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Saudi Journal of Kidney Diseases and Transplantation
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Year : 2016  |  Volume : 27  |  Issue : 5  |  Page : 942-949
Hypertension in hemodialyzed children

1 Department of Pediatrics, College of Medicine, Al-Nahrain University, Baghdad, Iraq
2 Imamane Al-Khadhimain Medical City, Baghdad, Iraq
3 Ibn Al-Baladi Teaching Hospital, Baghdad, Iraq

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Date of Web Publication22-Sep-2016


Hypertension (HTN) is one of the most common sequelae of chronic kidney disease (CKD) in children. Dialysis-related HTN is predominantly caused by chronic volume overload, and as such the blood pressure (BP) can be reduced and/or brought down to normal in a sizable number of patients with improved salt and fluid balance. This study was conducted to assess the prevalence of HTN among children on hemodialysis (HD) and to evaluate the correlation of HTN with some demographic data. This is a prospective study performed on forty pediatric patients with CKD receiving maintenance HD in three centers in Baghdad. HTN was defined as BP ≥95 th percentile for age, height, and sex or use of antihypertensive medications. HTN was recorded in 27 patients on HD (67.5%), while the BP was normal in the other 13 patients (32.5%). There was no significant correlation between HTN and gender, age, or etiology of CKD. Duration of the HD session, number of sessions per week, total duration on HD, and blood flow rate also had no statistical correlation with HTN. Only serum albumin showed a significant correlation with BP.

How to cite this article:
Ali SH, Assi SH, Hussien FS. Hypertension in hemodialyzed children. Saudi J Kidney Dis Transpl 2016;27:942-9

How to cite this URL:
Ali SH, Assi SH, Hussien FS. Hypertension in hemodialyzed children. Saudi J Kidney Dis Transpl [serial online] 2016 [cited 2021 Oct 22];27:942-9. Available from: https://www.sjkdt.org/text.asp?2016/27/5/942/190849

   Introduction Top

Hypertension (HTN) is one of the most common sequelae of chronic kidney disease (CKD) in children [1],[2] and is defined as average systolic blood pressure (SBP) and/or diastolic blood pressure (DBP) that is ≥95 th percentile for age, gender, and height on three or more occasions. [3],[4]

The North American Pediatric Renal Transplant Cooperative Study database reported that 64% of patients on hemodialysis (HD) required antihypertensive medication at the initiation of dialysis, and 40% still required medication two years after initiating dialysis. [5] Dialysis-related HTN is predominantly caused by chronic volume overload, and as such the blood pressure (BP) can be reduced and/or brought down to normal in a sizable number of patients with improved salt and fluid balance. [6],[7]

Other contributing factors to HTN include activation of the sympathetic and renin-angiotensin-aldosterone systems, endothelial cell dysfunction, arterial stiffness, exposure to hypertensinogenic drugs, chronic hyperparathyroidism, and electrolyte imbalances during HD. [2],[7]

It is already established that HTN in pediatric HD patients is associated with adverse cardiovascular outcome; therefore, good anti-hypertensive management can substantially contribute to better renal and patient survival of adults with childhood-onset CKD. [7],[8]

   Aims of Study Top

This study was conducted to assess the prevalence of HTN among children on HD and to evaluate correlation of HTN with some demographic data such as age, gender, and etiology of CKD and HD data such as duration on HD, number of sessions per week, hours per session, blood flow rate ( BFR), and type of vascular access. In addition, an attempt is made to see if there is any association of some laboratory parameters such as hemoglobin (Hb), serum calcium (s. Ca), serum phosphorus (s. Ph), and serum albumin with HTN. In addition, the type and number of anti-HTN medications used by the patients were also studied.

   Patients and Methods Top

is a prospective study performed on forty pediatric patients with CKD receiving maintenance HD in three pediatric HD centers in Baghdad: Hamida Al-Musafat HD Center/ Imamane Al-Khadhimain Medical City, AlRahma HD Center/Child Central Teaching Hospital and Ibn Al-Baladi HD Center. The study period was from March 1, 2013, until the end of March 2014.

A four-week data were collected including demographic details such as age, gender, and etiology of CKD. Duration of CKD before HD was not included in this study. The time of data collection was not the same for all patients.

HD data included: duration on HD, number of sessions per week, hours per session, BFR, and type of vascular access. Data pertaining to HTN included: preand post-HD SBP and DBP and the mean value of the preand postHD BP measurements.

HTN was defined as BP ≥95 th percentile for age, height, and sex or use of antihypertensive medications. Pre-HTN was defined as BP ≥90 th percentile but <95 th percentile, without any antihypertensive medications; BP <90 th percentile for age, height, and sex was considered normal or controlled in treated patients. [3],[9] BP was measured by an automated cuff on a dialysis machine. Pre-dialysis BP was obtained for each patient when the patient was sitting on his bed and connected to the machine, just prior to the initiation of HD. Post-dialysis readings were obtained after the completion of rinse back.

Body weight (Bwt) was obtained with the patient standing without wearing shoes on an electronic scale. Ultrafiltration (UF) was calculated from the difference between mean pretreatment weight and mean post-treatment weight and the mean values were recorded. Data of the antihypertensive medications, with respect to the number and type, were collected. Laboratory tests including Hb, s. Ca, s. Ph, and serum albumin were performed and the values were recorded. These values were collected from the monthly routine laboratory investigations performed routinely on all patients. In patients with infections, tests were performed after the infection had subsided.

Normal values were as follows: [9],[10] s erum albumin: 4-5.3 g/dL, s. Ca: 2.2-2.7 mmol/ L, s. Ph: 3.7-5.6 mg/dL, and Hb: ≥11 g/dL.

Dialysis adequacy represented by the urea reduction ratio ( URR) and single pool Kt/V values was calculated. [9],[11],[12]

Hemodialysis single pool Kt/V

The single pool Kt/V values and the URR were calculated using standard formulas. The patients were divided into two groups:

  1. The first group was the hypertensive group: children with BP ≥95 th percentile for age, height, and sex
  2. The second group was the nonhypertensive group: children with BP <90 th percentile, and pre-hypertensive children with BP ≥90th and <95th percentile.

   Statistical Analysis Top

All statistical analyses were made by the Statistical Package of Social Science version 15. The Chi-square was used to compare the groups for the presence or absence of statistically significant differences. The lowest level of significance chosen was when the probability, P ≤0.05, and highly statistical significance was when P ≤0.001.

   Results Top

In this study, HTN was recorded in 27 patients on HD (67.5%), while the BP was normal in the 13 other patients (32.5%). There were more males than females in both the HTN and non-HTN groups (74% and 53%, respectively). Twelve of the HTN patients (44.5%) were older than 12 years Vesicoureteric reflux (VUR) and neurogenic bladder (NB) were the most common causes of CKD which were seen in ten children (37%) in the HTN group, while congenital anomalies were the most common etiology of CRF which were seen in six children (46.2%) in the nonHTN group. VUR and NB were put in a separate category as they could be acquired or congenital and could not be clarified in most of the cases in this study.

Seven patients in the HTN group had CKD due to acquired causes; three had focal and segmental glomerulosclerosis, two of them had renal stones, and two other patients had the hemolytic uremic syndrome. There was no significant correlation between the presence of HTN and gender, age, or etiology of CKD as shown in [Table 1].
Table 1: Patient distribution according to demographic data and relation with hypertension.

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The most commonly used anti-HT drugs were calcium channel blockers (CCB), diuretics, and B-blockers in 24 (89%), 19 (70%), and 18 (67%) patients, respectively, as shown in [Figure 1]. In two patients (7.4%), the BP could be controlled with one antihypertensive drug, five patients (18.5%) required two antihypertensive drugs, 11 patients (40.7%) required three antihypertensive drugs, while in nine patients (33.3%), the BP was controlled with the use of more than three antihypertensive drugs.
Figure 1. Types of antihypertensive drugs received.

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Twenty-one patients with HTN (77.8%) and seven without HTN (53.8%) received three HD sessions per week; the difference was not statistically significant (P = 0.121); also, 15 patients (55.5%) with HTN and six without HTN (46.1%) received two sessions of HD per week; the difference was not significant (P = 0.372). The mean duration on HD was 13.8 ± 13.1 months in 15 patients with HTN (55.6%), while it was 9.8 ± 8.8 months in nine patients (69.2%) without HTN. Again, the difference was not significant (P = 0.610).

In both the HT and non-HTN groups, the BFR was between 100 and 120 mL/min. Moreover, it was observed that more than half of the patients underwent HD through dual lumen catheter (24, 55.5%), while 16 patients

underwent HD with AVF. Dual lumen catheter constituted the main vascular access in 15 patients (55.5%) in the HTN group and nine patients (69.2%) in non-HTN group; however, the P value was not statistically significant.

Pre-HD records showed that all HTN patients (27, 100%) had SBP >95 th centile. Post-dialysis results showed a reduction in SBP; however, 20 of them (74.1%) continued to have SBP >95 th centile; the P value was highly significant (<0.0001; [Table 2]. Similarly, 24 patients (88.8%) with HTN had DBP >95 th centile. Post-HD, 23 patients (85.1%) continued to have DBP >95 th centile (P value was highly significant <0.0001).
Table 2: Patient distribution according to pre- and post-dialysis blood pressure

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Pre-HD mean Bwt of HTN patients was 24.8 ± 9.1 kg, which was more than the weight in the non-HTN group (21.6 ± 7.4 kg). Post-HD, patients with HTN showed slightly lower reduction in mean Bwt (24.1 ± 8.9 kg) than the non-HTN patients; difference was not significant (P = 0.0542).

The majority of HTN patients had lower KT/V and URR, seen in 74% and 66.6%, respectively. The majority of non-HTN patients also had low KT/V and URR, seen in 69.2% and 53.8% of the patients, respectively. The differences were not statistically significant (P value for KT/V = 0.74, P value for URR = 0.43).

A total of 21 (77.7%) HTN patients and 10 (77%) non-HTN patients had low Hb although the difference was not statistically significant. The serum levels of Ca and Ph were not statistically different between the groups with and without HTN.

Serum albumin was low in 15 HTN patients (55.5%), while 11 patients (84.6%) in the nonHTN group had normal levels; difference was statistically significant (P = 0.016; [Table 3].
Table 3: Patient distribution according to laboratory investigations.

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   Discussion Top

This cross-sectional study of forty pediatric HD patients shows an exceptionally high prevalence of HTN in our study population. This compares with an estimated prevalence of HTN of 2-5% in the general pediatric population, a prevalence of 54% in pediatric patients with stage 1-3 CKD, and a prevalence of 65% in pediatric and young adult HD patients. [13],[14] Two recent studies have shown that HTN values were present in 79% and 67.9%, respectively of children on HD. [15],[16] These data show that HTN is common in pediatric long-term HD patients.

In this study, the prevalence of HTN was greater among males than females, consistent with findings in adults. [17],[18] The mechanisms responsible for this gender differences in BP levels are not clear although the interactions between sex hormones and the kidneys are speculated to play a role. [19]

The Task Force Report and other studies demonstrate that age is a major determinant of BP. [3],[20] BP increases progressively with age and more rapidly during puberty. [20],[21] The prevalence of HTN also increases progressively with age. [22] In contrast, Halbach et al, in their study, found that young age is a risk for HTN. [15] Two recent studies have reported that glomerular and acquired kidney disease constitute a risk for HTN. [15],[16] This difference from our results may be related to ethnicity, higher rate of urinary tract infection among our population. It was estimated that the most common form of renal parenchymal disease associated with HTN is pyelonephritic scarring. [23]

Two big studies have shown that calcium channel blockers are more efficacious than beta-blockers in reducing the risk of stroke, substantially lower risks of total (21%) and cardiovascular (26%) mortality, [24] but that they are less efficacious in reducing the risk of cardiac ischemia. [25]

The association of greater antihypertensive drug use with improper control of HTN may be related to fluid overload, which makes HTN difficult to control despite the use of antihypertensive drugs. [26]

Two studies have shown that patients on long-term regular HD had better response and lesser HTN and cardiovascular events than nondialyzed patients. [27] The dialysis procedure can lend itself to treatment with the use of a low-sodium dialysate, sodium profiling, or daily dialysis. [28] With increased blood flow, more solute is delivered to the dialyzer resulting in higher dialyzer clearance. [29] HTN was more prevalent in those dialyzed with AVF, which is a well-known risk factor for HTN and cardiovascular diseases. [30]

Minimal improvements in BP readings were seen post-HD in our patients. These findings are significantly higher than the European data reported more than a decade ago by Loirat et al [31] in which only 15% of pediatric HD patients remained hypertensive immediately following HD and comparable to a study by VanDeVoorde et al, [32] which showed that more than 65% of patients still had HTN. Volume overload, inadequate dosing of the antihypertensive drugs, and less compliance with sodium restriction were the probable causes of HTN among our patients.

A previous study found no significant difference in hematocrit levels between normotensive and hypertensive dialysis patients. [32] However, two other studies reported that lower mean Hb values were associated with HTN. [16],[33] Marchais, et al reported that a significantly higher serum phosphorus level was found among hypertensive patients. [34] Etiologic theories suggest that hyperphosphatemia contributes to the secondary hyperparathyroidism and increased calcium entry to vascular wall smoothmuscle cells. [35] In vitro studies have found increased calcification with dose-dependent phosphate levels. [36]

Chavers et al correlated lower Ca values with HT. [16] No correlation between HTN and serum Ca levels was found in our patients. The correlation reported between lower serum albumin and poor HTN control may be because of inflammation, malnutrition, and wasting that culminates in subtle, unrecognized, and fluid excess and has been reported in a study from India. [37]

   Conclusion Top

Majority of the pediatric patients in this study were hypertensive. There was no significant correlation between HTN and gender, age or, etiology of CKD. This study emphasizes the difficulty of BP control in pediatric HD patients as most of them need more than three drugs to control their BP. Duration of the HD session, number of sessions per week, total duration on HD, and BFR had no statistical correlation with HTN. Only serum albumin showed a significant correlation with BP.

   Acknowledgment Top

Authors would like to express their gratitude and appreciation to all medical staff at the four dialysis centers, aforementioned, for their help and cooperation in making this study possible.

Conflict of interest: None declared.

   References Top

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Correspondence Address:
Shatha Hussain Ali
Department of Pediatrics, College of Medicine, Al-Nahrain University, P. O. Box 70074, Baghdad
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DOI: 10.4103/1319-2442.190849

PMID: 27752002

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