Perit Dial Int
29(Supplement_2):
15-17
2009
© 2009 International Society for Peritoneal Dialysis
Part 1: Calcium and Phosphorus Metabolism in Peritoneal
Dialysis |
THE INFLUENCE OF DIALYSATE CALCIUM ON PROGRESSION OF ARTERIAL STIFFNESS IN PERITONEAL DIALYSIS PATIENTS
Meltem Sezis Demirci,
Mehmet Ozkahya,
Gulay Asci,
Ebru Sevinc,
Mumtaz Yilmaz,
Cenk Demirci,
Huseyin Toz,
Ali Basci and
Ercan Ok
Division of Nephrology, Ege University School of Medicine, Izmir,
Turkey
Correspondence to: M.S. Demirci, Ege University School of Medicine, Division
of Nephrology, 35100 Bornova, Izmir, Turkey.
meltem.sezis{at}ege.edu.tr,
meltemsez{at}hotmail.com
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ABSTRACT
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Background: One of the origins of cardiovascular
disease in dialysis patients is arterial stiffness. The aim of our study was
to assess the relationship between the calcium content of peritoneal dialysis
(PD) solution and arterial stiffness.
Patients and Methods: We enrolled into the study 49 PD
patients who had been treated with the same PD solution for the preceding 6
months. The calcium content of the PD solution was 1.25 mmol/L in 34 patients
(low-Ca group) and 1.75 mmol/L in 15 patients (high-Ca group). Study patients
were followed for 6 months on the same PD prescription. Arterial stiffness was
assessed by measurement of augmentation index (AI) and brachial pulse wave
velocity (PWV) at baseline and at month 6 (SphygmoCor: Atcor Medical, West
Ryde, NSW, Australia). Demographic data were recorded from patient
charts.
Results: Mean age of the whole group was 51 ± 11
years, prevalence of diabetes was 14%, duration of PD was 43 ± 30
months, percentage of women was 45%, and percentage of patients using a cycler
was 33%. We observed no differences between groups with regard to those
variables or creatinine clearance, residual renal function, Ca, phosphorus,
parathormone, C-reactive protein, lipid parameters, and use of phosphate
binder with or without Ca content. Mean arterial pressure was higher in the
high-Ca group, but the difference was not statistically significant (100
± 22 mmHg vs 88 ± 18 mmHg, p = 0.06). At baseline, AI
was significantly higher in the high-Ca group than in the low-Ca group (27%
± 10% vs 21% ± 9%, p < 0.05). Measurements of PWV
were not different between the groups (8.4 ± 1.1 m/s vs 8.5 ±
1.7 m/s). Measurement of arterial stiffness parameters at month 6 revealed
that PWV had increased in the high-Ca group (to 9.6 ± 2.3 m/s from 8.4
± 1.1 m/s, p < 0.05), but had not changed in the low-Ca
group (to 8.2 ± 1.9 m/s from 8.5 ± 1.7 m/s). The AI did not
change in either group.
Conclusions: These data suggest that Ca exposure
through PD solution plays a role in the progression of arterial stiffness,
which may be related to increased vascular calcification.
KEY WORDS: Dialysate calcium; arterial stiffness.
Cardiovascular disease accounts for more than 50% of overall mortality in
dialysis patients (1). Arteries
in dialysis patients are much stiffer than in a general population of the same
age and blood pressure level
(2). The origin of arterial
stiffness in uremic patients is not fully known. But some causative factors
have been suggested: chronic fluid overload, arterial calcification,
microinflammation, sympathetic nervous system overactivity, activation of the
renin–angiotensin–aldosterone system, increased lipid oxidation,
and abnormalities of the nitric oxide system
(3).
Peritoneal dialysis (PD) patients seem to have a worse cardiovascular
profile than that found in hemodialysis patients. The reasons for poor outcome
are not apparent. Possibilities include less-successful blood pressure
control, worse lipid profile, and greater oxidative stress caused by PD
solutions (4). The importance
of PD fluid Ca to the progression of arterial stiffness in PD patients is not
known. In this prospective study, we investigated whether there is a
relationship between dialysate Ca content and arterial stiffness in PD
patients.
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PATIENTS AND METHODS
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Between September 2006 and January 2008, we enrolled into the study 49 PD
patients who had been treated with same PD solution for the preceding 6 months
at Ege University Dialysis Center. Of these patients, 33 were on continuous
ambulatory PD, and 16 were on automated PD. Patients were divided into 2
groups according to dialysate Ca content: 15 patients had been receiving a
solution with a Ca content of 1.75 mmol/L (high-Ca group), and the other 34
patients had been receiving a solution with a Ca content of 1.25 mmol/L
(low-Ca group). All patients were followed for 6 months on the same
prescription.
Arterial stiffness was assessed by measurement of the augmentation index
(AI) and brachial pulse wave velocity (PWV) at baseline and at month 6 of
follow-up (SphygmoCor: Atcor Medical, West Ryde, NSW, Australia). Demographic
data were recorded from patient charts. Biochemical measurements were
performed at the time of the PWV investigation. All patients underwent
echocardiographic examination and carotid artery intima media thickness
(CA-IMT) measurement by B-mode ultrasonography at the beginning of the study.
Left atrium diameter (LAd) was corrected for body surface area (BSA).
Cardiothoracic index (CTI) was measured on chest radiographs in all patients
at the time of investigation.
STATISTICAL ANALYSES
Data are expressed as mean ± standard deviation. Proportions were
compared by chi-square analysis. The Student t-test, analysis of
variance, and Mann–Whitney test were used for group comparisons. A
p value of less than 0.05 was considered significant.
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RESULTS
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Across the whole group of patients, mean age was 51 ± 11 years;
duration of PD, 43 ± 30 months; percentage of women, 45%; prevalence of
diabetes, 10%; and percentage of patients using cycler, 33%. For the whole
group at baseline, mean AI was 23% ± 10%, and mean PWV was 8.4 ±
1.6 m/s. Correlation analysis showed that AI was positively correlated with
systolic blood pressure (SBP), mean arterial pressure (MAP), LAd/BSA, and CTI.
Patients' PWV was positively correlated with age, SBP, diastolic blood
pressure, MAP, serum HbA1c, and CA-IMT.
When the high-Ca and low-Ca groups were compared, we observed no
statistical differences between them with respect to creatinine clearance,
residual renal function, serum Ca, serum phosphorus, serum parathormone, serum
C-reactive protein, lipid parameters, and use of phosphate binders with or
without Ca content. Although MAP was higher in the high-Ca group, the
difference was not statistically significant (100 ± 22 mmHg vs 88
± 18 mmHg, p = 0.06).
Mean AI was significantly higher in the high-Ca group than in the low-Ca
group at baseline (27% ± 10% vs 21% ± 9%, p < 0.05).
But mean PWV was not different between the groups at baseline (8.4 ±
1.1 m/s vs 8.5 ± 1.7 m/s). At month 6 of follow-up for arterial
stiffness in the 2 groups, PWV was observed to be increased in the high-Ca
group (to 9.6 ± 2.3 m/s from 8.4 ± 1.1 m/s, p <
0.05), but no change was observed in the low-Ca group (to 8.2 ± 1.9 m/s
from 8.5 ± 1.7 m/s). At month 6 of follow-up, the AI had not changed in
either group (Table 1).
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DISCUSSION
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In our study, we evaluated the effect of dialysate Ca content on arterial
stiffness in PD patients. Our results showed that dialysis with high dialysate
Ca (1.75 mmol/L) was associated with increased arterial stiffness at the end
of follow-up (as presented by increased PWV, which is a surrogate marker of
arterial stiffness with high-Ca solutions). The AI did not change during
follow-up. Measurement of PWV is a more sensitive method than AI for
evaluating arterial stiffness. We also found that PWV was positively
correlated with CA-IMT.
The foregoing findings demonstrate that increased arterial stiffness
accompanies increased atherosclerosis in PD patients. The literature contains
few studies concerning the effect of dialysate Ca content on arterial
stiffness. Kyriazis et al.
(5,6)
showed that, as compared with treatment with low dialysate Ca (1.25 mmol/L),
treatment with high dialysate Ca (1.75 mmol/L) induced a significant,
blood-pressure-independent increase in measured arterial stiffness parameters
in hemodialysis patients. By reducing the incidence of hemodialysis-induced
hypercalcemia, hemodialysis with low dialysate Ca may have a beneficial role
in minimizing the cardiovascular risk related to the intermittent
intradialytic increase in arterial stiffness inherent in the chronic use of
high dialysate Ca
(5,6).
To our concern, no study has investigated this topic in PD patients. Our study
is the first prospective investigation to report this association in PD
patients.
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CONCLUSIONS
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Our data suggest that Ca exposure in PD solution plays a role in the
progression of arterial stiffness, which may be related to increased vascular
calcification.
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ABSTRACT
PATIENTS AND METHODS
