Peridialytic, Intradialytic, and Interdialytic Blood Pressure Measurement in Hemodialysis Patients

Abstract

Related Article, p. 881 Related Article, p. 881 Among hemodialysis (HD) patients,1Agarwal R. Nissenson A.R. Batlle D. et al.Prevalence, treatment, and control of hypertension in chronic hemodialysis patients in the United States.Am J Med. 2003; 115: 291-297Abstract Full Text Full Text PDF PubMed Scopus (381) Google Scholar hypertension is highly prevalent and frequently uncontrolled. Treatment of HD patients with antihypertensive medications is associated with improved cardiovascular outcomes.2Heerspink H.J. Ninomiya T. Zoungas S. et al.Effect of lowering blood pressure on cardiovascular events and mortality in patients on dialysis: a systematic review and meta-analysis of randomised controlled trials.Lancet. 2009; 373: 1009-1015Abstract Full Text Full Text PDF PubMed Scopus (334) Google Scholar, 3Agarwal R. Sinha A.D. Cardiovascular protection with antihypertensive drugs in dialysis patients: systematic review and meta-analysis.Hypertension. 2009; 53: 860-866Crossref PubMed Scopus (156) Google Scholar Cardiovascular disease is a leading cause of death in HD patients.4Sarnak M.J. Levey A.S. Schoolwerth A.C. et al.Kidney disease as a risk factor for development of cardiovascular disease: a statement from the American Heart Association Councils on Kidney in Cardiovascular Disease, High Blood Pressure Research, Clinical Cardiology, and Epidemiology and Prevention.Circulation. 2003; 108: 2154-2169Crossref PubMed Scopus (2888) Google Scholar Nonetheless, there is no consensus about whether to lower increased blood pressure (BP) in HD patients or the level to which BP should be targeted.5Foley R.N. Agarwal R. Hypertension is harmful to dialysis patients and should be controlled.Semin Dial. 2007; 20: 518-522Crossref PubMed Scopus (14) Google Scholar, 6Agarwal R. Hypertension and survival in chronic hemodialysis patients—past lessons and future opportunities.Kidney Int. 2005; 67: 1-13Crossref PubMed Scopus (139) Google Scholar This is caused in large part by difficulties associated with accurate assessment of BP in HD patients.7Agarwal R. Systolic hypertension in hemodialysis patients.Semin Dial. 2003; 16: 208-213Crossref PubMed Scopus (41) Google Scholar, 8Agarwal R. Peixoto A.J. Santos S.F. et al.Pre and post dialysis blood pressures are imprecise estimates of interdialytic ambulatory blood pressure.Clin J Am Soc Nephrol. 2006; 1: 389-398Crossref PubMed Scopus (178) Google Scholar, 9Li Z. Lacson Jr, E. Lowrie E.G. et al.The epidemiology of systolic blood pressure and death risk in hemodialysis patients.Am J Kidney Dis. 2006; 48: 606-615Abstract Full Text Full Text PDF PubMed Scopus (161) Google Scholar, 10Lacson Jr, E. Lazarus J.M. The association between blood pressure and mortality in ESRD—not different from the general population?.Semin Dial. 2007; 20: 510-517Crossref PubMed Scopus (36) Google Scholar BP measurement among HD patients can be obtained by 3 methods. These methods include peridialytic, intradialytic, and interdialytic measurements. Peridialytic BP measurements form the basis of the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines11National Kidney FoundationK/DOQI Clinical Practice Guidelines for Cardiovascular Disease in Dialysis Patients.Am J Kidney Dis. 2005; 45: S1-S153Google Scholar and are used for management of hypertension in the majority of HD patients today; these are the BP measurements performed by dialysis unit staff shortly before and after the HD session. Thus, peridialytic BP recordings, which are often obtained without attention to method of measurement, have been used in the large cohort studies that have found a reverse epidemiology, in which lower BP has been associated with higher mortality rates in HD patients.6Agarwal R. Hypertension and survival in chronic hemodialysis patients—past lessons and future opportunities.Kidney Int. 2005; 67: 1-13Crossref PubMed Scopus (139) Google Scholar, 12Port F.K. Hulbert-Shearon T.E. Wolfe R.A. et al.Predialysis blood pressure and mortality risk in a national sample of maintenance hemodialysis patients.Am J Kidney Dis. 1999; 33: 507-517Abstract Full Text Full Text PDF PubMed Google Scholar, 13Zager P.G. Nikolic J. Brown R.H. et al.“U” Curve association of blood pressure and mortality in hemodialysis patients.Kidney Int. 1998; 54 ([published erratum appears in Kidney Int. 1998;Oct;54(4):1417]): 561-569Crossref PubMed Scopus (593) Google Scholar Routine peridialytic BP recordings are highly variable and poorly reproducible, whether these assessments are performed in carefully controlled research settings or larger epidemiologic studies.14Agarwal R. Andersen M.J. Bishu K. et al.Home blood pressure monitoring improves the diagnosis of hypertension in hemodialysis patients.Kidney Int. 2006; 69: 900-906Crossref PubMed Scopus (118) Google Scholar, 15Rohrscheib M.R. Myers O.B. Servilla K.S. et al.Age-related blood pressure patterns and blood pressure variability among hemodialysis patients.Clin J Am Soc Nephrol. 2008; 3: 1407-1414Crossref PubMed Scopus (56) Google Scholar Even when assessed using standard measurement methods, peridialytic BP recordings do not correlate well with end-organ damage, such as left ventricular hypertrophy or cardiovascular outcomes.16Agarwal R. Brim N.J. Mahenthiran J. et al.Out-of-hemodialysis-unit blood pressure is a superior determinant of left ventricular hypertrophy.Hypertension. 2006; 47: 62-68Crossref PubMed Scopus (145) Google Scholar, 17Alborzi P. Patel N. Agarwal R. Home blood pressures are of greater prognostic value than hemodialysis unit recordings.Clin J Am Soc Nephrol. 2007; 2: 1228-1234Crossref PubMed Scopus (178) Google Scholar Cohort studies suggest that achieving recommended peridialysis BP targets is associated with increased frequency of intradialytic hypotension.18Davenport A. Cox C. Thuraisingham R. Achieving blood pressure targets during dialysis improves control but increases intradialytic hypotension.Kidney Int. 2007; 73: 759-764Crossref PubMed Scopus (165) Google Scholar Not surprisingly, there is poor agreement between routine peridialytic BP and the gold standard of BP measurement, interdialytic ambulatory BP monitoring.8Agarwal R. Peixoto A.J. Santos S.F. et al.Pre and post dialysis blood pressures are imprecise estimates of interdialytic ambulatory blood pressure.Clin J Am Soc Nephrol. 2006; 1: 389-398Crossref PubMed Scopus (178) Google Scholar The diagnostic performance of peridialytic BP recordings can be improved by consideration of intradialytic recordings.19Agarwal R. Metiku T. Tegegne G.G. et al.Diagnosing hypertension by intradialytic blood pressure recordings.Clin J Am Soc Nephrol. 2008; 3: 1364-1372Crossref PubMed Scopus (67) Google Scholar Intradialytic BP is a recording made during HD, typically every 30 minutes, using an automatic cuff attached to the HD machine. Diagnosing hypertension using ambulatory BP as a gold standard, average intradialytic BP considered together with peridialytic BP has greater diagnostic value compared with peridialytic BP recordings alone.19Agarwal R. Metiku T. Tegegne G.G. et al.Diagnosing hypertension by intradialytic blood pressure recordings.Clin J Am Soc Nephrol. 2008; 3: 1364-1372Crossref PubMed Scopus (67) Google Scholar However, because calculating an average is time consuming and impractical at the bedside, median intradialytic BP (which is an adequate measure for central tendency and is close to the mean in normally distributed data) from a single HD session also appears appropriate for the diagnosis of hypertension. It is possible that intradialytic BP correlates better with ambulatory BP than peridialytic BP because the latter, similar to interdialytic BP, samples the patient during a range of extracellular fluid volume and uremic states, albeit during the condensed time span of the HD session. The third type of BP measurement is interdialytic, which can be obtained using ambulatory BP monitoring or self-measurement by the patient using home BP monitoring.20Peixoto A.J. White W.B. Circadian blood pressure: clinical implications based on the pathophysiology of its variability.Kidney Int. 2007; 71: 855-860Crossref PubMed Scopus (57) Google Scholar, 21Thompson A.M. Pickering T.G. The role of ambulatory blood pressure monitoring in chronic and end-stage renal disease.Kidney Int. 2006; 70: 1000-1007Crossref PubMed Scopus (71) Google Scholar, 22Agarwal R. Role of home blood pressure monitoring in hemodialysis patients.Am J Kidney Dis. 1999; 33: 682-687Abstract Full Text Full Text PDF PubMed Scopus (55) Google Scholar Regardless of the technique of interdialytic BP assessment, these measurements appear to carry greater prognostic information compared with peridialytic recordings.17Alborzi P. Patel N. Agarwal R. Home blood pressures are of greater prognostic value than hemodialysis unit recordings.Clin J Am Soc Nephrol. 2007; 2: 1228-1234Crossref PubMed Scopus (178) Google Scholar For example, interdialytic ambulatory BP is valid23Peixoto A.J. Gray T.A. Crowley S.T. Validation of the SpaceLabs 90207 ambulatory blood pressure device for hemodialysis patients.Blood Press Monit. 1999; 4: 217-221PubMed Google Scholar and reproducible,24Peixoto A.J. Santos S.F. Mendes R.B. et al.Reproducibility of ambulatory blood pressure monitoring in hemodialysis patients.Am J Kidney Dis. 2000; 36: 983-990Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar correlates with echocardiographic evidence of left ventricular hypertrophy,16Agarwal R. Brim N.J. Mahenthiran J. et al.Out-of-hemodialysis-unit blood pressure is a superior determinant of left ventricular hypertrophy.Hypertension. 2006; 47: 62-68Crossref PubMed Scopus (145) Google Scholar and is a predictor of increased mortality in HD patients.17Alborzi P. Patel N. Agarwal R. Home blood pressures are of greater prognostic value than hemodialysis unit recordings.Clin J Am Soc Nephrol. 2007; 2: 1228-1234Crossref PubMed Scopus (178) Google Scholar Similarly, increased home BP has correlated with left ventricular hypertrophy and increased cardiovascular and all-cause mortality in HD patients.16Agarwal R. Brim N.J. Mahenthiran J. et al.Out-of-hemodialysis-unit blood pressure is a superior determinant of left ventricular hypertrophy.Hypertension. 2006; 47: 62-68Crossref PubMed Scopus (145) Google Scholar, 17Alborzi P. Patel N. Agarwal R. Home blood pressures are of greater prognostic value than hemodialysis unit recordings.Clin J Am Soc Nephrol. 2007; 2: 1228-1234Crossref PubMed Scopus (178) Google Scholar The superiority of these methods is not dependent on only their greater number of measurements because interdialytic BP measures retain their correlation with all-cause mortality, even if a smaller number of randomly chosen measurements are analyzed.25Agarwal R. Andersen M.J. Light R.P. Location not quantity of blood pressure measurements predicts mortality in hemodialysis patients.Am J Nephrol. 2007; 28: 210-217Crossref PubMed Scopus (51) Google Scholar It is believed that interdialytic BP measurements are superior because they provide a more accurate reflection of the patient's BP burden over time, and this burden is sampled over the range of extracellular fluid volume and uremic states, from the nadir shortly after an HD session to the zenith just before the next HD session.26Kelley K. Light R.P. Agarwal R. Trended cosinor change model for analyzing hemodynamic rhythm patterns in hemodialysis patients.Hypertension. 2007; 50: 143-150Crossref PubMed Scopus (42) Google Scholar, 27Agarwal R. Light R.P. Chronobiology of arterial hypertension in hemodialysis patients: implications for home blood pressure monitoring.Am J Kidney Dis. 2009; 54: 693-701Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar Ambulatory BP monitoring can be cumbersome for some patients to perform, which is perhaps the main reason that the readily available peridialytic BP is still the primary measure used for diagnosing and treating hypertension in HD patients. However, home BP measurement changes also track well with changes in ambulatory BP recordings; therefore, home BP can be used to make therapeutic decisions.28Agarwal R. Satyan S. Alborzi P. et al.Home blood pressure measurements for managing hypertension in hemodialysis patients.Am J Nephrol. 2009; 30: 126-134Crossref PubMed Scopus (51) Google Scholar In this issue of the American Journal of Kidney Diseases, Inrig et al29Inrig J.K. Patel U.D. Toto R.D. 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.Am J Kidney Dis. 2009; 54: 881-890Abstract Full Text Full Text PDF PubMed Scopus (127) Google Scholar report that increasing peridialytic systolic BP in incident HD patients with normal pre-HD systolic BP is significantly associated with increased mortality at 2 years. This observation comes on the heels of a post hoc analysis of a randomized trial in which Inrig et al reported increased 6-month mortality rates with increasing peridialytic systolic BP.30Inrig J.K. Patel U.D. Gillespie B.S. et al.Relationship between interdialytic weight gain and blood pressure among prevalent hemodialysis patients.Am J Kidney Dis. 2007; 50: 108-118Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar Given that both are observational studies, which do not prove cause and effect, interpretation of these findings requires 2 approaches. The questions we pose are the following: first, if the findings are causally related, why should they be so; and second, if the findings are unrelated, what could underlie the observations. We, like the authors, cannot think of a plausible direct causal link between increasing BP and increased mortality. It thus follows that the observed increase in mortality would not be mitigated if the increase in peridialytic BP were prevented through such measures as predialysis use of antihypertensive medications. If the findings are causally unrelated, there are several possible reasons for this association (Box 1). First, as the authors speculate, increasing BP may be a manifestation of endothelin excess that is associated with endothelial dysfunction and atherosclerosis, which may manifest in the observed increased mortality.31Chou K.J. Lee P.T. Chen C.L. et al.Physiological changes during hemodialysis in patients with intradialysis hypertension.Kidney Int. 2006; 69: 1833-1838Crossref PubMed Scopus (100) Google Scholar Second, the observed increase in mortality was limited to patients with low-normal pre-HD BP who also had increasing peridialytic BP. These patients often are clinically dwindling because of advanced chronic disease. Patients with increasing peridialytic systolic BP are noted by Inrig et al29Inrig J.K. Patel U.D. Toto R.D. 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.Am J Kidney Dis. 2009; 54: 881-890Abstract Full Text Full Text PDF PubMed Scopus (127) Google Scholar to have significantly lower interdialytic weight gain and serum phosphorus levels, consistent with decreased oral intake. Similarly, these patients have significantly lower body mass index and serum creatinine levels, consistent with more wasting than patients without an increase in peridialytic BP. Also, they are noted to have significantly lower serum albumin levels, consistent with more inflammation. Perhaps the increased mortality in this population is caused by advanced chronic illness that is not accounted for in statistical adjustments.32Agarwal R. Exploring the paradoxical relationship of hypertension with mortality in chronic hemodialysis.Hemodial Int. 2004; 8: 207-213Crossref PubMed Scopus (16) Google Scholar Third, patients with normal pre-HD systolic BP also may be more prone to intradialytic hypotension than the rest of the HD population, which might in turn be prevented or treated with hypernatremic dialysate, frequent cessation of ultrafiltration, and saline infusions. These interventions can result in increased post-HD systolic BP and leave the patient volume overloaded, which itself is another potential cause of the observed increased mortality. Unfortunately, intradialytic BP recordings were not available for investigation of intradialytic hypotensive episodes. Fourth, if these patients start HD with normal systolic BP and finish with a higher systolic BP, their systolic BP must necessarily decrease in the interdialytic period to a normal value before their next HD session. This decreasing BP in the interdialytic period is a potential marker of volume excess.33Agarwal R. Volume-associated ambulatory blood pressure patterns in hemodialysis patients.Hypertension. 2009; 54: 241-247Crossref PubMed Scopus (48) Google Scholar Given the study design, we do not have measurements of volume state or level of left ventricular function, either of which can predict mortality.34Satyan S. Light R.P. Agarwal R. Relationships of N-terminal pro-B-natriuretic peptide and cardiac troponin T to left ventricular mass and function and mortality in asymptomatic hemodialysis patients.Am J Kidney Dis. 2007; 50: 1009-1019Abstract Full Text Full Text PDF PubMed Scopus (118) Google Scholar Fifth, we do not know how reproducible the observed increases in peridialytic BP values are because they are from only 3 consecutive HD sessions, and peridialytic BP recordings are prone to high variability.24Peixoto A.J. Santos S.F. Mendes R.B. et al.Reproducibility of ambulatory blood pressure monitoring in hemodialysis patients.Am J Kidney Dis. 2000; 36: 983-990Abstract Full Text Full Text PDF PubMed Scopus (75) Google ScholarBox 1Possible Explanations for the Association Between Increasing Peridialytic BP and Mortality in Patients With Low-Normal Pre-HD Systolic BP1.Increasing BP is a marker of endothelial dysfunction.2.Low pre-HD BP is a marker of advanced chronic illness.3.Low pre-HD BP is a marker of susceptibility to intradialytic hypotension, which, when treated, leads to volume overload.4.Increasing peridialytic BP is itself a marker of volume overload.5.Increasing peridialytic BP is not reproducible within a given patient; therefore, the observed association with mortality is a random event.Abbreviations: BP, blood pressure; HD, hemodialysis. Open table in a new tab Abbreviations: BP, blood pressure; HD, hemodialysis. Not withstanding these limitations, the report by Inrig et al29Inrig J.K. Patel U.D. Toto R.D. 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.Am J Kidney Dis. 2009; 54: 881-890Abstract Full Text Full Text PDF PubMed Scopus (127) Google Scholar is important because it calls attention to BP assessment in HD patients and looks beyond conventional peridialytic BP to analyzing patterns of peridialytic BP. Whereas interdialytic ambulatory BP measurement is the gold standard for the diagnosis of hypertension in HD patients, its implementation can be difficult, and it is not readily available in most HD units. Routine use of peridialytic BP measurement represents the other end of the spectrum because these BP recordings are obtained easily, but have less reproducibility and utility. The median value from intradialytic BP measurements and peridialytic BP recordings may represent an acceptable compromise between utility and practicality. With respect to intradialytic BP measurements, additional studies are required on multiple fronts. First, larger studies are needed to confirm the diagnostic performance of intradialytic BP recordings. Second, it is unknown whether intradialytic BP correlates with end-organ damage or hard outcomes, such as cardiovascular events and mortality. Third, because this study focuses on the pattern of peridialytic BP and patterns of interdialytic ambulatory BP appear to be associated with volume status and arterial stiffness,35Agarwal R. Light R.P. Arterial stiffness and interdialytic weight gain influence ambulatory blood pressure patterns in hemodialysis patients.Am J Physiol Renal Physiol. 2007; 294: F303-F308Crossref PubMed Scopus (57) Google Scholar the pattern of intradialytic BP warrants further investigation. There still is no consensus on the best overall measure of BP in HD patients from the point of view of patients, practitioners, or the health care system. However, based on current evidence, we must look beyond routine peridialytic BP. Intradialytic BP is a candidate for a compromise between scientific rigor and everyday ease of use. However, a paradigm shift appears to be indicated when managing hypertension among hemodialysis patients36Pickering T.G. Miller N.H. Ogedegbe G. et al.Call to action on use and reimbursement for home blood pressure monitoring: a joint scientific statement from the American Heart Association, American Society of Hypertension, and Preventive Cardiovascular Nurses Association.Hypertension. 2008; 52: 10-29Crossref PubMed Scopus (396) Google Scholar; BP values obtained during dialysis should be used to ensure hemodynamic stability, and home BP measurement should be used to diagnose and treat hypertension.3Agarwal R. Sinha A.D. Cardiovascular protection with antihypertensive drugs in dialysis patients: systematic review and meta-analysis.Hypertension. 2009; 53: 860-866Crossref PubMed Scopus (156) Google Scholar, 37Agarwal R. How should hypertension be assessed and managed in hemodialysis patients? Home BP, not dialysis unit BP, should be used for managing hypertension.Semin Dial. 2007; 20: 402-405Crossref PubMed Scopus (13) Google Scholar Financial Disclosure: None. 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 StudyAmerican Journal of Kidney DiseasesVol. 54Issue 5PreviewIntradialytic 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. Full-Text PDF