blood pressure

BACKGROUND AND OBJECTIVES

Increasing BP during maintenance hemodialysis or intradialytic hypertension is associated with increased morbidity and mortality. In hemodialysis patients, ambulatory BP measurements predict adverse cardiovascular outcomes better than in-center measurements. We hypothesized that patients with intradialytic hypertension have higher interdialytic ambulatory systolic BP than those without intradialytic hypertension.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed a case-control study in adult hemodialysis patients. Cases consisted of subjects with intradialytic-hypertension (systolic BP increase ≥10 mmHg from pre- to posthemodialysis in at least four of six treatments), and controls were subjects with ≥10 mmHg decreases from pre- to posthemodialysis in at least four of six treatments. The primary outcome was mean interdialytic 44-hour systolic ambulatory BP.

RESULTS

Fifty subjects with a mean age of 54.5 years were enrolled (25 per group) among whom 80% were men, 86% diabetic, 62% Hispanic, and 38% African American. The mean prehemodialysis systolic BP for the intradialytic-hypertension and control groups were 144.0 and 155.5 mmHg, respectively. Mean posthemodialysis systolic BP was 159.0 and 128.1 mmHg, for the intradialytic-hypertension and control groups, respectively. The mean systolic ambulatory BP was 155.4 and 142.4 mmHg for the intradialytic-hypertension and control groups, respectively (P = 0.005). Both daytime and nocturnal systolic BP were higher among those with intradialytic hypertension as compared with controls. There was no difference in interdialytic weight gain between groups.

CONCLUSIONS

Time-integrated BP burden as measured by 44-hour ambulatory BP is higher in hemodialysis patients with intradialytic hypertension than those without intradialytic hypertension.

UK Renal Registry 13th Annual Report (December 2010): Chapter 11: blood pressure profile of prevalent patients receiving renal replacement therapy in England, Wales and Northern Ireland in 2009: national and centre-specific analyses

BACKGROUND

The UK Renal Registry (UKRR) assesses blood pressure (BP) control annually for patients receiving Renal Replacement Therapy (RRT) at renal centres in England, Wales and Northern Ireland.

METHODS

Patients alive and receiving RRT on 31st December 2009 with a BP reading in either the fourth or third quarter of 2009 were included. Summary statistics were calculated for each renal centre and country.

RESULTS

Data completeness for BP measurements submitted to the UKRR for all modalities improved from the previous year and was better for HD patients (67% for pre-HD measurements) than for PD patients (44%) or transplant recipients (37%). In 2009, the median pre-and post-HD SBP were 142 mmHg and 129 mmHg respectively. The median SBP of patients on PD was 137 mmHg. Transplant recipients had a median SBP of 134 mmHg. Median DBP were 74 mmHg (pre-HD), 68 mmHg (post-HD), 79 mmHg (PD) and 79 mmHg (transplant). Only 26.7% of PD patients achieved the Renal Association guideline of SBP <130 mmHg and DBP <80 mmHg. Amongst transplant patients, 27.2% achieved the Renal Association guideline of SBP <130 mmHg and DBP <80 mmHg.

CONCLUSION

In 2009 there continued to be significant variation in the achievement of BP standards between UK renal centres.

A model of systolic blood pressure during the course of dialysis and clinical factors associated with various blood pressure behaviors

BACKGROUND

Little is known about the behavior of systolic blood pressure (SBP) during hemodialysis.

STUDY DESIGN

Prospective observational cohort.

SETTING & PARTICIPANTS

218 prevalent hemodialysis patients treated at 5 participating DaVita Dialysis units.

PREDICTORS

Clinical variables that may plausibly influence the behavior of SBP during the course of hemodialysis sessions.

OUTCOMES

SBP at the onset of dialysis and its rate of change (slope) over the first 25% and latter 75% of the treatment interval.

MEASUREMENTS

SBPs measured and recorded per clinical protocol during the first 30 days of study (median, 11 treatments/patient; SBP measured at 30-minute intervals).

RESULTS

Intradialytic SBP behavior is well characterized by a 2-slope linear spline model, which describes SBP at time zero, a rapid decrease during the first 25% of the treatment (early), and a more gradual decrease thereafter (late). Higher ultrafiltration volume and rate each are associated with greater SBP at the start of dialysis and more rapid early and late SBP decreases. Use of a higher number of antihypertensives was associated with greater time zero SBP. Calcium acetate use is associated with high SBP at the start of hemodialysis and a more pronounced decrease during the early and late parts of treatment.

LIMITATIONS

Over-representation of blacks and patients with congestive heart failure; observational design; use of clinically measured blood pressures.

CONCLUSIONS

Intradialytic SBP can be characterized using 3 parameters: value at the start of dialysis and slopes during the first 25% and latter 75% of treatment. Practices related to fluid management, antihypertensive use, and metabolic bone disease control are associated with blood pressure behavior during dialysis. Further work is needed to confirm findings and measure associations between various aspects of intradialytic blood pressure behavior and clinical outcomes.

Intradialytic hypertension and its association with endothelial cell dysfunction

BACKGROUND AND OBJECTIVES

Intradialytic hypertension is associated with adverse outcomes, yet the mechanism is uncertain. Patients with intradialytic hypertension exhibit imbalances in endothelial-derived vasoregulators nitric oxide and endothelin-1, indirectly suggesting endothelial cell dysfunction. We hypothesized that intradialytic hypertension is associated in vivo with endothelial cell dysfunction, a novel predictor of adverse cardiovascular outcomes.

DESIGN, SETTINGS, PARTICIPANTS, & MEASUREMENTS

We performed a case-control cohort study including 25 hemodialysis (HD) subjects without (controls) and 25 with intradialytic hypertension (an increase in systolic BP pre- to postdialysis ≥10 mmHg ≥4/6 consecutive HD sessions). The primary outcome was peripheral blood endothelial progenitor cells (EPCs) assessed by aldehyde dehydrogenase activity (ALDH(br)) and cell surface marker expression (CD34(+)CD133(+)). We also assessed endothelial function by ultrasonographic measurement of brachial artery flow-mediated vasodilation (FMD) normalized for shear stress. Parametric and nonparametric t tests were used to compare EPCs, FMD, and BP.

RESULTS

Baseline characteristics and comorbidities were similar between groups. Compared with controls, 2-week average predialysis systolic BP was lower among subjects with intradialytic hypertension (144.0 versus 155.5 mmHg), but postdialysis systolic BP was significantly higher (159.0 versus 128.1 mmHg). Endothelial cell function was impaired among subjects with intradialytic hypertension as measured by decreased median ALDH(br) cells and decreased CD34(+)CD133(+) cells (ALDH(br), 0.034% versus 0.053%; CD34(+)CD133(+), 0.033% versus 0.059%). FMD was lower among subjects with intradialytic hypertension (1.03% versus 1.67%).

CONCLUSIONS

Intradialytic hypertension is associated with endothelial cell dysfunction. We propose that endothelial cell dysfunction may partially explain the higher event rates observed in these patients.

Modeled urea distribution volume and mortality in the HEMO Study

BACKGROUND AND OBJECTIVES

In the Hemodialysis (HEMO) Study, observed small decreases in achieved equilibrated Kt/V(urea) were noncausally associated with markedly increased mortality. Here we examine the association of mortality with modeled volume (V(m)), the denominator of equilibrated Kt/V(urea).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Parameters derived from modeled urea kinetics (including V(m)) and blood pressure (BP) were obtained monthly in 1846 patients. Case mix-adjusted time-dependent Cox regressions were used to relate the relative mortality hazard at each time point to V(m) and to the change in V(m) over the preceding 6 months. Mixed effects models were used to relate V(m) to changes in intradialytic systolic BP and to other factors at each follow-up visit.

RESULTS

Mortality was associated with V(m) and change in V(m) over the preceding 6 months. The association between change in V(m) and mortality was independent of vascular access complications. In contrast, mortality was inversely associated with V calculated from anthropometric measurements (V(ant)). In case mix-adjusted analysis using V(m) as a time-dependent covariate, the association of mortality with V(m) strengthened after statistical adjustment for V(ant). After adjustment for V(ant), higher V(m) was associated with slightly smaller reductions in intradialytic systolic BP and with risk factors for mortality including recent hospitalization and reductions in serum albumin concentration and body weight.

CONCLUSIONS

An increase in V(m) is a marker for illness and mortality risk in hemodialysis patients.

Intra-dialytic hypotension and blood volume and blood temperature monitoring

Intra-dialytic hypotension (IDH) is a common problem affecting haemodialysis patients. Its aetiology is complex and influenced by multiple patient and dialysis factors. IDH occurs when the normal cardiovascular response cannot compensate for volume loss associated with ultrafiltration, and is exacerbated by a myriad of factors including intra-dialytic fluid gains, cardiovascular disease, antihypertensive medications and the physiological demands placed on patients by conventional haemodialysis. The use of blood volume monitoring and blood temperature monitoring technologies is advocated as a tool to predict and therefore prevent episodes of IDH. We review the clinical utility of these technologies and summarize the current evidence of their effect on reducing the incidence of IDH in haemodialysis population.

Blood pressure management in hemodialysis: what have we learned?

PURPOSE OF REVIEW

To review recent developments in the field of hypertension in hemodialysis patients.

RECENT FINDINGS

Despite the fact that hypertension is the most common complication of end-stage kidney disease, no evidence-based blood pressure (BP) targets exist for hemodialysis patients. There is growing evidence that outcomes are better predicted by out-of-office BP values, such as home or ambulatory BP monitoring. Intradialytic hypertension is associated with increased risk of death or hospitalization, and is probably mediated by volume overload. BP management should focus on volume control: dry weight 'probing' is well tolerated and effective in lowering BP, as are other strategies that minimize expansion of the extracellular fluid volume, such as avoidance of hypernatric dialysate. We discuss each of these issues in our review.

SUMMARY

Modest advances in the understanding of hypertension have occurred in the past 2 years. Clinical trials that focus on BP targets and treatment choices are essential to guide future practice.

Hypertension in patients with chronic kidney disease

Hypertension is very common in patients with chronic kidney disease (CKD); it causes early loss of kidney function and accelerated cardiovascular morbidity and mortality. African American patients with hypertension and genetic disposition are at an even higher risk for renal disease and ultimately renal failure. Hypertensive patients with CKD should aim for stringent blood pressure (BP) control (target < 130/80 mm Hg) requiring more than one drug with renin-angiotensin-aldosterone system blockade as a component of therapy targeting both hyper-tension and proteinuria. Management of hypertension in the dialysis population should focus on ambulatory measurements of BP and the use of longer-acting antihypertensive drugs, with their dosage and timing adjusted according to their dialytic clearances. Hypertension is also common among kidney transplant recipients and contributes to graft loss and premature death. The target BP in transplant recipients is the same as in the CKD population, with no preference for one drug group over another. Unless contraindicated, angiotensin-converting enzyme inhibitors remain the drugs of choice for hypertension in patients with autosomal-dominant polycystic kidney disease, in whom diastolic cardiac dysfunction is a prominent feature.

Variability--the drama of the circulation

The two most common vital signs, ie, pulse and blood pressure (BP), are obtained to seek guidance in clinical management of patients in virtually all primary care practices. Even a cursory glance at their values, whether it is within a person over time or between patients on a particular day, reflects an amazing degree of variability. In this brief editorial we provide a focused review of the assessment and the importance of variability in within-patient heart rate and BP and conclude with a few thoughts about the discordance in significance attached to these ubiquitous clinical measures.

Antihypertensive agents in hemodialysis patients: a current perspective

Hypertension affects most hemodialysis patients and is often poorly controlled. Adequate control of blood pressure is difficult with conventional hemodialysis alone but is important to improve cardiovascular outcomes. Nonpharmacologic interventions to improve blood pressure include educating patients about limiting sodium intake, ensuring adequate sodium solute removal during hemodialysis, and achieving target "dry weight." However, most patients require a number of antihypertensive medications to achieve an appropriate blood pressure. First-line antihypertensive agents include angiotensin converting enzyme inhibitors and angiotensin receptor blockers given their safety profile and demonstrated benefit on cardiovascular outcomes in clinical trials. beta-blockers and combined alpha- and beta-blockers should also be used in patients with cardiovascular disease or congestive heart failure and may improve outcomes in these populations. Calcium channel blockers and direct vasodilators are also effective for controlling blood pressure. Many blood pressure agents can be dosed once daily and should preferentially be administered at night to control nocturnal blood pressure and minimize intradialytic hypotension. In patients who are noncompliant with therapy, renally eliminated agents (such as lisinopril and atenolol) can be given thrice weekly following hemodialysis. Older antihypertensive agents which require thrice daily dosing ought to be avoided given the high pill burden with these regimens and the concern for noncompliance resulting in rebound hypertension. Newer antihypertensive agents, such as direct renin inhibitors, may provide alternative options to improve blood pressure but require testing for efficacy and safety in hemodialysis patients.

Intradialytic hypertension: a less-recognized cardiovascular complication of hemodialysis

Intradialytic hypertension, defined as an increase in blood pressure during or immediately after hemodialysis that results in postdialysis hypertension, has long been recognized to complicate the hemodialysis procedure, yet often is largely ignored. In light of recent investigations suggesting that intradialytic hypertension is associated with adverse outcomes, this review broadly covers the epidemiologic characteristics, prognostic significance, potential pathogenic mechanisms, prevention, and possible treatment of intradialytic hypertension. Intradialytic hypertension affects up to 15% of hemodialysis patients and occurs more frequently in patients who are older, have lower dry weights, are prescribed more antihypertensive medications, and have lower serum creatinine levels. Recent studies associated intradialytic hypertension independently with higher hospitalization rates and decreased survival. Although the pathophysiologic mechanisms of intradialytic hypertension are uncertain, it likely is multifactorial and includes subclinical volume overload, sympathetic overactivity, activation of the renin-angiotensin system, endothelial cell dysfunction, and specific dialytic techniques. Prevention and treatment of intradialytic hypertension may include careful attention to dry weight, avoidance of dialyzable antihypertensive medications, limiting the use of high-calcium dialysate, achieving adequate sodium solute removal during hemodialysis, and using medications that inhibit the renin-angiotensin-aldosterone system or decrease endothelin 1 levels. In summary, although intradialytic hypertension often is underappreciated, recent studies suggest that it should not be ignored. However, further work is necessary to elucidate the pathophysiologic mechanisms of intradialytic hypertension and its appropriate management and determine whether treatment of intradialytic hypertension can improve clinical outcomes.

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.

Association of blood pressure increases during hemodialysis with 2-year mortality in incident hemodialysis patients: a secondary analysis of the Dialysis Morbidity and Mortality Wave 2 Study

BACKGROUND

Intradialytic increases in blood pressure (BP) can complicate the management of hypertension in hemodialysis (HD) patients. However, the long-term consequences are uncertain. Thus, we sought to determine whether BP increases during HD were associated with greater 2-year mortality in incident HD patients.

STUDY DESIGN

Secondary analysis of a prospective dialysis cohort.

SETTING & PARTICIPANTS

Incident HD patients in the Dialysis Morbidity and Mortality Wave 2 Study.

PREDICTORS

Changes in systolic BP (SBP) during HD (ie, postdialysis SBP -- predialysis SBP), averaged from 3 HD sessions before enrollment.

OUTCOME

Time to 2-year all-cause mortality.

MEASUREMENTS

Cox regression was used to model hazard ratios for mortality associated with changes in SBP during HD while adjusting for demographics, comorbid conditions, interdialytic weight gain, laboratory variables, and antihypertensive agents.

RESULTS

Of 1,748 patients, 12.2% showed greater than 10-mm Hg increases in SBP during HD. In adjusted analyses, every 10-mm Hg increase in SBP during HD was associated independently with a 6% increased hazard of death (hazard ratio, 1.06; 95% confidence interval, 1.01 to 1.11). When also adjusted for diastolic BP and postdialysis SBP, the adjusted hazard of death associated with increasing SBP during HD remained significant (hazard ratio, 1.12; 95% confidence interval, 1.05 to 1.21 per 10-mm Hg increase in SBP during HD). However, in analyses adjusted for predialysis SBP, there was a significant interaction between change in SBP and predialysis SBP. In analyses stratified by predialysis SBP, trends for increased mortality associated with increasing SBP during dialysis were present in patients with predialysis SBP less than 160 mm Hg. However, this relationship was significant only in patients with predialysis SBP less than 120 mm Hg.

LIMITATIONS

Secondary analysis with a limited number of baseline BP measurements and limited information about dialysis prescription.

CONCLUSIONS

Increasing SBP by more than 10 mm Hg during HD occurs in approximately 10% of incident patients, and although increasing SBP during HD was associated with decreased 2-year survival, these findings were limited to patients with predialysis SBP less than 120 mm Hg.

Decreased pulse pressure during hemodialysis is associated with improved 6-month outcomes

Pulse pressure is a well established marker of vascular stiffness and is associated with increased mortality in hemodialysis patients. Here we sought to determine if a decrease in pulse pressure during hemodialysis was associated with improved outcomes using data from 438 hemodialysis patients enrolled in the 6-month Crit-Line Intradialytic Monitoring Benefit Study. The relationship between changes in pulse pressure during dialysis (2-week average) and the primary end point of non-access-related hospitalization and death were adjusted for demographics, comorbidities, medications, and laboratory variables. In the analyses that included both pre- and post-dialysis pulse pressure, higher pre-dialysis and lower post-dialysis pulse pressure were associated with a decreased hazard of the primary end point. Further, every 10 mm Hg decrease in pulse pressure during dialysis was associated with a 20% lower hazard of the primary end point. In separate models that included pulse pressure and the change in pulse pressure during dialysis, neither pre- nor post-dialysis pulse pressure were associated with the primary end point, but each 10 mm Hg decrease in pulse pressure during dialysis was associated with about a 20% lower hazard of the primary end point. Our study found that in prevalent dialysis subjects, a decrease in pulse pressure during dialysis was associated with improved outcomes. Further study is needed to identify how to control pulse pressure to improve outcomes.

Diagnostic utility of blood volume monitoring in hemodialysis patients

BACKGROUND

Assessment of volume state is difficult in hemodialysis patients. Whether continuous blood volume monitoring can improve the assessment of volume state is unclear.

STUDY DESIGN

Diagnostic test study.

SETTINGS & PARTICIPANTS

Asymptomatic long-term hemodialysis patients (n = 150) in 4 university-affiliated hemodialysis units.

INDEX TESTS

Ultrafiltration rate (UFR) divided by postdialysis weight (UFR index), slopes of relative blood volume (RBV), RBV slope corrected for UFR and weight (volume index).

REFERENCE TESTS

Dialysis-related symptoms and echocardiographic signs of volume excess and volume depletion, assessed by using inferior vena cava (IVC) diameter after dialysis and its collapse on inspiration. Volume excess was defined as values in the upper third of IVC diameter or lower third of IVC collapse on inspiration. Volume depletion was defined as values in the lower third of IVC diameter or upper third of IVC collapse on inspiration.

RESULTS

Mean UFR was 8.3 +/- 3.8 (SD) mL/h/kg. Mean RBV slope was -2.32% +/- 1.50%/h. Mean volume index was -0.25% +/- 0.17%/h/mL/h ultrafiltration/kg. Volume index provided the best fit of observed RBV slopes. Volume index was related to dizziness, the need to decrease UFR, and placement in Trendelenburg position. RBV and volume index, but not UFR index, were related to echocardiographic markers of volume excess and depletion. Areas under the receiver operating characteristic curve to predict volume excess were 0.48 (95% confidence interval [CI], 0.33 to 0.63) for UFR index, 0.71 (95% CI, 0.60 to 0.83) for RBV slope, and 0.73 (95% CI, 0.59 to 0.86) for volume index. Areas under the receiver operating characteristic curve to predict volume depletion were 0.56 (95% CI, 0.38 to 0.74) for UFR index, 0.55 (95% CI, 0.38 to 0.72) for RBV slope, and 0.62 (95% CI, 0.48 to 0.76) for volume index.

LIMITATIONS

Dialysis-related symptoms and echocardiographic findings are not validated measures of volume. Our results were not adjusted for demographic or clinical characteristics; performance characteristics of the indices may differ across populations.

CONCLUSIONS

Volume index appears to be a novel marker of volume, but requires validation studies, and its utility needs to be tested in clinical trials.