|Year : 2020 | Volume
| Issue : 2 | Page : 196-201
Target blood pressure in patients with chronic kidney disease on maintenance hemodialysis using ambulatory blood pressure monitoring for 72 h – A prospective observational study
Vishal Mangal1, Ranjith Nair2, Kaminder Bir Kaur3, Sachin Maggo1
1 Department of Internal Medicine, Army Hospital Research & Referral, New Delhi, India
2 Department of Nephrology, Army Hospital Research & Referral, New Delhi, India
3 Department of Anaesthesiology & Critical Care, Army Hospital Research & Referral, New Delhi, India
|Date of Submission||19-Jul-2020|
|Date of Decision||31-Aug-2020|
|Date of Acceptance||28-Sep-2020|
|Date of Web Publication||23-Dec-2020|
Dr. Vishal Mangal
Department of Internal Medicine, Armed Forces Medical College, Pune - 411 040, Maharashtra
Source of Support: None, Conflict of Interest: None
Background and Aim: The target blood pressure (BP) in CKD patients on hemodialysis (HD) remains a dilemma. We aimed to study the BP value most representative of the presence or absence/control of hypertension in CKD patients on HD, and how well could ambulatory BP monitoring (ABPM) predict the presence of hypertension. Materials and Methods: A total of 39 patients with CKD on twice-weekly HD were included in the study. BP was recorded with the help of the sphygmomanometer installed in the HD machine at regular intervals, and the same was compared with ABPM continuously for 72 h during the interdialytic period. Bland–Altman analysis and receiver operating characteristic curve were analyzed. Results: The difference between the mean predialysis systolic blood pressure (SBP) and mean ambulatory SBP was 9.09 mmHg (95% confidence interval [CI], -22.92 to + 41.099 mmHg); however, the difference of 4.86 mmHg (95% CI, -17.886 to + 27.606 mmHg) between the mean diastolic ABPM reading and the mean predialysis diastolic BP did not achieve significance. Conclusion: The data suggest that predialysis office SBP invariably overestimates BP and should not be targeted as a BP goal, as it could lead to intradialytic hypotension. For any given SBP, the postdialysis value is more specific in diagnosing hypertension, thereby reflecting a more significant cardiovascular load. To our knowledge this is the first study to use ABPM continuously during the interdialytic period for 72 h.
Keywords: 72 h, ambulatory blood pressure monitoring, chronic kidney disease, hemodialysis, target blood pressure
|How to cite this article:|
Mangal V, Nair R, Kaur KB, Maggo S. Target blood pressure in patients with chronic kidney disease on maintenance hemodialysis using ambulatory blood pressure monitoring for 72 h – A prospective observational study. Arch Med Health Sci 2020;8:196-201
|How to cite this URL:|
Mangal V, Nair R, Kaur KB, Maggo S. Target blood pressure in patients with chronic kidney disease on maintenance hemodialysis using ambulatory blood pressure monitoring for 72 h – A prospective observational study. Arch Med Health Sci [serial online] 2020 [cited 2021 Mar 9];8:196-201. Available from: https://www.amhsjournal.org/text.asp?2020/8/2/196/304712
| Introduction|| |
The prevalence of chronic kidney disease (CKD) is increasing world over, due to an increase in life expectancy and an increasing prevalence of lifestyle diseases. In the Western world, hypertension and diabetes mellitus are responsible for nearly 60%–70% of the cases of CKD. In India too, hypertension and diabetes mellitus account for around 2/3rd of the cases of CKD.,,, Cardiovascular disease is the main cause of morbidity in patients with CKD Stage 5, and it accounts for nearly 50% of deaths (Kidney Disease Outcomes Quality Initiative guidelines). Not surprisingly, there is inadequate data available from India on the prevalence of CKD.
There are currently no guidelines for the ideal blood pressure (BP) to be maintained in patients on maintenance hemodialysis (HD). BP control in CKD patients on HD remains a vexing problem due to various reasons such as the lack of any specific target values, the variability in BP in between the HD sessions, diet restriction, and drug and fluid compliance. A large number of studies have been conducted to find out the most favorable BP during the interdialytic period. However, their results have been variable. Some studies documented that the predialysis BP measurement taken by the dialysis center technician is more important, while others showed that postdialysis BP is more representative. A few studies have also shown that a combination of both pre-HD and post-HD BP, or even BP taken 20-min after the end of HD is more valuable in predicting hypertension in this group of patients. Coomer et al. found that predialysis and postdialysis BP (recorded by dialysis center technician) had a significant correlation with mean BP; however, predialysis systolic blood pressure (SBP) was on an average 10 mmHg higher than the mean SBP, whereas postdialysis SBP was on an average 7 mmHg lower than the mean SBP. Studies by Mailloux and Levey showed that “all BPs are important,” however, the most favorable BP measurement to use has never been identified. The conflicting literature has created a lot of confusion in the minds of practicing clinicians as to which BP to treat: BP taken by the dialysis center technician before HD, after HD, or a combination of the two.
Our study was an attempt to answer these vexing questions such as which BP values should be targeted for treating hypertension, which BP values are most characteristic of hypertension control in CKD patients on maintenance HD, and how well could ambulatory BP monitoring (ABPM) predict the presence of hypertension as compared to the in-unit pre- and post-HD BP values.
| Materials and Methods|| |
The aim was to carry out a prospective analysis of the role of ambulatory BP measurement in CKD patients on maintenance HD.
The objective was to compare the mean BP recorded immediately pre- and post HD during the two dialysis sessions, with the BP values seen on ABPM with respect to:
- Mean SBP on day 1 of ABPM
- Mean SBP on day 2 of ABPM
- Mean SBP on day 3 of ABPM
- Mean diastolic BP (DBP) on day 1 of ABPM
- Mean DBP on day 2 of ABPM
- Mean DBP on day 3 of ABPM
- 72 h mean SBP by ABPM
- 72 h mean DBP by ABPM
- Relation between weight gain and BP
- Night dipping status
- Relation between weight gain and night dipping status.
This study was an prospective observational study and carried out at a tertiary care hospital in Northern India over a period of 2 years (from November 2016 to November 2018) after due clearance from the institutional ethical committee.
Patients who had CKD and underwent twice-weekly maintenance HD at our center were screened. Only the patients who fulfilled the inclusion criteria were included in the study. A CONSORT diagram showing participant flow in this observational study is shown in [Figure 1].
|Figure 1: CONSORT diagram showing par ticipant flow in this observational study|
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- Patients more than 18 years of age
- Diagnosed cases of CKD irrespective of the underlying pathology
- On maintenance HD for >3 months.
- Age <18 years
- On HD for <3 months
- Patients who did not gave informed written consent.
Each patient was on HD twice a week for 4-h duration (per session). BP was recorded with the help of the sphygmomanometer installed in the HD machine before the start of dialysis; at 1, 2, and 3 h of initiation of dialysis; and finally at the end of the dialysis. The ABPM device was applied to each patient for 24 h at a time and repeated for the next 3 days. It was taken off only prior to the start of the next dialysis session. ABPM data were analyzed with the help of Hypertension Diagnostics Suite software (Tiba Medical, Oregon, Portland, USA).
ABPM was performed continuously for 72 h during the interdialytic period using the Ambulo 2400 ABPM machine (Welch Allyn, Skaneateles Falls, NY, USA). The monitor recorded BP every 30 min during the day and every 60 min during the night. ABPM was started at the end of the first dialysis, and it was removed prior to the next dialysis session.
The daily data obtained were collected as per the regular format. The highest SBP and DBP and the lowest SBP and DBP were recorded, from which average SBP and DBP values were calculated.
Descriptive analysis was done using mean and standard deviation (SD) for continuous variables and frequency and percentages for categorical variables. The data were collected and compiled on Microsoft Excel version 2019, and Statistical software SPSS (version 17, SPSS Inc., Chicago, IL, USA) was used for statistical analysis.
The study was approved by the institutional ethics committee vide certificate number IEC registered no. 72/2016. Informed written consent was taken from all the patients before inclusion in the study.
| Results|| |
A total of 39 patients with CKD were enrolled in the study, with 32/39 (82%) being males. The mean body mass index (BMI) of the patients was 20.69 ± 3.26 kg/m2. Out of the 39 patients enrolled in the study, 26/39 (66.7%) were in the healthy BMI range, 10/39 (25.6%) of the study population were underweight, and 3/39 (7.7%) of the study population were overweight. The mean age of the patients was 38.10 ± 13.71 years, with two patients aged <20 years and four patients aged >60 years. In the study, 13/32 (40.6%) males were in the age group of 31–40 years and 3/7 (42.9%) females were in the age group of 51–60 years.
Among the 39 patients, the cause of CKD was proved histopathologically by renal biopsy in 10 patients (25.64%), which showed etiologies such as IgA nephropathy (7/39 [18%]), diabetic nephropathy (1/39 [2.56%]), focal segmental glomerulosclerosis (1/39 [2.56%]), and graft rejection (1/39 [2.56%]). In the remaining 29 patients, renal biopsy was not attempted as they had bilateral shrunken kidneys at presentation. These unproven patients, based on anemia, hypertension, edema, and urinary disturbances, were grouped into those with chronic glomerulonephritis (16/29 [55.17%]) and those with chronic interstitial nephritis (13/29 [44.83%]). The mean duration of HD in the study population was 6.32 months (minimum – 3 months, maximum – 20 months). A total of 12/39 (30.76%) patients required two or less antihypertensive medications, 24/39 (61.55%) patients required three to four antihypertensive medications, and 3/39 (7.69%) patients required five antihypertensive medications for BP control. As an institutional protocol, the second antihypertensive was added once the full dose of the first had been achieved.
On analysis, it was found that the mean SBP was significantly lower on ABPM recordings as compared to pre-HD SBP recorded by the sphygmomanometer installed in the dialyzer machine. The maximum difference was on day 1 (mean SBP on ABPM was 10.34 mmHg lower than the mean pre-HD SBP, P < 0.007), and this difference narrowed on subsequent days [Table 1]. The difference between the mean pre-HD SBP and mean of 72 h ABPM SBP was 9.09 mmHg (95% confidence interval [CI], -22.92 to +41.099 mmHg). The difference between the mean SBP by ABPM for 72 h and the mean pre-HD SBP was significant. The mean DBP by ABPM was lower than the mean pre-HD DBP by 5.21 mmHg (P = 0.050) on day 1, 4.9 mmHg (P = 0.073) on day 2, and 4.46 mmHg (P = 0.086) on day 3. There was no significant difference between the mean pre-HD DBP and the mean ABPM DBP on any of the days during the interdialytic period [Table 2]. The difference of 4.86 mmHg (95% CI, -17.886 to + 27.606 mmHg) between the 72 h mean ABPM DBP and mean pre-HD DBP did not achieve significance.
|Table 1: Comparison of mean prehemodialysis systolic blood pressure and mean systolic blood pressure on ambulatory blood pressure monitoring|
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|Table 2: Comparison of mean prehemodialysis diastolic blood pressure and mean diastolic blood pressure on ambulatory blood pressure monitoring|
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There was a significant difference between the mean post-HD SBP and the mean SBP by ABPM on the days during the interdialytic period. The maximum difference was on day 1 (mean SBP by ABPM was 15.93 mmHg lower than the mean post-HD SBP). And, this difference narrowed on subsequent days [Table 3].
|Table 3: Comparison of mean posthemodialysis systolic blood pressure and mean systolic blood pressure on ambulatory blood pressure monitoring|
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There was a significant difference between the mean post-HD DBP and the mean DBP by ABPM on all the interdialytic days. The maximum difference was on day 1 (mean DBP by ABPM was 8.57 mmHg lower than the mean post-HD DBP). And, this difference narrowed on subsequent days [Table 4]. In the present study, the mean pre-HD weight was 60.65 ± 9.86 kg, and the mean post-HD weight was 59.01 ± 9.53 kg. The mean weight gain between two dialysis treatments was 1.64 ± 1.06 kg.
|Table 4: Comparison of mean posthemodialysis diastolic blood pressure and mean diastolic blood pressure on ABPM|
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In the present study, on day 1 of ABPM, 28/39 (71.8%) patients were nondippers and 8/39 (20.5%) patients witnessed nocturnal dipping in SBP within the first 24 h immediately after dialysis. On day 2, 23.1% of the patients witnessed a nocturnal dip in the SBP and 64.1% of the patients did not experience any nocturnal dip in the SBP. The number of patients experiencing a nocturnal dip in SBP reduced from 23.1% on day 2 to 17.9% on day 3. Bland–Altman analysis of the pre-HD and mean ABPM systolic and diastolic readings is depicted in [Figures 2] and [Figures 3], respectively.
|Figure 2: Bland–Altman analysis of the predialysis and average ambulatory blood pressure monitoring systolic readings. Reference lines indicate the mean difference of the two methods and their limits of agreement (±2 standard error from the mean differences)|
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|Figure 3: Bland–Altman analysis of the predialysis and average ambulatory blood pressure monitoring diastolic readings. Reference lines indicate the mean difference of the two methods and their limits of agreement (±2 standard error from the mean differences)|
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| Discussion|| |
The present study was a prospective observational study conducted on 39 patients with CKD on maintenance HD at a tertiary care hospital. The study was conducted over a period of 24 months – 3 months of preliminary actions, 18 months of data collection, and 3 months of data analysis with write-up. This study aimed to evaluate the correlation between predialysis office BP and interdialytic ABPM BP along with its relation to interdialytic weight gain and predialysis SBP besides the nocturnal dipping status.
The Bland–Altman analysis [Figure 2] and [Figure 3], which is an analysis of agreement, showed that there was a poor agreement between ambulatory BPs and HD-unit BPs. The average of the BPs was plotted against the difference, and the average difference (bias, shown by the horizontal solid line) and the limits of agreement (±2 SD, shown by the top and bottom horizontal lines) was calculated. We interpreted our data to mean that although HD-unit BPs can be used to detect the presence or absence of hypertension, these measurements cannot be used to accurately comment upon the actual pressures of the individual, which were usually lower in the systolic range. We could also assume that if the ultrafiltration or antihypertensive drug dosing was tailored to the predialysis-unit SBP, there could be an increased incidence of intradialytic hypotension.
In the present study, 72 h mean SBP by ABPM was 9.09 mmHg lower than the mean pre-HD SBP and 72 h mean DBP by ABPM was 4.86 mmHg lower than the mean pre-HD DBP. Similar results were shown by Conion et al. in their study of forty end-stage renal disease patients using ABPM for 24 h. In their study, the mean SBP by ABPM was 4.7 mmHg below the pre-HD SBP and the mean DBP by ABPM was 3.7 mmHg below the pre-HD DBP.
In our study, the mean post-HD SBP was on an average 5.59 mmHg higher than the mean post-HD SBP and 14.68 mmHg higher than the 72 h mean SBP by ABPM. However, the mean post-HD DBP was on an average 3.98 mmHg higher than the mean pre-HD DBP and 8.22 mmHg higher than the 72 h mean DBP by ABPM. Similar observations have been made by Rahman et al. who noted that in 55% of the patients, the immediate postdialysis SBP was at least 10 mmHg higher than the standard reading. These results corroborate with those of Mitra et al. who have shown that BP values taken 20 min after the HD may be the best predictor of hypertension in HD patients.
During the interdialytic period, the average ABPM BP rose sequentially with each day. The mean SBP by ABPM on day 3 was higher than that on day 2 (SBP 140.32 vs. 139.15 mmHg, respectively) and the mean SBP by ABPM on day 2 was higher than that on day 1 (SBP 139.15 vs. 137.87 mmHg, respectively). However, this rise did not show any statistically significant difference.
The mean weight gain between the two dialysis treatments was 1.64 ± 1.06 kg. There was no correlation between 72 h mean SBP/DBP by ABPM, pre-HD SBP or DBP, nocturnal dipping of SBP, and interdialytic weight gain during the period when the ABPM was worn. These findings were consistent with the observations of Kooman et al. and Rodby et al., who were also unable to find any correlation between weight gain during the interdialytic period and an increase in BP during the same period.
There was no correlation between the cause of CKD, duration of dialysis, number of antihypertensive medications, and the BP in the present study.
A large number of studies have tried to address this question, of which BP is most characteristic of the interdialytic BP., Some studies documented that the pre-HD BP taken by the dialysis center technician was more important,, while others showed that post-HD BP was more representative. A few studies also showed that a combination of both pre-HD and post-HD BP, or even BP taken 20-min after the end of HD was more valuable in predicting hypertension. We used the receiver operating characteristic (ROC) analysis to plot the true-positive rate (TPR) against the false-positive rate (FPR), with TPR on the y-axis and FPR on the x-axis [Figure 4] and [Figure 5]. A worthless test would fall along the diagonal line, that is, the FPR would increase with a TPR. An ideal test would have 100% sensitivity and 100% specificity for a given result. An excellent model has area under the curve (AUC) near to 1, which means it has a good measure of separability, whereas a poor model has AUC near to 0, which means it has the worst measure of separability. It means it is reciprocating the result. The AUC of ROC curves of 80% or more for any BP strongly supports the observations of Mailloux and Levey that “all BPs are important.”
|Figure 4: Receiver operating characteristic curve of hemodialysis unit systolic blood pressures and the presence or absence of hypertension as defined by ambulatory blood pressure monitoring|
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|Figure 5: Receiver operating characteristic curve of hemodialysis-unit diastolic blood pressures and the presence or absence of hypertension as defined by ambulatory blood pressure monitoring|
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It is essential to bear in mind that the cutoff values to diagnose hypertension in patients on HD are different when pre-HD BP values are taken and different when post-HD BP values are taken.
In our study, pre-HD SBP >135 mmHg had 84.4% sensitivity and 57.1% specificity with 90% positive predictive value and accuracy of 79.5% in diagnosing hypertension in CKD patients on maintenance HD [Table 5]. Because of the wide range of limits of agreement, the absolute level of ambulatory BP cannot be predicted with confidence from HD-unit BP measurements.
|Table 5: Accuracy analysis of pre- and post-hemodialysis blood pressure with ambulatory blood pressure monitoring|
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Our study had few strengths such as it is the first study to use ABPM for 72 h and continuously during the interdialytic period to establish the representative BP in CKD patients on HD. However, there were some limitations such as the sample size was small and the effect of antihypertensive medication was not evaluated.
| Conclusion|| |
It can be clearly concluded that the predialysis office SBP invariably overestimates the BP in dialysis patients, and it should not be targeted as a BP goal, as it could lead to intradialytic hypotension and further worsen cardiovascular outcomes. It would be advisable to record the BP at least 20 min after the cessation of dialysis for the values to be representative. For any given SBP, postdialysis hypertension is more specific in diagnosing hypertension and therefore reflects a more significant cardiovascular BP load as compared to predialysis hypertension. This study is the first one to use ABPM for 72 h during the interdialytic period. This will open up a new path for further research in establishing the target BP in CKD patients on HD and also the timing to record BP for targeting the antihypertensive treatment.
We would like to thank all the staff at the dialysis center without whose help this project would not have been possible.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]