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Home Blood Pressure Monitoring in CKD
In Practice Home Blood Pressure Monitoring in CKD Debbie L. Cohen, MD, Yonghong Huan, MD, and Raymond R. Townsend, MD Hypertension is common in patients with chronic kidney disease (CKD) and the prevalence increases with declining kidney function. Hypertension management is particularly important due to the increased risk of cardiovascular disease and stroke in the CKD population. Most clinical decisions for blood pressure (BP) management are based on BP readings in the office or dialysis unit. These BP readings often are inaccurate. Home BP monitoring provides more data than conventional clinic or dialysis-unit BP measurements and is relatively easy to accomplish, is cost-effective, and has been shown to have an increasing role in the management of BP in the CKD population. This In Practice article focuses on the use of home BP monitoring in patients with CKD. We also provide guidance for choosing a BP monitoring device and review recent literature regarding the use of home BP monitoring and the effect on CKD outcomes. In addition, we address the future use of electronic medical records and how they may interface with home BP monitoring. Am J Kidney Dis. 63(5):835-842. ª 2014 by the National Kidney Foundation, Inc. INDEX WORDS: Hypertension; home blood pressure (BP) monitoring; office blood pressure (BP) monitoring; chronic kidney disease (CKD); electronic medical records; dialysis.
CASE PRESENTATION Case 1 An 83-year-old African American man with long-standing hypertension and chronic kidney disease (CKD) stage 3 due to hypertensive nephrosclerosis has a baseline creatinine level of 1.51.7 mg/dL for the past 3 years, with an estimated glomerular filtration rate (eGFR) of 45-50 mL/min/1.73 m2 using the CKDEPI (CKD Epidemiology Collaboration) equation.1 He was referred to the hypertension clinic for evaluation of uncontrolled hypertension despite being on treatment with multiple antihypertensive medications, including hydrochlorothiazide, 25 mg, daily; carvedilol, 25 mg, twice daily; nifedipine sustained release, 60 mg, daily; and minoxidil, 2.5 mg, twice daily. Although he reported no symptoms related to his blood pressure (BP) at his initial office visit, he had BP readings of 206/62 mm Hg in the right arm and 206/60 mm Hg in the left arm and a pulse rate of 66 beats/min. Amiloride, 5 mg, daily was added for better BP control because his persistently low renin activity level , 0.1 ng/mL/h suggested saltsensitive hypertension. He was instructed to check his home BP twice daily, in the morning after getting up and in the evening before going to bed, using an automated BP monitor with a properly fitted upper-arm cuff. During subsequent visits, his office BP readings were somewhat lower, but remained elevated in the range of 160-180/70 mm Hg, while his home BP readings were mostly normal in the range of 120-140/60 mm Hg.
Case 2 A 72-year-old white woman with long-standing hypertension, peripheral vascular disease, and CKD stage 4 with a baseline creatinine level of 3.0 mg/dL (eGFR, 15 mL/min/1.73 m2 using the CKD-EPI equation) was referred to the hypertension clinic for evaluation of labile blood pressure. During her initial office visit, she brought in a long list of antihypertensive medications, including clonidine, nifedipine, carvedilol, doxazosin, and furosemide, and a notebook of home BP recordings with BP readings ranging from 100-200/50-80 mm Hg with many self-guided adjustments of antihypertensive medications per her home BP readings. It appeared that she would check BP frequently, sometimes every 1-2 hours, and take several extra doses of clonidine and/or carvedilol in a few hours for elevated BP readings and then hold BP medications for low BP readings. She appeared anxious and tearful during her initial office visit and expressed frustration over her labile BP. Because the Am J Kidney Dis. 2014;63(5):835-842
frequent self-guided adjustment of her BP medications, especially clonidine and carvedilol, was suspected to play a role in her labile BP, she was instructed to check BP less frequently and limit it to twice daily (in the morning after getting up and in the evening before going to bed) and avoid the frequent self-guided adjustment of antihypertensive medications.
Case 3 A 65-year-old African American woman with hypertension and CKD stage 3 due to prior nonsteroidal anti-inflammatory drug use has a baseline creatinine level of 1.5 mg/dL (eGFR, 42 mL/min/ 1.73 m2 using the CKD-EPI equation). She was on metoprolol, losartan, and hydrochlorothiazide therapy for BP control. She was instructed to check home BP twice daily, in the morning after getting up and in the evening before going to bed, using an automated device with a properly fitted upper-arm cuff. Although her office BP readings mostly were in the range of 130-136/60-66 mm Hg, her home BP readings remained in the range of 140-150/60-66 mm Hg. She was instructed to bring in her home BP device to her next office visit, and no further medication adjustments were made.
INTRODUCTION Hypertension is a major public health issue and affects approximately 74 million adults in the United States. Hypertension is common in patients with CKD, and the prevalence of hypertension increases as From the Renal, Electrolyte and Hypertension Division, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA. Received September 3, 2013. Accepted in revised form December 11, 2013. Originally published online February 14, 2014. Address correspondence to Debbie Cohen, MD, Perelman School of Medicine at the University of Pennsylvania, Renal, Electrolyte and Hypertension Division, 1 Founders Bldg, 3400 Spruce St, Philadelphia, PA 19104. E-mail: debbie.cohen@uphs. upenn.edu 2014 by the National Kidney Foundation, Inc. 0272-6386/$36.00 http://dx.doi.org/10.1053/j.ajkd.2013.12.015 835
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overall kidney function deteriorates, ranging from 60%-100%, depending on the population studied.2 The MDRD (Modification of Diet in Renal Disease) Study, which included a large cohort of patients with varying degrees of decreased kidney function, showed an 83% prevalence of hypertension in patients with CKD.3 The prevalence of hypertension increased from 65% in patients with normal or nearnormal kidney function (with GFR of w83 mL/min/ 1.73 m2) to .95% when GFR was w12 mL/min/ 1.73 m2.3 More recently, the Chronic Renal Insufficiency Cohort (CRIC) study also observed an 86% prevalence of hypertension, which ranged from 67% in those with eGFR . 59 mL/min/1.73 m2 to 92% in those with eGFR , 30 mL/min/1.73 m2.4 Management of hypertension in this population is particularly important because coexistent hypertension in patients with CKD and end-stage renal disease (ESRD) increases cardiovascular morbidity and mortality and stroke risk. Most clinical management of hypertension is based on office BP readings in patients with CKD and pre- and postdialysis BP readings obtained in the dialysis clinic in patients with ESRD. Ambulatory BP measurement is the gold standard for BP measurement and is linked most closely with cardiovascular and stroke outcomes,5,6 but this often is impractical because of poor reimbursement or lack of access. Home BP monitoring is an increasingly acceptable alternative to both office and ambulatory BP monitoring because it provides more data than conventional office or dialysis-unit BP measurements and is relatively easy to accomplish. However, home BP monitoring cannot provide data about night-time dipping and early-morning BP surges, which can only be assessed accurately using ambulatory BP monitoring. Night-time dipping in particular has been shown to provide a more accurate prediction of renal and cardiovascular risk in patients with CKD.6 This In Practice article details the various methods of BP measurement and focuses on the utility and efficacy of home BP monitoring in patients with CKD. We provide guidance for choosing a BP monitoring device and review recent literature regarding the use of home BP monitoring and the effect on CKD outcomes. We also address the future use of electronic medical records and how they may interface with home BP monitoring.
TERMINOLOGY AND TECHNOLOGY FOR BP MONITORING The different types of BP monitoring are listed in Box 1. Office BP monitoring is defined as BP measurements obtained by health professionals during office visits or clinical encounters. Home BP monitoring refers to self BP measurements obtained by 836
patients or their caregivers at home or outside clinical settings. Ambulatory BP monitoring obtains BP measurements at regular intervals (every 15-20 minutes during the day and every 30-60 minutes during the night) by an automated BP device during a 24-hour period including a complete cycle of sleep and wakefulness. During the 24-hour period, patients are instructed to make detailed recordings of activities and events. Ambulatory BP monitoring requires the assistance of health care professionals to put on the automated BP device and retrieve BP readings from the automated BP device. Electronic BP monitoring refers to BP measurements obtained by patients or their caregivers at home or outside clinical settings; these readings then are transmitted electronically and incorporated into the electronic medical records for the purpose of managing BP control and medication adjustment. An adequate BP monitor may be manual or automated. It should provide accurate and reliable BP measurements. A monitor with an upper-arm BP cuff is recommended because upper-arm BP is more reliable than wrist or finger BP measurements and is the source of all data supporting the benefit of treating elevated BP. A good BP monitor also requires a cuff properly fitted to the arm size of each patient because a cuff that is too small will give falsely elevated BP measurements. In addition, a good BP monitor should be easy to use and have appropriate accommodating features for patients with disabilities, such as large fonts or voice assistance for patients with visual impairment. Durable and relatively inexpensive BP monitoring devices are widely available. Box 2 summarizes the characteristics of a good home BP monitor. Box 1. Different Types of BP Monitoring
Office BP monitoring: BP measurements obtained by health care professionals during office visits or other clinical encounters; normal BP , 140/90 mm Hg in CKD; ,130/80 mm Hg in proteinuric CKDa Home BP monitoring: BP measurements obtained by patients or their caregivers at home or outside clinical settings; normal BP , 140/90 mm Hg Ambulatory BP monitoring: BP measurements obtained by an automated device at regular intervals (usually every 15-20 min during the day and every 20-30 min during the night) throughout a 24-h period including a complete cycle of wakefulness and sleep; normal BP , 135/85 mm Hg Electronic BP monitoring: BP measurements obtained by patients or their caregiver at home or outside clinical settings that are transmitted electronically to health care providers for the purpose of assessing BP control and managing antihypertensive medications; normal BP , 140/90 mm Hg
Abbreviations: BP, blood pressure; CKD, chronic kidney disease. a The normal BP ranges given are opinion based.
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It is important for practitioners who interpret outof-office BP data to understand some fundamental differences in how most home BP monitors work, as compared to office-based readings using aneroid BP devices and a stethoscope. Most home devices inflate rapidly, sometimes with detection technology that allows the cuff to sense when pulsations are absent so that the cuff then can inflate about 20 mm Hg more and begin deflation. As deflation proceeds, the cuff detects increasing amplitude in the pulse volume, as shown in Fig 1. When the amplitude reaches maximum, representing mean arterial pressure, the cuff then deflates and in most cases estimates systolic (SBP) and diastolic BP from a proprietary algorithm built into the BP device. Most home devices take a BP reading more quickly than an office-based auscultatory method, partly because they have a higher bleed-down rate than the American Heart Association recommendation of 2–mm Hg decrease per heart beat.7 There are 2 reasons to be aware of this. First, patients often do not read the directions that come with monitors, and until practitioners assure themselves that the patient is using good technique, it is difficult to place confidence in the home BP readings because there is no built-in quality control. Second and more importantly, not all monitors will give the same SBP value on a particular patient because the monitors use proprietary internal algorithms. For example, we performed a study of 2 different ambulatory BP monitors worn at the same time. Although they agreed well on mean arterial pressure (which generally is not used clinically to manage BP medications), they were 7 mm Hg different in SBP, even when taking into account whether the dominant or nondominant arm was used.8 Moreover, they frequently are not individually validated, but cite other monitors using similar technology.
HOME BP MONITORING IN EARLIER STAGES OF CKD Current guidelines establish target BP in patients with CKD as an office BP , 130/80 mm Hg in patients with albuminuria (albumin excretion . 30 mg/d) and ,140/90 mm Hg in patients without albuminuria. Office BP monitoring may inaccurately classify patients with CKD, leading to an overdiagnosis of hypertension due to white-coat hypertension and an underdiagnosis of hypertension due to masked Box 2. Characteristics of Good Home BP Monitoring Devices 1. Provide reliable and accurate BP measurements 2. Have properly fitted upper-arm cuff according to the arm size of each patient 3. Easy to use and have appropriate accommodating features for patients with disabilities 4. Durable and relatively inexpensive Abbreviation: BP, blood pressure. Am J Kidney Dis. 2014;63(5):835-842
Figure 1. Graphic shows deflation pressure steps (solid line with down-step pattern, each step is bracketed by 2 closed circles) on y axis and time on x axis. Undulating line shows blood pressure (BP) pulsation amplitude as detected by the cuff. Maximum amplitude is shown at the point marked by the *. This point corresponded to a mean arterial pressure of 128 mm Hg, which is shown by the horizontal line. In this patient, BP was displayed as “151/117 mm Hg.”
hypertension. White-coat hypertension is defined as a patient who has BP . 140/90 mm Hg in the office with reliable out-of-office readings , 140/90 mm Hg. Masked hypertension is defined as elevated home BP readings with normal office BP readings , 140/ 90 mm Hg. Home BP and ambulatory BP monitoring are useful tools to help diagnose both these conditions. Compared with ambulatory BP readings, home BP monitoring in patients with CKD has been shown to be superior to office BP monitoring in diagnosing hypertension and reducing incidences of white-coat hypertension and masked hypertension.9 In a study of 232 veterans with CKD (96% men), Agarwal et al9 compared a single ambulatory BP recording with an average of 2 office BP measurements on 2 occasions and with 1 week of home BP monitoring (an average of 3 readings taken once daily in the morning, afternoon, and evening). Results showed that 1 week of averaged home BP readings . 140/80 mm Hg were associated with an awake ambulatory BP . 130/80 mm Hg, which is considered hypertensive in the CKD population. These SBP and diastolic BP thresholds were found to have both sensitivity and specificity . 80%, making home BP readings a useful measurement to base clinical decisions upon. In addition, w30% of these patients had white-coat hypertension using office BP, but only 24% of patients had white-coat hypertension using home BP monitoring,9 and masked hypertension was present in 26%-29% of patients using office BP measurements, but only 13% when using home BP measurements. Thus, the use of home BP monitoring in patients with CKD appears to be more reliable and also may reduce the incidence of whitecoat or masked hypertension. 837
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HOME BP MONITORING IN DIALYSIS PATIENTS Hypertension is very common in dialysis patients. Based on multiple studies, the prevalence of hypertension has been observed to be more than 50%-60% of patients on hemodialysis therapy and be nearly 30% in patients on peritoneal dialysis therapy.10-12 It should be noted that these prevalence ranges are much lower than the incidence of hypertension at dialysis therapy initiation, which is .80% due largely to better volume control in most patients.13 BP has marked variability in hemodialysis patients due to massive volume shifts, and this makes both the diagnosis and management of hypertension in this population especially challenging. Peritoneal dialysis patients differ from hemodialysis patients in that they do not have large fluid shifts and undergo daily dialysis treatments with more stable fluid balance and BP measurements. Home BP readings, when compared to pre- or postdialysis BP readings, have been shown to correlate more closely with ambulatory BP readings in dialysis patients.14 Studies using ambulatory BP monitoring have used 44-hour readings as opposed to 24 hours to improve accuracy, and this is done in the interdialytic period between hemodialysis treatments. Due to the closer correlation between ambulatory and home BP readings as opposed to between ambulatory and BP readings taken pre- and postdialysis, it can be very useful to use home BP monitoring in both the diagnosis and management of hypertension in dialysis patients.14 Home BP readings also are more reproducible from one week to the next compared with pre- or postdialysis BP readings.15 Home BP can be used to guide the management of BP in dialysis patients and is useful to track changes in BP induced by reducing dry weight.15,16 In patients on hemodialysis therapy, a home BP $ 150/80 mm Hg has been shown to have both sensitivity and specificity . 80% in diagnosing hypertension as defined by data from 44-hour ambulatory BP measurement.17,18 Peritoneal dialysis patients are regarded as hypertensive if office BP is .140/90 mm Hg. A 2009 study randomly assigned 65 stable hemodialysis patients to therapy based on home BP readings versus predialysis BP readings, with a primary end point of assessing change in interdialytic ambulatory BP and change in echocardiographic left ventricular (LV) mass index at 6 months.19 There was no change in ambulatory BP at 6 months in the predialysis BP group; however, a significant decrease in ambulatory BP was noted in the home BP readings group. Between-group BP differences were significant. Given the small number of patients and variability in timing of echocardiographic LV mass measurements, no between-group differences were 838
noted in LV mass index values. The superiority of home BP readings also was demonstrated in another trial that randomly assigned 17 hemodialysis patients to usual care and 17 to home BP monitoring. This study showed a significant improvement in average weekly SBP in the home BP group only.20 The frequency and timing of home BP monitoring also is important in dialysis patients. Home BP increases on average at a rate of 4 mm Hg every 10 hours elapsed after dialysis.21 Measurement of BP soon after or just before dialysis will under- or overestimate BP and therefore it is important to measure BP at various intervals after dialysis.22 It is recommended that BP be measured twice daily, when waking up in the morning and just before going to sleep, for 4 days following a midweek dialysis session.23 These measurements allow an adequate number of readings to diagnose and manage hypertension. For stable dialysis patients, monthly home measurements of interdialytic BP should be encouraged. In a prospective study of 41 long-term hemodialysis patients, 44-hour interdialytic ambulatory BP monitoring was performed before and after stopping their antihypertensive medications.24 Home BP was monitored weekly during the washout period. Eighty percent of patients became hypertensive, but 20% remained normotensive at 3-4 weeks. Patients who remained normotensive had lower home BP readings at baseline and lower LV mass index values. None of the normotensive individuals were volume overloaded as assessed by echocardiography after dialysis versus 12% of hypertensive patients. These results suggest that up to 20% of dialysis patients treated for hypertension may be candidates for drug dosage reductions if home or ambulatory BP measurements were used to assess hypertension rather than predialysis BP recordings. In a study of 32 peritoneal dialysis patients, the relationship between home BP monitoring and 24-hour ambulatory BP monitoring was evaluated. Home BP was taken as the 10-day average of 3 BP readings obtained in the morning. There was a high correlation between home BP and 24-hour ambulatory BP monitoring values (r 5 0.54-0.71) and similar correlations also were obtained between office and ambulatory BP monitoring. The impact of home BP on the diagnosis of hypertension and target-organ damage was not assessed.25 These data suggest that home BP monitoring may add value to the diagnosis of hypertension in peritoneal dialysis patients.
HOME BP MEASUREMENT AND OUTCOMES Compared with ambulatory BP readings, home BP readings provide more accurate readings than office BP readings in patients with earlier stages of CKD Am J Kidney Dis. 2014;63(5):835-842
Home Blood Pressure Monitoring in CKD
and ESRD, but do home BP readings correlate with target-organ damage, increased cardiovascular risk, or progression of CKD? A number of studies have attempted to address this issue in the CKD and dialysis populations, as shown in Table 1. Studies in Earlier Stages of CKD Out-of-office BP readings in patients with CKD are associated strongly with target-organ damage.26 Home BP monitoring has been shown to correlate with proteinuria and decline in eGFR. One study showed that proteinuria was the strongest correlate of SBP by any BP measurement technique, and this was correlated most closely with both home and ambulatory BP measurements.27 In another study of 77 patients with type 1 diabetic nephropathy who were followed up for 6 years, home BP was a stronger predictor of decrease in GFR than office BP.28 A study from Japan assessed the ability of office versus home BP measurements to predict progression of kidney disease in 113 patients with CKD who were followed up for 3 years. Although both office and home BP readings were correlated significantly with decrease in kidney function as assessed by eGFR, home BP measured in the morning had the strongest correlation with yearly decline in eGFR.29 In a study of elderly patients older than 70 years from Japan with CKD stages 3-5, home BP was measured every morning and evening for 7 consecutive days. Home BP readings were obtained every 6 months for 79 of 104 of these patients, and mean duration of follow-up was 39 months. The study results showed significant correlations between morning SBP, evening SBP, and change in GFR during the follow-up period. Stepwise multivariate regression analysis showed that morning SBP and proteinuria were independent predictors of change in GFR. This study showed that home BP monitoring as compared to office BP is a significant predictor of decrease in kidney function and development of ESRD. However, the study did not find a significant association between office or home BP and risk of death or cardiovascular events.30
A prospective cohort study of 217 veterans with CKD was conducted to assess how well home BP readings predict ESRD and death.31 Patients had home BP measured, ambulatory BP monitoring performed, and BP measured in the clinic by routine and standardized methods. Routine BP was measured as usually done in the clinic, and standardized BP was measured according to a protocol by trained personal. Patients were followed up for a median of 3.5 years. Seventy-five patients experienced the primary combined end point of ESRD or death, and 39 of these patients died prior to starting dialysis therapy. All types of measured SBP significantly predicted ESRD, death, or the combined end point, but routine clinic SBP did not predict death. However, home BP readings were most predictive for each end point. The same cohort also was studied to define the relationship between BP measurement type and combined end point of myocardial infarction, stroke, and all-cause mortality. Average home BP was 147/78 mm Hg, 24-hour ambulatory BP was 134/73 mm Hg, and office BP was 155/85 mm Hg by the standardized method and 145/75 mm Hg by the routine method. A 1-SD increase in SBP increased the hazard ratio of the composite end point by 1.16 for routine BP, 1.57 for standardized BP, 1.66 for home BP, and 1.42 for 24-hour ambulatory BP readings. In comparison to BP measured in the office, home BP was associated more strongly with the composite outcome.32 These studies support the prognostic value of using home BP in patients with CKD to predict target-organ damage, decrease in kidney function, cardiovascular events, and death. Studies in Dialysis In patients on hemodialysis therapy, a U-shaped curve has been observed for the association between SBP and mortality. Patients with the lowest SBP have the highest mortality, and there is a small increase in mortality in patients with very high pre- or postdialysis BP readings.33 Interdialytic BP readings done in dialysis patients outside the dialysis unit have been shown to
Table 1. Studies of Home BP Monitoring in Patients With CKD Study
Country
CKD or HD
Germany
CKD/DN
77
6.2
Decline in eGFR
Japan
CKD
113
3.0
Decline in eGFR
Agarwal & Andersen27
USA
CKD
217
3.5
ESRD, death
Agarwal & Andersen32
USA
CKD
217
3.4
CV events, death
Okada et al30
Japan
CKD
79
3.2
Decline in eGFR and ESRD; no increase in CV events
Alborzi et al18
USA
HD
150
2.0
CV mortality, death
Agarwal42
USA
HD
326
2.4
Death
Rave et al28 Suzuki et al29
N
Follow-up (y)
Outcomes
Abbreviations: BP, blood pressure; CKD, chronic kidney disease; CV, cardiovascular; DN, diabetic nephropathy; eGFR, estimated glomerular filtration rate; ESRD, end-stage renal disease; HD, hemodialysis. Am J Kidney Dis. 2014;63(5):835-842
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predict target-organ damage, including LV hypertrophy and mortality.18,34-38 In an observational study, 101 dialysis patients used daily home BP monitoring to record a total of 20 BP readings over a 1-week period, including measurements of wake-up and night BP readings. BP also was recorded pre- and postdialysis 3 times per week. The relationship between the weekly averaged BP readings and LV hypertrophy and aortic stiffness (reflecting vascular target-organ damage) were assessed.39 The weekly averaged BP readings showed a significant correlation with LV mass index and pulse wave velocity as a marker of aortic stiffness, whereas predialysis BP did not show a positive correlation.35 Another study by the same group in 96 dialysis patients showed that pulse pressures derived from within and outside the dialysis clinic, when averaged over a 1-week period, were predictive of cardiovascular mortality and all-cause mortality.36 In a survey of 150 long-term hemodialysis patients, home BP monitoring had a superior ability to indicate the presence of LV hypertrophy compared with predialysis readings.34 In a longitudinal follow-up to this study, patients with elevated home BP readings also were found to have higher mortality, whereas dialysis clinic readings did not correlate with this outcome. In summary, home BP monitoring is correlated better than office BP with target-organ damage in dialysis patients and has greater value in predicting cardiovascular and all-cause mortality.
THE FUTURE: INTERFACE WITH ELECTRONIC MEDICAL RECORDS As shown in Fig 2, there are several ways in which patient-level BP data can be added to the patient’s health record. The current technologies allow both
blue tooth and direct internet connections to transmit electronic BP data directly to a personalized health record portal. Large electronic medical record systems in the United States have not adapted to this emerging technology; however, it is our hope that market forces will press them into greater responsiveness. The value of direct data entry is that not only can the data be displayed graphically and subjected to a variety of statistical trends, such as average BP or a measure of variability in BP, they also can be aggregated at a provider level for quality metrics that allow a health care professional to see what level of out-of-office BP control is present in his or her population of patients undertaking such measures. Manually entered BP recordings also are of benefit, but electronic BP recordings have the advantage in that they reduce the requirement for staff to enter the data and reduce the potential for transcription errors. As health care systems continue to grow, BP data for a health system can be aggregated and used to train and educate providers and identify outlier patients who could benefit from specific high-BP referrals. Success stories for such use of large volumes of BP data used to manage a health system include the Kaiser Permanente and Veterans Administration Medical Center experiences.40,41
CONCLUSIONS Many patients measure BP outside the office. It is our opinion that home BP monitoring will have an increasingly important role in the management of BP in patients with CKD in the future. We acknowledge that patients with white-coat hypertension have been included in many prior clinical hypertension studies, whereas patients with masked hypertension probably have been excluded from many clinical studies.
Figure 2. Graphic depicts methods for placing out-of-office blood pressure (BP) data into patient records. (Upper panel) The patient is properly positioned, with arm/back/feet supported. The data are kept by the patient, brought to the visit, and then either scanned, copied, or attached to the paper or electronic chart (no portal for direct entry). (Lower panel) The same patient measures BP with a BP device (BPD) that can access directly to the electronic health record (EHR) by an internet portal. The sine wave line shows data uplink. Once part of the EHR, the BP data can be viewed at each visit, tallied, averaged, variability computed, and/or added to a secure database for quality metrics. 840
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Therefore, we base most of our opinions on studies in which BP has been measured in the office setting. We believe that our role as health care providers should be to encourage home BP monitoring, and this should include oversight of the patient’s technique to ensure that the data are trustworthy, encouraging the use of monitors that have been subjected to validation procedures (see www.dableducational.org for an example of a website that discusses home BP monitor validation), and working with electronic medical record companies to develop and improve patient portals and BP data management and display functions. Exciting developments in the area of BP monitoring include home BP monitors that incorporate blood glucose measurement capability, and also cuffless methodologies that are promising for greater BP data acquisition (including nocturnal values) without the disturbance of cuff inflations (see, eg, the Contipress at www.senseas.com/contipress). One note of caution needs to be stated in closing. Although we are enthusiastic about the ability to gain more information about a patient’s BP pattern by using home BP measurements, there still is a need to show that such knowledge can be translated into true cardiovascular benefit because most prior outcome studies have used office BP readings when assessing BP measurements. At present, the benefits of home monitoring are greater patient empowerment in their care, insight into the connection of BP (and heart rate) with symptoms, and in some cases, better control with less medicine and/or greater attention to lifestyle measures by the patient. In embracing the growing popularity of home BP monitoring, it is important to determine that we truly are benefitting the target organs in the process. We still await the data showing this.
CASE REVIEW Case 1 To ensure the accuracy of the patient’s home BP monitor, he brought in his automated BP device during one of his office visits. While in the office, his home BP monitor and the office BP device showed similarly elevated BP readings of 180-188/60-68 mm Hg. Home BP monitoring was helpful and supported the diagnosis of white-coat hypertension. Further medication adjustments were not needed. Case 2 During subsequent office visits, the patient’s home BP recordings showed less labile BP readings, but more persistent elevation of BP in the range of 150-160/60-70 mm Hg, comparable to her BP readings obtained during the office visits. The furosemide dosage was increased from daily to twice daily and spironolactone was added, and it resulted in reductions Am J Kidney Dis. 2014;63(5):835-842
in both home and office BP to the range of 130-140/6070 mm Hg. Case 3 To ensure accurate home BP readings, the patient brought in her home BP device during an office visit, and the home BP monitor had BP readings similar to the office BP device, supporting the diagnosis of masked uncontrolled hypertension. Amlodipine was added, with further reduction of home BP to the range of 120-130/60-66 mm Hg.
ACKNOWLEDGEMENTS Support: None. Financial Disclosure: The authors declare that they have no relevant financial interests.
REFERENCES 1. Levey AS, Stevens LA, Schmid CH, et al. A new equation to estimate glomerular filtration rate. Ann Intern Med. 2009;150(9): 604-612. 2. Mailloux LU, Levey AS. Hypertension in patients with chronic renal disease. Am J Kidney Dis. 1998;32(5)(suppl 3):S120-S141. 3. Buckalew VM Jr, Berg RL, Wang SR, Porush JG, Rauch S, Schulman G. Prevalence of hypertension in 1,795 subjects with chronic renal disease: the Modification of Diet in Renal Disease Study baseline cohort. Modification of Diet in Renal Disease Study Group. Am J Kidney Dis. 1996;28(6):811-821. 4. Muntner P, Anderson A, Charleston J, et al. Hypertension awareness, treatment, and control in adults with CKD: results from the Chronic Renal Insufficiency Cohort (CRIC) Study. Am J Kidney Dis. 2010;55(3):441-451. 5. Hermida RC, Smolensky MH, Ayala DE, Portaluppi F. 2013 Ambulatory blood pressure monitoring recommendations for the diagnosis of adult hypertension, assessment of cardiovascular and other hypertension-associated risk, and attainment of therapeutic goals. Chronobiol Int. 2013;30(3):355-410. 6. Minutolo R, Agarwal R, Borrelli S, et al. Prognostic role of ambulatory blood pressure measurement in patients with nondialysis chronic kidney disease. Arch Intern Med. 2011;171(12):1090-1098. 7. Pickering TG, Miller NH, Ogedegbe G, Krakoff LR, Artinian NT, Goff D. 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(1):10-29. 8. Kallem RR, Meyers KE, Sawinski DL, Townsend RR. A comparison of two ambulatory blood pressure monitors worn at the same time. J Clin Hypertens (Greenwich). 2013;15(5):321-325. 9. Andersen MJ, Khawandi W, Agarwal R. Home blood pressure monitoring in CKD. Am J Kidney Dis. 2005;45(6):994-1001. 10. Rahman M, Dixit A, Donley V, et al. Factors associated with inadequate blood pressure control in hypertensive hemodialysis patients. Am J Kidney Dis. 1999;33(3):498-506. 11. Agarwal R, Nissenson AR, Batlle D, Coyne DW, Trout JR, Warnock DG. Prevalence, treatment, and control of hypertension in chronic hemodialysis patients in the United States. Am J Med. 2003;115(4):291-297. 12. Rocco MV, Flanigan MJ, Beaver S, et al. Report from the 1995 Core Indicators for Peritoneal Dialysis Study Group. Am J Kidney Dis. 1997;30(2):165-173. 841
Cohen, Huan, and Townsend 13. Zucchelli P, Santoro A, Zuccala A. Genesis and control of hypertension in hemodialysis patients. Semin Nephrol. 1988;8(2):163-168. 14. Agarwal R. Managing hypertension using home blood pressure monitoring among haemodialysis patients—a call to action. Nephrol Dial Transplant. 2010;25(6):1766-1771. 15. Agarwal R, Satyan S, Alborzi P, et al. Home blood pressure measurements for managing hypertension in hemodialysis patients. Am J Nephrol. 2009;30(2):126-134. 16. Deziel C, Bouchard J, Zellweger M, Madore F. Impact of hemocontrol on hypertension, nursing interventions, and quality of life: a randomized, controlled trial. Clin J Am Soc Nephrol. 2007;2(4):661-668. 17. Agarwal R, Peixoto AJ, Santos SF, Zoccali C. Out-of-office blood pressure monitoring in chronic kidney disease. Blood Press Monit. 2009;14(1):2-11. 18. Alborzi P, Patel N, Agarwal R. Home blood pressures are of greater prognostic value than hemodialysis unit recordings. Clin J Am Soc Nephrol. 2007;2(6):1228-1234. 19. da Silva GV, de Barros S, Abensur H, Ortega KC, Mion D Jr. Home blood pressure monitoring in blood pressure control among haemodialysis patients: an open randomized clinical trial. Nephrol Dial Transplant. 2009;24(12):3805-3811. 20. Kauric-Klein Z, Artinian N. Improving blood pressure control in hypertensive hemodialysis patients. CANNT J. 2007;17(4):24-28, 31-36; quiz 29-30, 37-38. 21. Agarwal R, Light RP. Chronobiology of arterial hypertension in hemodialysis patients: implications for home blood pressure monitoring. Am J Kidney Dis. 2009;54(4):693-701. 22. Mitra S, Chandna SM, Farrington K. What is hypertension in chronic haemodialysis? The role of interdialytic blood pressure monitoring. Nephrol Dial Transplant. 1999;14(12):2915-2921. 23. Agarwal R, Andersen MJ, Light RP. Location not quantity of blood pressure measurements predicts mortality in hemodialysis patients. Am J Nephrol. 2008;28(2):210-217. 24. Bishu K, Gricz KM, Chewaka S, Agarwal R. Appropriateness of antihypertensive drug therapy in hemodialysis patients. Clin J Am Soc Nephrol. 2006;1(4):820-824. 25. Wang MC, Tseng CC, Tsai WC, Huang JJ. Blood pressure and left ventricular hypertrophy in patients on different peritoneal dialysis regimens. Perit Dial Int. 2001;21(1):36-42. 26. Agarwal R. Home and ambulatory blood pressure monitoring in chronic kidney disease. Curr Opin Nephrol Hypertens. 2009;18(6):507-512. 27. Agarwal R, Andersen MJ. Prognostic importance of ambulatory blood pressure recordings in patients with chronic kidney disease. Kidney Int. 2006;69(7):1175-1180. 28. Rave K, Bender R, Heise T, Sawicki PT. Value of blood pressure self-monitoring as a predictor of progression of diabetic nephropathy. J Hypertens. 1999;17(5):597-601.
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29. Suzuki H, Nakamoto H, Okada H, Sugahara S, Kanno Y. Self-measured systolic blood pressure in the morning is a strong indicator of decline of renal function in hypertensive patients with non-diabetic chronic renal insufficiency. Clin Exp Hypertens. 2002;24(4):249-260. 30. Okada T, Nakao T, Matsumoto H, et al. Prognostic significance of home blood pressure control on renal and cardiovascular outcomes in elderly patients with chronic kidney disease. Hypertens Res. 2009;32(12):1123-1129. 31. Agarwal R, Andersen MJ. Prognostic importance of clinic and home blood pressure recordings in patients with chronic kidney disease. Kidney Int. 2006;69(2):406-411. 32. Agarwal R, Andersen MJ. Blood pressure recordings within and outside the clinic and cardiovascular events in chronic kidney disease. Am J Nephrol. 2006;26(5):503-510. 33. Agarwal R. Hypertension and survival in chronic hemodialysis patients—past lessons and future opportunities. Kidney Int. 2005;67(1):1-13. 34. Agarwal R, Brim NJ, Mahenthiran J, Andersen MJ, Saha C. Out-of-hemodialysis-unit blood pressure is a superior determinant of left ventricular hypertrophy. Hypertension. 2006;47(1): 62-68. 35. Moriya H, Ohtake T, Kobayashi S. Aortic stiffness, left ventricular hypertrophy and weekly averaged blood pressure (WAB) in patients on haemodialysis. Nephrol Dial Transplant. 2007;22(4):1198-1204. 36. Moriya H, Oka M, Maesato K, et al. Weekly averaged blood pressure is more important than a single-point blood pressure measurement in the risk stratification of dialysis patients. Clin J Am Soc Nephrol. 2008;3(2):416-422. 37. Amar J, Vernier I, Rossignol E, et al. Nocturnal blood pressure and 24-hour pulse pressure are potent indicators of mortality in hemodialysis patients. Kidney Int. 2000;57(6): 2485-2491. 38. Agarwal R. Hypervolemia is associated with increased mortality among hemodialysis patients. Hypertension. 2010;56(3): 512-517. 39. DeLoach SS, Townsend RR. Vascular stiffness: its measurement and significance for epidemiologic and outcome studies. Clin J Am Soc Nephrol. 2008;3(1):184-192. 40. Fletcher RD, Amdur RL, Kolodner R, et al. Blood pressure control among US veterans: a large multiyear analysis of blood pressure data from the Veterans Administration health data repository. Circulation. 2012;125(20):2462-2468. 41. Jaffe MG, Lee GA, Young JD, Sidney S, Go AS. Improved blood pressure control associated with a large-scale hypertension program. JAMA. 2013;310(7):699-705. 42. Agarwal R. Blood pressure and mortality among hemodialysis patients. Hypertension. 2010;55(3):762-768.
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CASE PRESENTATION Case 1 An 83-year-old African American man with long-standing hypertension and chronic kidney disease (CKD) stage 3 due to hypertensive nephrosclerosis has a baseline creatinine level of 1.51.7 mg/dL for the past 3 years, with an estimated glomerular filtration rate (eGFR) of 45-50 mL/min/1.73 m2 using the CKDEPI (CKD Epidemiology Collaboration) equation.1 He was referred to the hypertension clinic for evaluation of uncontrolled hypertension despite being on treatment with multiple antihypertensive medications, including hydrochlorothiazide, 25 mg, daily; carvedilol, 25 mg, twice daily; nifedipine sustained release, 60 mg, daily; and minoxidil, 2.5 mg, twice daily. Although he reported no symptoms related to his blood pressure (BP) at his initial office visit, he had BP readings of 206/62 mm Hg in the right arm and 206/60 mm Hg in the left arm and a pulse rate of 66 beats/min. Amiloride, 5 mg, daily was added for better BP control because his persistently low renin activity level , 0.1 ng/mL/h suggested saltsensitive hypertension. He was instructed to check his home BP twice daily, in the morning after getting up and in the evening before going to bed, using an automated BP monitor with a properly fitted upper-arm cuff. During subsequent visits, his office BP readings were somewhat lower, but remained elevated in the range of 160-180/70 mm Hg, while his home BP readings were mostly normal in the range of 120-140/60 mm Hg.
Case 2 A 72-year-old white woman with long-standing hypertension, peripheral vascular disease, and CKD stage 4 with a baseline creatinine level of 3.0 mg/dL (eGFR, 15 mL/min/1.73 m2 using the CKD-EPI equation) was referred to the hypertension clinic for evaluation of labile blood pressure. During her initial office visit, she brought in a long list of antihypertensive medications, including clonidine, nifedipine, carvedilol, doxazosin, and furosemide, and a notebook of home BP recordings with BP readings ranging from 100-200/50-80 mm Hg with many self-guided adjustments of antihypertensive medications per her home BP readings. It appeared that she would check BP frequently, sometimes every 1-2 hours, and take several extra doses of clonidine and/or carvedilol in a few hours for elevated BP readings and then hold BP medications for low BP readings. She appeared anxious and tearful during her initial office visit and expressed frustration over her labile BP. Because the Am J Kidney Dis. 2014;63(5):835-842
frequent self-guided adjustment of her BP medications, especially clonidine and carvedilol, was suspected to play a role in her labile BP, she was instructed to check BP less frequently and limit it to twice daily (in the morning after getting up and in the evening before going to bed) and avoid the frequent self-guided adjustment of antihypertensive medications.
Case 3 A 65-year-old African American woman with hypertension and CKD stage 3 due to prior nonsteroidal anti-inflammatory drug use has a baseline creatinine level of 1.5 mg/dL (eGFR, 42 mL/min/ 1.73 m2 using the CKD-EPI equation). She was on metoprolol, losartan, and hydrochlorothiazide therapy for BP control. She was instructed to check home BP twice daily, in the morning after getting up and in the evening before going to bed, using an automated device with a properly fitted upper-arm cuff. Although her office BP readings mostly were in the range of 130-136/60-66 mm Hg, her home BP readings remained in the range of 140-150/60-66 mm Hg. She was instructed to bring in her home BP device to her next office visit, and no further medication adjustments were made.
INTRODUCTION Hypertension is a major public health issue and affects approximately 74 million adults in the United States. Hypertension is common in patients with CKD, and the prevalence of hypertension increases as From the Renal, Electrolyte and Hypertension Division, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA. Received September 3, 2013. Accepted in revised form December 11, 2013. Originally published online February 14, 2014. Address correspondence to Debbie Cohen, MD, Perelman School of Medicine at the University of Pennsylvania, Renal, Electrolyte and Hypertension Division, 1 Founders Bldg, 3400 Spruce St, Philadelphia, PA 19104. E-mail: debbie.cohen@uphs. upenn.edu 2014 by the National Kidney Foundation, Inc. 0272-6386/$36.00 http://dx.doi.org/10.1053/j.ajkd.2013.12.015 835
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overall kidney function deteriorates, ranging from 60%-100%, depending on the population studied.2 The MDRD (Modification of Diet in Renal Disease) Study, which included a large cohort of patients with varying degrees of decreased kidney function, showed an 83% prevalence of hypertension in patients with CKD.3 The prevalence of hypertension increased from 65% in patients with normal or nearnormal kidney function (with GFR of w83 mL/min/ 1.73 m2) to .95% when GFR was w12 mL/min/ 1.73 m2.3 More recently, the Chronic Renal Insufficiency Cohort (CRIC) study also observed an 86% prevalence of hypertension, which ranged from 67% in those with eGFR . 59 mL/min/1.73 m2 to 92% in those with eGFR , 30 mL/min/1.73 m2.4 Management of hypertension in this population is particularly important because coexistent hypertension in patients with CKD and end-stage renal disease (ESRD) increases cardiovascular morbidity and mortality and stroke risk. Most clinical management of hypertension is based on office BP readings in patients with CKD and pre- and postdialysis BP readings obtained in the dialysis clinic in patients with ESRD. Ambulatory BP measurement is the gold standard for BP measurement and is linked most closely with cardiovascular and stroke outcomes,5,6 but this often is impractical because of poor reimbursement or lack of access. Home BP monitoring is an increasingly acceptable alternative to both office and ambulatory BP monitoring because it provides more data than conventional office or dialysis-unit BP measurements and is relatively easy to accomplish. However, home BP monitoring cannot provide data about night-time dipping and early-morning BP surges, which can only be assessed accurately using ambulatory BP monitoring. Night-time dipping in particular has been shown to provide a more accurate prediction of renal and cardiovascular risk in patients with CKD.6 This In Practice article details the various methods of BP measurement and focuses on the utility and efficacy of home BP monitoring in patients with CKD. We provide guidance for choosing a BP monitoring device and review recent literature regarding the use of home BP monitoring and the effect on CKD outcomes. We also address the future use of electronic medical records and how they may interface with home BP monitoring.
TERMINOLOGY AND TECHNOLOGY FOR BP MONITORING The different types of BP monitoring are listed in Box 1. Office BP monitoring is defined as BP measurements obtained by health professionals during office visits or clinical encounters. Home BP monitoring refers to self BP measurements obtained by 836
patients or their caregivers at home or outside clinical settings. Ambulatory BP monitoring obtains BP measurements at regular intervals (every 15-20 minutes during the day and every 30-60 minutes during the night) by an automated BP device during a 24-hour period including a complete cycle of sleep and wakefulness. During the 24-hour period, patients are instructed to make detailed recordings of activities and events. Ambulatory BP monitoring requires the assistance of health care professionals to put on the automated BP device and retrieve BP readings from the automated BP device. Electronic BP monitoring refers to BP measurements obtained by patients or their caregivers at home or outside clinical settings; these readings then are transmitted electronically and incorporated into the electronic medical records for the purpose of managing BP control and medication adjustment. An adequate BP monitor may be manual or automated. It should provide accurate and reliable BP measurements. A monitor with an upper-arm BP cuff is recommended because upper-arm BP is more reliable than wrist or finger BP measurements and is the source of all data supporting the benefit of treating elevated BP. A good BP monitor also requires a cuff properly fitted to the arm size of each patient because a cuff that is too small will give falsely elevated BP measurements. In addition, a good BP monitor should be easy to use and have appropriate accommodating features for patients with disabilities, such as large fonts or voice assistance for patients with visual impairment. Durable and relatively inexpensive BP monitoring devices are widely available. Box 2 summarizes the characteristics of a good home BP monitor. Box 1. Different Types of BP Monitoring
Office BP monitoring: BP measurements obtained by health care professionals during office visits or other clinical encounters; normal BP , 140/90 mm Hg in CKD; ,130/80 mm Hg in proteinuric CKDa Home BP monitoring: BP measurements obtained by patients or their caregivers at home or outside clinical settings; normal BP , 140/90 mm Hg Ambulatory BP monitoring: BP measurements obtained by an automated device at regular intervals (usually every 15-20 min during the day and every 20-30 min during the night) throughout a 24-h period including a complete cycle of wakefulness and sleep; normal BP , 135/85 mm Hg Electronic BP monitoring: BP measurements obtained by patients or their caregiver at home or outside clinical settings that are transmitted electronically to health care providers for the purpose of assessing BP control and managing antihypertensive medications; normal BP , 140/90 mm Hg
Abbreviations: BP, blood pressure; CKD, chronic kidney disease. a The normal BP ranges given are opinion based.
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Home Blood Pressure Monitoring in CKD
It is important for practitioners who interpret outof-office BP data to understand some fundamental differences in how most home BP monitors work, as compared to office-based readings using aneroid BP devices and a stethoscope. Most home devices inflate rapidly, sometimes with detection technology that allows the cuff to sense when pulsations are absent so that the cuff then can inflate about 20 mm Hg more and begin deflation. As deflation proceeds, the cuff detects increasing amplitude in the pulse volume, as shown in Fig 1. When the amplitude reaches maximum, representing mean arterial pressure, the cuff then deflates and in most cases estimates systolic (SBP) and diastolic BP from a proprietary algorithm built into the BP device. Most home devices take a BP reading more quickly than an office-based auscultatory method, partly because they have a higher bleed-down rate than the American Heart Association recommendation of 2–mm Hg decrease per heart beat.7 There are 2 reasons to be aware of this. First, patients often do not read the directions that come with monitors, and until practitioners assure themselves that the patient is using good technique, it is difficult to place confidence in the home BP readings because there is no built-in quality control. Second and more importantly, not all monitors will give the same SBP value on a particular patient because the monitors use proprietary internal algorithms. For example, we performed a study of 2 different ambulatory BP monitors worn at the same time. Although they agreed well on mean arterial pressure (which generally is not used clinically to manage BP medications), they were 7 mm Hg different in SBP, even when taking into account whether the dominant or nondominant arm was used.8 Moreover, they frequently are not individually validated, but cite other monitors using similar technology.
HOME BP MONITORING IN EARLIER STAGES OF CKD Current guidelines establish target BP in patients with CKD as an office BP , 130/80 mm Hg in patients with albuminuria (albumin excretion . 30 mg/d) and ,140/90 mm Hg in patients without albuminuria. Office BP monitoring may inaccurately classify patients with CKD, leading to an overdiagnosis of hypertension due to white-coat hypertension and an underdiagnosis of hypertension due to masked Box 2. Characteristics of Good Home BP Monitoring Devices 1. Provide reliable and accurate BP measurements 2. Have properly fitted upper-arm cuff according to the arm size of each patient 3. Easy to use and have appropriate accommodating features for patients with disabilities 4. Durable and relatively inexpensive Abbreviation: BP, blood pressure. Am J Kidney Dis. 2014;63(5):835-842
Figure 1. Graphic shows deflation pressure steps (solid line with down-step pattern, each step is bracketed by 2 closed circles) on y axis and time on x axis. Undulating line shows blood pressure (BP) pulsation amplitude as detected by the cuff. Maximum amplitude is shown at the point marked by the *. This point corresponded to a mean arterial pressure of 128 mm Hg, which is shown by the horizontal line. In this patient, BP was displayed as “151/117 mm Hg.”
hypertension. White-coat hypertension is defined as a patient who has BP . 140/90 mm Hg in the office with reliable out-of-office readings , 140/90 mm Hg. Masked hypertension is defined as elevated home BP readings with normal office BP readings , 140/ 90 mm Hg. Home BP and ambulatory BP monitoring are useful tools to help diagnose both these conditions. Compared with ambulatory BP readings, home BP monitoring in patients with CKD has been shown to be superior to office BP monitoring in diagnosing hypertension and reducing incidences of white-coat hypertension and masked hypertension.9 In a study of 232 veterans with CKD (96% men), Agarwal et al9 compared a single ambulatory BP recording with an average of 2 office BP measurements on 2 occasions and with 1 week of home BP monitoring (an average of 3 readings taken once daily in the morning, afternoon, and evening). Results showed that 1 week of averaged home BP readings . 140/80 mm Hg were associated with an awake ambulatory BP . 130/80 mm Hg, which is considered hypertensive in the CKD population. These SBP and diastolic BP thresholds were found to have both sensitivity and specificity . 80%, making home BP readings a useful measurement to base clinical decisions upon. In addition, w30% of these patients had white-coat hypertension using office BP, but only 24% of patients had white-coat hypertension using home BP monitoring,9 and masked hypertension was present in 26%-29% of patients using office BP measurements, but only 13% when using home BP measurements. Thus, the use of home BP monitoring in patients with CKD appears to be more reliable and also may reduce the incidence of whitecoat or masked hypertension. 837
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HOME BP MONITORING IN DIALYSIS PATIENTS Hypertension is very common in dialysis patients. Based on multiple studies, the prevalence of hypertension has been observed to be more than 50%-60% of patients on hemodialysis therapy and be nearly 30% in patients on peritoneal dialysis therapy.10-12 It should be noted that these prevalence ranges are much lower than the incidence of hypertension at dialysis therapy initiation, which is .80% due largely to better volume control in most patients.13 BP has marked variability in hemodialysis patients due to massive volume shifts, and this makes both the diagnosis and management of hypertension in this population especially challenging. Peritoneal dialysis patients differ from hemodialysis patients in that they do not have large fluid shifts and undergo daily dialysis treatments with more stable fluid balance and BP measurements. Home BP readings, when compared to pre- or postdialysis BP readings, have been shown to correlate more closely with ambulatory BP readings in dialysis patients.14 Studies using ambulatory BP monitoring have used 44-hour readings as opposed to 24 hours to improve accuracy, and this is done in the interdialytic period between hemodialysis treatments. Due to the closer correlation between ambulatory and home BP readings as opposed to between ambulatory and BP readings taken pre- and postdialysis, it can be very useful to use home BP monitoring in both the diagnosis and management of hypertension in dialysis patients.14 Home BP readings also are more reproducible from one week to the next compared with pre- or postdialysis BP readings.15 Home BP can be used to guide the management of BP in dialysis patients and is useful to track changes in BP induced by reducing dry weight.15,16 In patients on hemodialysis therapy, a home BP $ 150/80 mm Hg has been shown to have both sensitivity and specificity . 80% in diagnosing hypertension as defined by data from 44-hour ambulatory BP measurement.17,18 Peritoneal dialysis patients are regarded as hypertensive if office BP is .140/90 mm Hg. A 2009 study randomly assigned 65 stable hemodialysis patients to therapy based on home BP readings versus predialysis BP readings, with a primary end point of assessing change in interdialytic ambulatory BP and change in echocardiographic left ventricular (LV) mass index at 6 months.19 There was no change in ambulatory BP at 6 months in the predialysis BP group; however, a significant decrease in ambulatory BP was noted in the home BP readings group. Between-group BP differences were significant. Given the small number of patients and variability in timing of echocardiographic LV mass measurements, no between-group differences were 838
noted in LV mass index values. The superiority of home BP readings also was demonstrated in another trial that randomly assigned 17 hemodialysis patients to usual care and 17 to home BP monitoring. This study showed a significant improvement in average weekly SBP in the home BP group only.20 The frequency and timing of home BP monitoring also is important in dialysis patients. Home BP increases on average at a rate of 4 mm Hg every 10 hours elapsed after dialysis.21 Measurement of BP soon after or just before dialysis will under- or overestimate BP and therefore it is important to measure BP at various intervals after dialysis.22 It is recommended that BP be measured twice daily, when waking up in the morning and just before going to sleep, for 4 days following a midweek dialysis session.23 These measurements allow an adequate number of readings to diagnose and manage hypertension. For stable dialysis patients, monthly home measurements of interdialytic BP should be encouraged. In a prospective study of 41 long-term hemodialysis patients, 44-hour interdialytic ambulatory BP monitoring was performed before and after stopping their antihypertensive medications.24 Home BP was monitored weekly during the washout period. Eighty percent of patients became hypertensive, but 20% remained normotensive at 3-4 weeks. Patients who remained normotensive had lower home BP readings at baseline and lower LV mass index values. None of the normotensive individuals were volume overloaded as assessed by echocardiography after dialysis versus 12% of hypertensive patients. These results suggest that up to 20% of dialysis patients treated for hypertension may be candidates for drug dosage reductions if home or ambulatory BP measurements were used to assess hypertension rather than predialysis BP recordings. In a study of 32 peritoneal dialysis patients, the relationship between home BP monitoring and 24-hour ambulatory BP monitoring was evaluated. Home BP was taken as the 10-day average of 3 BP readings obtained in the morning. There was a high correlation between home BP and 24-hour ambulatory BP monitoring values (r 5 0.54-0.71) and similar correlations also were obtained between office and ambulatory BP monitoring. The impact of home BP on the diagnosis of hypertension and target-organ damage was not assessed.25 These data suggest that home BP monitoring may add value to the diagnosis of hypertension in peritoneal dialysis patients.
HOME BP MEASUREMENT AND OUTCOMES Compared with ambulatory BP readings, home BP readings provide more accurate readings than office BP readings in patients with earlier stages of CKD Am J Kidney Dis. 2014;63(5):835-842
Home Blood Pressure Monitoring in CKD
and ESRD, but do home BP readings correlate with target-organ damage, increased cardiovascular risk, or progression of CKD? A number of studies have attempted to address this issue in the CKD and dialysis populations, as shown in Table 1. Studies in Earlier Stages of CKD Out-of-office BP readings in patients with CKD are associated strongly with target-organ damage.26 Home BP monitoring has been shown to correlate with proteinuria and decline in eGFR. One study showed that proteinuria was the strongest correlate of SBP by any BP measurement technique, and this was correlated most closely with both home and ambulatory BP measurements.27 In another study of 77 patients with type 1 diabetic nephropathy who were followed up for 6 years, home BP was a stronger predictor of decrease in GFR than office BP.28 A study from Japan assessed the ability of office versus home BP measurements to predict progression of kidney disease in 113 patients with CKD who were followed up for 3 years. Although both office and home BP readings were correlated significantly with decrease in kidney function as assessed by eGFR, home BP measured in the morning had the strongest correlation with yearly decline in eGFR.29 In a study of elderly patients older than 70 years from Japan with CKD stages 3-5, home BP was measured every morning and evening for 7 consecutive days. Home BP readings were obtained every 6 months for 79 of 104 of these patients, and mean duration of follow-up was 39 months. The study results showed significant correlations between morning SBP, evening SBP, and change in GFR during the follow-up period. Stepwise multivariate regression analysis showed that morning SBP and proteinuria were independent predictors of change in GFR. This study showed that home BP monitoring as compared to office BP is a significant predictor of decrease in kidney function and development of ESRD. However, the study did not find a significant association between office or home BP and risk of death or cardiovascular events.30
A prospective cohort study of 217 veterans with CKD was conducted to assess how well home BP readings predict ESRD and death.31 Patients had home BP measured, ambulatory BP monitoring performed, and BP measured in the clinic by routine and standardized methods. Routine BP was measured as usually done in the clinic, and standardized BP was measured according to a protocol by trained personal. Patients were followed up for a median of 3.5 years. Seventy-five patients experienced the primary combined end point of ESRD or death, and 39 of these patients died prior to starting dialysis therapy. All types of measured SBP significantly predicted ESRD, death, or the combined end point, but routine clinic SBP did not predict death. However, home BP readings were most predictive for each end point. The same cohort also was studied to define the relationship between BP measurement type and combined end point of myocardial infarction, stroke, and all-cause mortality. Average home BP was 147/78 mm Hg, 24-hour ambulatory BP was 134/73 mm Hg, and office BP was 155/85 mm Hg by the standardized method and 145/75 mm Hg by the routine method. A 1-SD increase in SBP increased the hazard ratio of the composite end point by 1.16 for routine BP, 1.57 for standardized BP, 1.66 for home BP, and 1.42 for 24-hour ambulatory BP readings. In comparison to BP measured in the office, home BP was associated more strongly with the composite outcome.32 These studies support the prognostic value of using home BP in patients with CKD to predict target-organ damage, decrease in kidney function, cardiovascular events, and death. Studies in Dialysis In patients on hemodialysis therapy, a U-shaped curve has been observed for the association between SBP and mortality. Patients with the lowest SBP have the highest mortality, and there is a small increase in mortality in patients with very high pre- or postdialysis BP readings.33 Interdialytic BP readings done in dialysis patients outside the dialysis unit have been shown to
Table 1. Studies of Home BP Monitoring in Patients With CKD Study
Country
CKD or HD
Germany
CKD/DN
77
6.2
Decline in eGFR
Japan
CKD
113
3.0
Decline in eGFR
Agarwal & Andersen27
USA
CKD
217
3.5
ESRD, death
Agarwal & Andersen32
USA
CKD
217
3.4
CV events, death
Okada et al30
Japan
CKD
79
3.2
Decline in eGFR and ESRD; no increase in CV events
Alborzi et al18
USA
HD
150
2.0
CV mortality, death
Agarwal42
USA
HD
326
2.4
Death
Rave et al28 Suzuki et al29
N
Follow-up (y)
Outcomes
Abbreviations: BP, blood pressure; CKD, chronic kidney disease; CV, cardiovascular; DN, diabetic nephropathy; eGFR, estimated glomerular filtration rate; ESRD, end-stage renal disease; HD, hemodialysis. Am J Kidney Dis. 2014;63(5):835-842
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predict target-organ damage, including LV hypertrophy and mortality.18,34-38 In an observational study, 101 dialysis patients used daily home BP monitoring to record a total of 20 BP readings over a 1-week period, including measurements of wake-up and night BP readings. BP also was recorded pre- and postdialysis 3 times per week. The relationship between the weekly averaged BP readings and LV hypertrophy and aortic stiffness (reflecting vascular target-organ damage) were assessed.39 The weekly averaged BP readings showed a significant correlation with LV mass index and pulse wave velocity as a marker of aortic stiffness, whereas predialysis BP did not show a positive correlation.35 Another study by the same group in 96 dialysis patients showed that pulse pressures derived from within and outside the dialysis clinic, when averaged over a 1-week period, were predictive of cardiovascular mortality and all-cause mortality.36 In a survey of 150 long-term hemodialysis patients, home BP monitoring had a superior ability to indicate the presence of LV hypertrophy compared with predialysis readings.34 In a longitudinal follow-up to this study, patients with elevated home BP readings also were found to have higher mortality, whereas dialysis clinic readings did not correlate with this outcome. In summary, home BP monitoring is correlated better than office BP with target-organ damage in dialysis patients and has greater value in predicting cardiovascular and all-cause mortality.
THE FUTURE: INTERFACE WITH ELECTRONIC MEDICAL RECORDS As shown in Fig 2, there are several ways in which patient-level BP data can be added to the patient’s health record. The current technologies allow both
blue tooth and direct internet connections to transmit electronic BP data directly to a personalized health record portal. Large electronic medical record systems in the United States have not adapted to this emerging technology; however, it is our hope that market forces will press them into greater responsiveness. The value of direct data entry is that not only can the data be displayed graphically and subjected to a variety of statistical trends, such as average BP or a measure of variability in BP, they also can be aggregated at a provider level for quality metrics that allow a health care professional to see what level of out-of-office BP control is present in his or her population of patients undertaking such measures. Manually entered BP recordings also are of benefit, but electronic BP recordings have the advantage in that they reduce the requirement for staff to enter the data and reduce the potential for transcription errors. As health care systems continue to grow, BP data for a health system can be aggregated and used to train and educate providers and identify outlier patients who could benefit from specific high-BP referrals. Success stories for such use of large volumes of BP data used to manage a health system include the Kaiser Permanente and Veterans Administration Medical Center experiences.40,41
CONCLUSIONS Many patients measure BP outside the office. It is our opinion that home BP monitoring will have an increasingly important role in the management of BP in patients with CKD in the future. We acknowledge that patients with white-coat hypertension have been included in many prior clinical hypertension studies, whereas patients with masked hypertension probably have been excluded from many clinical studies.
Figure 2. Graphic depicts methods for placing out-of-office blood pressure (BP) data into patient records. (Upper panel) The patient is properly positioned, with arm/back/feet supported. The data are kept by the patient, brought to the visit, and then either scanned, copied, or attached to the paper or electronic chart (no portal for direct entry). (Lower panel) The same patient measures BP with a BP device (BPD) that can access directly to the electronic health record (EHR) by an internet portal. The sine wave line shows data uplink. Once part of the EHR, the BP data can be viewed at each visit, tallied, averaged, variability computed, and/or added to a secure database for quality metrics. 840
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Home Blood Pressure Monitoring in CKD
Therefore, we base most of our opinions on studies in which BP has been measured in the office setting. We believe that our role as health care providers should be to encourage home BP monitoring, and this should include oversight of the patient’s technique to ensure that the data are trustworthy, encouraging the use of monitors that have been subjected to validation procedures (see www.dableducational.org for an example of a website that discusses home BP monitor validation), and working with electronic medical record companies to develop and improve patient portals and BP data management and display functions. Exciting developments in the area of BP monitoring include home BP monitors that incorporate blood glucose measurement capability, and also cuffless methodologies that are promising for greater BP data acquisition (including nocturnal values) without the disturbance of cuff inflations (see, eg, the Contipress at www.senseas.com/contipress). One note of caution needs to be stated in closing. Although we are enthusiastic about the ability to gain more information about a patient’s BP pattern by using home BP measurements, there still is a need to show that such knowledge can be translated into true cardiovascular benefit because most prior outcome studies have used office BP readings when assessing BP measurements. At present, the benefits of home monitoring are greater patient empowerment in their care, insight into the connection of BP (and heart rate) with symptoms, and in some cases, better control with less medicine and/or greater attention to lifestyle measures by the patient. In embracing the growing popularity of home BP monitoring, it is important to determine that we truly are benefitting the target organs in the process. We still await the data showing this.
CASE REVIEW Case 1 To ensure the accuracy of the patient’s home BP monitor, he brought in his automated BP device during one of his office visits. While in the office, his home BP monitor and the office BP device showed similarly elevated BP readings of 180-188/60-68 mm Hg. Home BP monitoring was helpful and supported the diagnosis of white-coat hypertension. Further medication adjustments were not needed. Case 2 During subsequent office visits, the patient’s home BP recordings showed less labile BP readings, but more persistent elevation of BP in the range of 150-160/60-70 mm Hg, comparable to her BP readings obtained during the office visits. The furosemide dosage was increased from daily to twice daily and spironolactone was added, and it resulted in reductions Am J Kidney Dis. 2014;63(5):835-842
in both home and office BP to the range of 130-140/6070 mm Hg. Case 3 To ensure accurate home BP readings, the patient brought in her home BP device during an office visit, and the home BP monitor had BP readings similar to the office BP device, supporting the diagnosis of masked uncontrolled hypertension. Amlodipine was added, with further reduction of home BP to the range of 120-130/60-66 mm Hg.
ACKNOWLEDGEMENTS Support: None. Financial Disclosure: The authors declare that they have no relevant financial interests.
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