Arterial Hypertension in Dialysis Patients: Impacts of Age, Gender, Dialysis Characteristics and Etiologies of Chronic Kidney Diseases

  

    
Characteristics 
    
HD1 cases (N/%) 
      
(38 ;49.4 ) 
    
CAPD2 cases (N/%) 
      
(39; 50.6 ) 
    
Total number 
  
  

    
Age group 
      
= 12 months
      
1-5 years
      
6-10 years
      
11-16 years
      
>16 years
    
 
      
0
      
2(10)
      
5(50)
      
11(61.1)
      
20(90.9)
    
 
      
7(100)
      
18(90.)
      
5(50)
      
7(38.9)
      
2(9.1)
    
 
      
7
      
20
      
10
      
18
      
22
  
  

    
Gender 
      
Male
      
Female
    
 
      
21(55.2)
      
17(44.8)
    
 
      
21(53.8)
      
18(46.2)
    
 
      
42
      
35
  
  

    
 
      
History of transplantation 
      
Yes
      
No
    
 
      
 
      
6(15.8)
      
32(84.2)
    
 
      
 
      
2(5.1)
      
37(94.9)
    
 
      
 
      
8
      
69
  
  

    
Urine output status3 
      
Anuria
      
Non anuria
    
 
      
8(57.1)
      
25 (43.9)
    
 
      
6(42.9)
      
32 (56.1)
    
 
      
14
      
57
  
  

    
Mean systolic blood pressure (at the time of    study )
      
Normal
      
Prehypertension
      
Hypertension
    
 
      
17(36.2)
      
6(75)
      
15(68.2)
    
 
      
30(63.8)
      
2(25)
      
7(31.8)
    
 
      
47
      
8
      
22
  
  

    
Mean diastolic blood pressure (at the time of    study )
      
Normal
      
Prehypertension
      
Hypertension
    
 
      
19(50)
      
6(15.8)
      
13(34.2)
    
 
      
26(66.7)
      
5(12.8)
      
8(20.5)
    
 
  
  

    
Main     etiologies of CKD 
      
VUR
      
Glomerulopathies
      
Renal dysplasia
      
Idiopathic
    
 
      
16(50 )
      
7(53.8 )
      
0(0)
      
10(62.5 )
    
 
      
16(50 )
      
6(46.2)
      
7(100)
      
6(37.5)
    
 
      
32
      
13
      
7
      
16
  
  

    
Total hypertensive cases4
    
20(52.6)
    
18(46.2)
    
38
  
  

    
1) Hemodialysis 2) Continuous    ambulatory peritoneal dialysis 3) Urine output status in 6 cases were not    clear 4) All case with arterial hypertension and also including those who    have receiving anti-hypertensive medication and had normal blood pressure at    the time of the study 
      
 
  

Table 5: Comparing clinical and dialysis characteristics in hypertensive versus non-hypertensive cases.

Discussion

Hypertension is one of the most preventable causes of death and morbidity in CKD cases. The prevalence of hypertension is high in adult patients with CKD (87–90%) [11], in a study the prevalence of complications that occurred in children with CKD were assessed [12]. The study and 4 patients (5.2%) who didn’t receive antihypertensive.

Hypertension was the most common complication in all five stages of CKD (70.2%). Recent data from USA indicate that about 38% of children with CKD in the United States are receiving antihypertensive therapy [13]. In our cases which include patients with CKD stage 5, 34 patients (44.2%) were on antihypertensive therapy at the time of drugs needed these medications. Toto reported a prevalence of 80% for hypertension in adults with CKD [2]. In our series 12 cases (15.6%) were adult patients (>18 years), their ages were 18yr and 4 months up to 25 yr (mean 20 yr and ten months). Six of adults (50% of adult cases) had arterial hypertension and were on anti-hypertensive medications.

Children with certain underlying diseases like glomerular and polycystic kidney disease, are more prone to develop hypertension [14,15]. Inappropriate normal renin levels with considering the degree of hypertension and volume overload [16,17], sodium retention and hyperreninemia in cases with renal cysts and scars, microangiopathic lesions or tubulointerstitial inflammation [18,19] are factors participating in pathogenesis of hypertension in CKD. Residual urine output has been reported lower in hypertensive children on dialysis rather than their normotensive peers [15]. This finding and lowers mean blood pressure after nephrectomy despite causing anuria [20] point to presence of important volume independent factors for blood pressure regulating in HD patients. Increase in both plasma renin activity and catechol amines after HD were suggested as important factors in pathogenesis of hypertension in CKD [21].

Dietary sodium restriction, improve dialysis prescription and pharmacological treatments are main therapeutic approaches to hypertension in CKD [22]. Regression of end-organ damage (especially left ventricular hypertrophy ), lowering of blood pressure below target values with minimal drug side effects are the aims of antihypertensive therapies. A blood pressure of <130/80mmHg in adults [23,24], and <90^th percentile in children [25] are recommended as goals of antihypertensive treatments in CKD.

Control of extracellular volume is a key parameter for reducing the arterial hypertension. Plum et al. [26] compared body fluids distribution between HD and PD adults by using some biophysical and biochemical methods. They found that total body water is increased in PD patients. In addition they showed links between extracellular expansion and elevated systolic blood pressure. Clinical signs of over hydration were significantly more common in PD versus HD cases (87.5±35.3% versus 53.9±50.8%), and systolic blood pressure was significantly higher in PD cases than HD patients (162±21 versus 148±30). In contrast to their findings we found higher prevalence of arterial hypertension in HD compared to CAPD cases (52.6% versus 46.2%) (P= 0.57) (Table 5).

During the first few months or years of dialysis, while residual renal function (RRF) and diuresis are maintained, PD patients usually provide better fluid and blood pressure control than HD [27-29] probably due to better saving the urine output, continuous ultrafiltration or better clearance of vasopressor toxins [30]. Several years after starting PD, the prevalence of hypertension increases in PD cases as a result of progressive loss of RRF and decreased peritoneal membrane capabilities [31-34]. Our findings in HD and CAPD patients didn’t confirm such association between time from onset of dialysis and prevalence of arterial hypertension. In overall prevalence of hypertension one and 2-5 years after onset of dialysis in CAPD cases were 52.9% and 40% respectively and just 2 cases were placed on dialysis from >5 years ago who had a normal blood pressure without using antihypertensive medications (P=0.483). In contrast to previous reports [31-34] our CAPD cases had reached a better blood pressure control with increasing time from onset of dialysis.

In HD cases who were placed on dialysis from = 1yr, 2-5 yr and >5 yr, the prevalence of arterial hypertension were 63.6%, 69.2% and 33.3% respectively (P=0.217). Unlike other reports [27-29] HD patients who were received dialysis from more than 5 years had the lowest prevalence of hypertension. This trend of changes in prevalence of hypertension was not related to changes in urine output. With increasing the time from onset of dialysis in HD cases, the anuria condition gradually increased as in first year of hemodialysis 10%, in 2-5 years of dialysis 23% and after 5 years 33% of HD cases reached anuria condition, while the highest prevalence of hypertension was found in those who were dialyzed from 2-5 years ago, and those who were placed on HD from >5 years ago had the lowest prevalence of hypertension.

In CAPD cases prevalence of anuria didn’t change significantly 2-5 years after onset of dialysis (15%) compared with first year of dialysis (17.6%). We didn’t measure the RRF in cases without anuria. What were the reasons for these paradoxical changes in urine output with increase in time from onset of dialysis in CAPD subjects? It’s not clear.

Prevalence of hypertension in our cases (patients with CKD stage V) was 2/3 of that reported by Wong et al. (who consisted of different stages of CKD) [8]. This finding was surprising since it was expected that in end stage renal failure (CKD stage V) which is associated with the highest decrease in glomerular filtration rates (GFR), signs of sodium retention and fluid overload increase. This difference in prevalence of hypertension in our subjects compared with patients evaluated by Wong et al. may be related to higher frequency of glomerular disorders in their cases compared with our patients (27.2% versus 14.3%).

Higher frequency of hypertension in subjects with glomerular disorders was completely expected since volume overload due to decreased GFR and increased activity of renin–angiotensin aldosterone system which are accompanying glomerular diseases results to sodium retention and finally lead to arterial hypertension. Why hypertension was more frequent in those who recently were placed on dialysis? One explanation might be that dialysis either HD or PD remove sodium and water effectively and help to prevent volume overload which finally leads to decrease in blood pressure, thus cases who were receiving dialysis recently and were hypertensive gradually change to normotensive cases.

In contrast to HD which is an intermittent procedure, CAPD is a continuous treatment of uremia and may be more advantageous for blood pressure regulation. Prevalence of hypertension is considerably lower in peritoneal dialysis patients [35]. In our cases although arterial hypertension was more prevalent in HD subjects versus CAPD cases (52.6% versus 46.2%), the difference was not significant (P=0.57). In the ESRD Core Indicators Project of 1219 CAPD patients 26% had systolic and 16% had diastolic hypertension [36]. In our study of 39 CAPD cases, 18 cases (46.2%) had histories of systolic and diastolic hypertension and were receiving anti-hypertensive drugs. At the time of study systolic blood pressures were normal in 30(76.9%) subjects including 11 cases on anti- hypertensive medications, and were in prehypertension and hypertension ranges in 2 (5.1%) and 7 (18%) cases respectively. Diastolic blood pressures were in normal, prehypertension and hypertension ranges in 26 (66.7%), 5 (12.8%) and 8 (20.5%) patients respectively. A similar extended study in HD cases [37] showed that before placing on dialysis prevalence of hypertension was considerably higher in HD than CAPD subjects, but after starting the dialysis the prevalence of arterial hypertension was comparable between 2 groups. In our cases of 19 HD patients who despite anti-hypertensive medications at the time of study had high systolic or diastolic blood pressures, 6 (31.6%) were placed on dialysis from = 1 years, whereas 13 cases (68.4%) were receiving HD from >1 year ago (P=0.831). In CAPD population of 7 cases who despite anti-hypertensive treatments had high blood pressures, 3 (42.9%) were placed on dialysis from = 1 year and 4 (57.1%) were receiving PD from > 1 year (P=0.791).

The main limitation of the study was that monograms of systolic and diastolic blood pressures in USA children were used for definition of normal blood pressure, prehypertension and hypertension. Unfortunately standard published monograms blood pressures in Iranian children were not accessible.

Conclusion

We found that arterial hypertension is a common complication of CKD stage 5 (49. 3%). The highest and lowest prevalence of hypertension were seen in school aged children (6-10 years; 80%) and early years of teenager period (11-16 years; 33.3%) respectively. In addition we found it’s as common in children as young adults, and hemodialysis as CAPD patients. Patients with glomerular diseases and those who recently were placed on dialysis are more prone to develop hypertension. Hypertension is as prevalent in cases with anuria as those without. It is not affected by hours of dialysis weekly in HD cases and also dialysis solution volume applied per day (cc/kg/ day) in CAPD cases. In addition HD cases on standard dialysis (12 hours weekly) are affected by arterial hypertension as cases with lower weekly dialysis doses (<12 hours weekly). Absence of significant effects of dialysis characteristics on prevalence of hypertension suggest that may be renin dependent factors are more important in pathogenesis and maintaining high arterial blood pressure in dialysis cases.

Absence of significant effects of dialysis characteristics on prevalence of hypertension suggest that renin dependent factors are more important in pathogenesis and maintaining high arterial blood pressure in dialysis cases, Thus it seems that ACEI medications should be considered as first line antihypertensive drugs in treatment of hypertension in dialysis subjects. Whether using ACEI medications as first line of treatment instead of loop diuretics can improve BP control in dialysis cases (those with and without anuria) is a good question that should be answered by more studies.

Acknowledgement

The author would like to appreciate Dr. Esmaeeli, Dr. Ghaneh and Dr. Azarfar (pediatric nephrologists) for their advocated helps.

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