Seasonal modifications in blood pressure are mainly related to interdialytic body weight gain in dialysis patients

Resistant hypertension in dialysis

Hypertension is the most common finding in chronic kidney disease patients, with prevalence ranging from 60% to 90% depending on the stage and etiology of the disease. It is also a significant independent risk factor for cardiovascular disease, progression to end-stage kidney disease and mortality. According to the current guidelines, resistant hypertension is defined in the general population as uncontrolled blood pressure on three or more antihypertensive drugs in adequate doses or when patients are on four or more antihypertensive drug categories irrespective of the blood pressure control, providing that antihypertensive treatment included diuretics. The currently established definitions of resistant hypertension are not directly applicable to the end-stage kidney disease setting. The diagnosis of true resistant hypertension requires confirmation of adherence to therapy and confirmation of uncontrolled blood pressure values by ambulatory blood pressure measurement or home blood pressure measurement. In addition, the term "apparent treatment-resistant hypertension," defined as an uncontrolled blood pressure on three or more antihypertensive medication classes, or use of four or more medications regardless of blood pressure level was introduced. In this comprehensive review we focused on the definitions of hypertension, and therapeutic targets in patients on renal replacement therapy, including the limitations and biases. We discussed the issue of pathophysiology and assessment of blood pressure in the dialyzed population, management of resistant hypertension as well as available data on prevalence of apparent treatment-resistant hypertension in end-stage kidney disease. To conclude, larger sample-size and even higher quality studies about drug adherence should be conducted in the population of patients with the end-stage kidney disease who are on dialysis. It also should be determined how and when blood pressure should be measured in the group of dialysis patients. Additionally, it should be stated what the target blood pressure values in this group of patients really are. The definition of resistant hypertension in this group should be revisited, and its relationship to both subclinical and clinical endpoints should be established.

An observational study on the effect of seasonal variation on peritoneal dialysis patients

Background: Seasonal variation has an impact on plants, wild animals, and also human beings. Data have shown seasonal variation has a significant impact on patients' fluid status, biochemistry results, and outcomes in hemodialysis populations. The relevant data on peritoneal dialysis is scant. Methods: This was a cross sectional study. All patients followed up in our center had a peritoneal equilibration test and PD adequacy test every 6 months. All the peritoneal equilibration test and PD adequacy test data were collected during December 2019 to November 2020. The monthly delivery information of the whole center was collected from 2015 to 2019. Results: There were 366 patients and 604 sets of peritoneal equilibration test and PD adequacy test results in the study. Plasma albumin and phosphate levels were higher in summer. The monthly average outdoor temperature was positively correlated with plasma albumin. There was no seasonal difference in peritoneal dialysis ultrafiltration or urine volume. The percentage of low glucose concentration (1.5%) usage was higher in summer and lower in winter. Conclusion: Plasma albumin and phosphate levels were higher in summer in PD patients. Weaker glucose peritoneal dialysis dialysate was more widely used in summer. Understanding the seasonal variation of peritoneal dialysis is helpful in individualized treatment.

Seasonal Variation: A Non-negligible Factor Associated With Blood Pressure in Patients Undergoing Hemodialysis

Objective

To investigate a seasonal variation in blood pressure (BP) for patients undergoing hemodialysis (HD).

Methods

In this retrospective study, we exported all BP measurements from the information system to investigate a seasonal variation of BP. We also investigated a seasonal variation in BP for patients of different gender types, of different age groups, with diabetic nephropathy (DN), and with non-DN having HD. Multiple linear regression models were used to explore the associations between BP and climatic parameters.

Results

In 2019, a total of 367 patients had received HD therapy in the Longwen HD unit. We included nearly 40,000 pre-dialysis BP measurements. The result of our study demonstrated a clear seasonal variation in pre-dialysis BP in general patients with HD, in male and female patients, and patients with DN and non-DN. December seemed to be a peak in the values of pre-dialysis systolic BP (SBP) and diastolic BP (DBP). The nadir values of pre-dialysis SBP and DBP were observed in June and July, respectively. A difference between peak and nadir values of BP is 3.81/2.20 mmHg in patients undergoing HD. Maximal seasonal variation in BP is 9.03/5.08 mmHg for patients with DN. A significant association of SBP and DBP with climatic parameters was found in this study. Pre-dialysis BP was inversely correlated with outdoor temperature, daytime length, and relative humidity.

Conclusion

A clear seasonal variation in BP is observed for patients with HD. Pre-dialysis SBP and DBP are inversely associated with outdoor temperature, daytime length, and relative humidity. The magnitude of a seasonal variation in BP increases in patients with DN.

Monthly trends and seasonality of hemodialysis treatment and outcomes of newly initiated patients from the national database (NDB) of Japan

BACKGROUND

The numbers of patients treated with hemodialysis (HD) in Japan are currently quantified by manual survey. As this method requires much effort from medical institutions and cannot achieve 100% response, a more practical method is required. We aimed to establish a novel method for determining the static and dynamic numbers of patients treated with HD.

METHODS

This observational study used the national medical billing database (termed NDB) of Japan, based on the records of the universal healthcare insurance system. Medical billing data registered in the NDB between April 2011 and March 2015 were analyzed. From 130 billion records, we extracted and analyzed records of patients who had undergone HD at least once per month. Patients' monthly condition was classified as newly initiated HD, chronic HD, or presumed death, using conditional expressions. We also investigated renal outcome and presumed survival in newly initiated HD patients.

RESULTS

In the last month of the study period, 274,100 patients were identified as receiving chronic HD, which is estimated as > 95% of the number of these patients identified in the manual survey so far. The monthly data showed clear seasonality in the incidence of transient HD, which increased in winter and decreased in summer.

CONCLUSION

Analysis of a large national database revealed a significant increase in transient HD in winter and decrease in summer. Applied to additional epidemiological exploratory studies or clinical research, this analytical technique would enable collection of the dynamics of almost all HD patients nationwide.

Seasonal variation and predictors of intradialytic blood pressure decline: a retrospective cohort study

The risk factors for intradialytic systolic blood pressure decline remain poorly understood. We aimed to identify clinical and laboratory predictors of the intradialytic systolic blood pressure decline, considering its seasonal variation. In a retrospective cohort of 47,219 hemodialysis sessions of 307 patients undergoing hemodialysis over one year in three dialysis clinics, the seasonal variation and the predictors of intradialytic systolic blood pressure decline (predialysis systolic blood pressure--nadir intradialytic systolic blood pressure) were assessed using cosinor analysis and linear mixed models adjusted for baseline or monthly hemodialysis-related variables, respectively. The intradialytic systolic blood pressure decline was greatest and least in the winter and summer, respectively, showing a clear seasonal pattern. In both models adjusted for baseline and monthly hemodialysis-related parameters, calcium channel blocker use was associated with a smaller decline (-4.58 [95% confidence interval (CI), -5.84 to -3.33], P < 0.001; -3.66 [95% CI, -5.69 to -1.64], P < 0.001) and α blocker use, with a greater decline (3.25 [95% CI, 1.53-4.97], P < 0.001; 3.57 [95% CI, 1.08-6.06], P = 0.005). Baseline and monthly serum phosphorus levels were positively correlated with the decline (1.55 [95% CI, 0.30-2.80], P = 0.02; 0.59 [95% CI, 0.16-1.00], P = 0.007), and baseline and monthly normalized protein catabolic rates were inversely correlated (respectively, -22.41 [95% CI, -33.53 to -11.28], P < 0.001; 9.65 [95% CI, 4.60-14.70], P < 0.001). In conclusion, calcium channel blocker use, α blocker avoidance, and serum phosphorus-lowering therapy may attenuate the intradialytic systolic blood pressure decline and should be investigated in prospective trials.

The effect of ambient temperature on blood pressure of patients undergoing hemodialysis in the Pantanal-Brazil

The objective was to analyze the association of changes in pre-dialysis systolic and diastolic blood pressure with air temperature in a municipality in the Brazilian Pantanal, a tropical climate area. Longitudinal panel study, with analysis of mixed effects models of 133 hemodialysis patients in the city of Cáceres-Mato Grosso in 2014. Air temperature showed an inverse association with pre-dialysis systolic and diastolic blood pressure. With each increase of 1 °C in the mean air temperature, the pre-dialysis systolic blood pressure decreases -0.730mmHg (p ≤ 0.000) and the pre-dialysis diastolic blood pressure decreases -0.280mmHg (p ≤ 0.000). The estimated effect was greater for systolic blood pressure, but both pre-dialysis blood pressure measures are reduced with an increase in lag (up to two days), even when adjusted for relative air humidity. Air temperature is determinant for changes in pre-dialysis systolic and diastolic blood pressure in hemodialysis patients. The temperature effect was greater for systolic blood pressure than for diastolic blood pressure.

Uncertainties in BP management in dialysis patients

Hypertension in dialysis patients is extremely common. In this article, we review the current evidence for blood pressure (BP) goals in hemodialysis patients, and consider the effectiveness of interventions by which BP may be lowered, including manipulation of dietary and dialysate sodium; optimization of extracellular water; prolongation of dialysis time; and antihypertensive medication. Although two meta-analyses suggest lowering BP using antihypertensive drugs might be beneficial in reducing cardiovascular events and mortality, there are insufficient rigorously designed trials in hypertensive hemodialysis populations to determine preferred antihypertensive drug classes. We suggest aiming for predialysis systolic BP between 130 and 159 mm Hg, while at the same time acknowledge the significant limitations of the data upon which it is based. We conclude by summarizing current knowledge as regards management of hypertension in the peritoneal dialysis population and make recommendations for future research in this field.

Geographical Variations in Blood Pressure Level and Seasonality in Hemodialysis Patients

Seasons and climate influence the regulation of blood pressure (BP) in the general population and in hemodialysis patients. It is unknown whether this phenomenon varies across the world. Our objective was to estimate BP seasonality in hemodialysis patients from different geographical locations. Patients from 7 European countries (Spain, Italy, France, Belgium, Germany, United Kingdom, and Sweden) participating in the DOPPS (Dialysis Outcomes and Practice Patterns Study) on years 2005 to 2011 were studied. Factors influencing pre- and postdialysis systolic BP and diastolic BP levels were analyzed by mixed models. There were 9655 patients (median age, 68; 59% male) from 263 facilities, seen every 4 months during a median duration of 1.3 years. Pre- and postdialysis systolic BP increased by a mean estimate of 5.1 mm Hg (95% confidence interval [CI], 3.7-6.4 mm Hg) and 4.4 mm Hg (95% CI, 2.9-5.9 mm Hg) for each 10° increase in latitude (1111 km to the North). In the longitudinal analysis, predialysis systolic BP was lower in summer and higher in winter (difference, 1.7 mm Hg; 95% CI, 1.3-2.2 mm Hg), with greater differences in southern locations (P_interaction=0.04). Predialysis systolic BP was inversely associated with outdoor temperature (-0.8 mm Hg/7.2°C; 95% CI, -1.0 to -0.5 mm Hg/7.2°C), with steeper slopes in southern locations (P_interaction=0.005). Results were similar for predialysis diastolic BP. In conclusion, there is a geographical and seasonal gradient of BP in European hemodialysis patients. There is a need to consider these effects when evaluating and treating BP in this population and potentially in others.

Seasonal variations in transition, mortality and kidney transplantation among patients with end-stage renal disease in the USA

Background

Seasonal variations may exist in transitioning to dialysis, kidney transplantation and related outcomes among end-stage renal disease (ESRD) patients. Elucidating these variations may have major clinical and healthcare policy implications for better resource allocation across seasons.

Methods

Using the United States Renal Data System database from 1 January 2000 to 31 December 2013, we calculated monthly counts of transitioning to dialysis or first transplantation and deaths. Crude monthly transition fraction was defined as the number of new ESRD patients divided by all ESRD patients on the first day of each month. Similar fractions were calculated for all-cause and cause-specific mortality and transplantation.

Results

The increasing trend of the annual transition to ESRD plateaued during 2009-2012 (n = 126 264), and dropped drastically in 2013 (n = 117 372). Independent of secular trends, monthly transition to ESRD was lowest in July (1.65%) and highest in January (1.97%) of each year. All-cause, cardiovascular and infectious mortalities were lowest in July or August (1.32, 0.58 and 0.15%, respectively) and highest in January (1.56, 0.71 and 0.19%, respectively). Kidney transplantation was highest in June (0.33%), and this peak was mainly attributed to living kidney transplantation in summer months. Transplant failure showed a similar seasonal variation to naïve transition, peaking in January (0.65%) and nadiring in September (0.56%).

Conclusions

Transitioning to ESRD and adverse events among ESRD people were more frequent in winter and less frequent in summer, whereas kidney transplantation showed the reverse trend. The potential causes and implications of these consistent seasonal variations warrant more investigation.

Early changes in body weight and blood pressure are associated with mortality in incident dialysis patients

BACKGROUND

While much research is devoted to identifying novel biomarkers, addressing the prognostic value of routinely measured clinical parameters is of great interest. We studied early blood pressure (BP) and body weight (BW) trajectories in incident haemodialysis patients and their association with all-cause mortality.

METHODS

In a cohort of 357 incident patients, we obtained all records of BP and BW during the first 90 days on dialysis (over 12 800 observations) and analysed trajectories using penalized B-splines and mixed linear regression models. Baseline comorbidities and all-cause mortality (median follow-up: 2.2 years) were obtained from the French Renal Epidemiology and Information Network (REIN) registry, and the association with mortality was assessed by Cox models adjusting for baseline comorbidities.

RESULTS

During the initial 90 days on dialysis, there were non-linear decreases in BP and BW, with milder slopes after 15 days [systolic BP (SBP)] or 30 days [diastolic BP (DBP) and BW]. SBP or DBP levels at dialysis initiation and changes in BW occurring in the first month or during the following 2 months were significantly associated with survival. In multivariate models adjusting for baseline comorbidities and prescriptions, higher SBP value and BW slopes were independently associated with a lower risk of mortality. Hazard ratios of mortality and 95% confidence intervals were 0.92 (0.85-0.99) for a 10 mmHg higher SBP and 0.76 (0.66-0.88) for a 1 kg/month higher BW change on Days 30-90.

CONCLUSIONS

BW loss in the first weeks on dialysis is a strong and independent predictor of mortality. Low BP is also associated with mortality and is probably the consequence of underlying cardiovascular diseases. These early markers appear to be valuable prognostic factors.

Impact of use of angiotensin II receptor blocker on all-cause mortality in hemodialysis patients: prospective cohort study using a propensity-score analysis

BACKGROUND

It is controversial whether treatment with an angiotensin II receptor blocker (ARB) or a calcium channel blocker (CCB) improves prognosis of hemodialysis (HD) patients.

METHODS

This study was designed as a multicenter prospective cohort study. HD patients (n = 1071) were enrolled from 22 institutes in January 2009 and followed up for 3 years. Patients with missing data, kidney transplantation or retraction of consent during the follow-up period (n = 204) were excluded, and 867 patients contributed to analysis of mortality. Propensity score (PS) for use of ARB and that for CCB was calculated using a multiple logistic regression model.

RESULTS

ARB and CCB were prescribed in 45.6 and 54.7 % of patients at enrollment. During the 3-year follow-up period, all-cause mortality and cardiovascular mortality rates were 18.8 and 5.1 %, respectively. Kaplan-Meier curves showed that all-cause and cardiovascular mortality rates were lower in the ARB group than in the non-ARB group, though the mortality rates were similar in the CCB group and non-CCB group. In PS-stratified Cox regression analysis, ARB treatment was associated with 34 and 45 % reduction of all-cause death and cardiovascular death, respectively. In PS matching analysis, ARB treatment was associated with a significant reduction (46 % reduction) in the risk of all-cause death. A significant impact of CCB treatment on all-cause or cardiovascular mortality was not detected in PS analysis.

CONCLUSIONS

The use of an ARB, but not a CCB, is associated with reduced all-cause and cardiovascular mortalities in patients on HD.

Assessment of fluid and nutritional status using multifrequency bioelectrical impedance analysis in peritoneal dialysis patients

BACKGROUND/AIMS

The purpose of this study was to evaluate the clinical usefulness and relevance of bioelectrical impedance analysis (BIA) for assessing the fluid and nutritional status in peritoneal dialysis (PD) patients.

METHODS

Statistical analyses between various measures of fluid and nutritional status were performed in 106 cases of 64 patients.

RESULTS

Extracellular fluid/total body water (ECF/TBW) was correlated with systolic blood pressure, extremity edema, and antihypertensive medications (p = 0.042, p < 0.001, and p = 0.029, respectively). Body cell mass (BCM)/height(2) was correlated with SGA rating and PCR (p < 0.001 and p = 0.002, respectively). ECF/TBW and BCM/height(2) significantly predicted extremity edema (p < 0.001) and SGA rating (p = 0.001), respectively. ROC analysis yielded an ECF/TBW cut-off of 0.36 and a BCM/height(2) cut-off of 11.23. When the BCM/height(2) cut-off of 11.23 was applied to subclinical patients (SGA score ≥6), a significant difference in SGA rating was detected in subgroups (p = 0.010).

CONCLUSION

BIA yields useful and relevant information about hydration and nutritional status in PD patients.

Influence of seasonal variation on blood pressure measurements in children, adolescents and young adults

BACKGROUND

Seasonal fluctuations in outdoor temperature have been shown to affect blood pressure in adults. The aim of our study was to determine whether blood pressure measurements in children and adolescents in Central Europe undergo seasonal variation or are influenced by outdoor temperature.

METHODS

The blood pressure of 6,714 subjects (3,497 boys, 3,237 girls) aged 3 to 21 (median age 10.6) years was routinely measured. The study cohort comprised both healthy and sick children and adolescents visiting outpatient clinics and during hospitalisation.

RESULTS

Cross-sectional analysis showed a significant seasonal variation in blood pressure measurements. The mean increase of systolic/diastolic blood pressure was 4.45/2.42 mmHg during the winter. A significant correlation between average outdoor temperature and systolic blood pressure was found (ρ = -0.074 p < 0.001). However, the effect was only detectable at an average temperature below 0 °C/32 °F and above 10 °C/50 °F. For each 1 °C increase in average outdoor temperature, the systolic blood pressure fell by 0.12 mmHg.

CONCLUSIONS

Blood pressure measurements in children and adolescents, even in a temperate climate, are influenced by temperature and subject to seasonal variation. Considering seasonal variations in blood pressure could be of clinical interest.

Home blood pressure control after the great East Japan earthquake in patients on chronic hemodialysis

At 14:46 on 11 March 2011, northeastern Japan was struck by a major earthquake measuring 9.0 on the Richter scale (the Great East Japan Earthquake). Several reports have suggested a transient blood pressure (BP) increase after a major earthquake, but its impact on BP in chronic dialysis patients has not been reported. In a retrospective review of 25 hemodialysis patients who were residents of Koriyama City, changes in the morning home BP after the earthquake were investigated. Home systolic and diastolic BPs were significantly elevated 1 week after the earthquake (158 ± 16 mm Hg vs. 151 ± 13 mm Hg, P < 0.01, for systolic; 81 ± 13 mm Hg vs. 78 ± 11 mm Hg, P = 0.01, for diastolic). Mean home BP 1 week after the earthquake was unchanged from baseline in patients treated with sympatholytics and/or renin-angiotensin system (RAS) inhibitors. BP values returned to baseline by 4 weeks after the earthquake, but percent changes in mean BP were significantly greater even 2 weeks, 4 weeks, and 6 weeks after the earthquake in patients not treated with RAS inhibitors than in those treated with RAS inhibitors (2 weeks 7.0% ± 4.5% vs. 0.2% ± 5.0%, P < 0.01; 4 weeks 4.4% ± 5.9% vs. -1.8% ± 5.3%, P = 0.02; 6 weeks 4.6% ± 4.9% vs. -1.9% ± 3.9%, P < 0.01). On multiple regression analysis, RAS inhibitor use had an independent relationship with percentage increases in mean BP during the 6 weeks after the earthquake. Home BP was significantly increased after a major earthquake in patients on chronic hemodialysis. Prolonged deterioration of BP control after the earthquake was associated with non-use of RAS inhibitors.

Identification of impeding factors for dry weight achievement in end-stage renal disease after appropriate kidney graft function

The aim of this study was to evaluate the factors that prevent dry weight achievement in patients with end-stage renal disease (ESRD) in renal replacement therapy through the change in their body weight after kidney transplant (KT) compared with 1 week before KT. The study included 188 ESRD patients of diverse etiology who received living kidney transplantation with normal immediate graft function, 62.2% were male, age 29 ± 11 years old. All patients were on renal replacement therapy for at least 1 month before KT with either hemodiafiltration (N = 106), hemodialysis (N = 25), or peritoneal dialysis (N = 57). Based on body weight difference (after transplant-before transplant), patients with body weight difference ≤2 kg were considered as being close to their dry weight (Group 1, N = 112), whereas patients with body weight difference >2 kg were considered as being overhydrated (Group 2, N = 76). Clinical and biochemical characteristics were obtained from the medical records at three periods of time: time of ESRD initiation (baseline), 1 week before undergoing KT, and 1 week after KT. The mean time (± standard deviation) from renal replacement therapy initiation to the week before KT was 9.2 ± 5 months. Group 2 had a higher proportion of men, antihypertensive use, peritoneal dialysis, and higher urine output during all periods. Before KT, Group 2 had higher systolic and diastolic blood pressures than Group 1. After KT, both systolic and diastolic blood pressures decreased in Group 2, whereas no change occurred in Group 1. Before KT, Group 2 had higher levels of blood urea nitrogen, creatinine, uric acid, and phosphorous compared with Group 1. Compared with baseline, Group 1 had more optimal blood urea nitrogen, creatinine, and uric acid parameters before KT than Group 2. After KT, all parameters improved with respect to baseline in both groups. Hemoglobin, albumin, and sodium were similar between groups, except for higher hemoglobin in Group 2 than Group 1 after KT. Multivariate regression analysis showed that male sex, peritoneal dialysis, and systolic blood pressure before KT were independent risk factors for overhydration. In conclusion, high systolic blood pressure and peritoneal dialysis were two independent modifiable variables associated with overhydration before KT. Assessment of the body weight change after KT is a useful tool to evaluate dry weight, in addition to identifying variables associated with poor volume control. This could allow adjustment of clinical and dialysis parameters in future patients.

Seasonal variations in mortality, clinical, and laboratory parameters in hemodialysis patients: a 5-year cohort study

BACKGROUND AND OBJECTIVES

Mortality varies seasonally in the general population, but it is unknown whether this phenomenon is also present in hemodialysis patients with known higher background mortality and emphasis on cardiovascular causes of death. This study aimed to assess seasonal variations in mortality, in relation to clinical and laboratory variables in a large cohort of chronic hemodialysis patients over a 5-year period.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study included 15,056 patients of 51 Renal Research Institute clinics from six states of varying climates in the United States. Seasonal differences were assessed by chi-squared tests and univariate and multivariate cosinor analyses.

RESULTS

Mortality, both all-cause and cardiovascular, was significantly higher during winter compared with other seasons (14.2 deaths per 100 patient-years in winter, 13.1 in spring, 12.3 in autumn, and 11.9 in summer). The increase in mortality in winter was more pronounced in younger patients, as well as in whites and in men. Seasonal variations were similar across climatologically different regions. Seasonal variations were also observed in neutrophil/lymphocyte ratio and serum calcium, potassium, and platelet values. Differences in mortality disappeared when adjusted for seasonally variable clinical parameters.

CONCLUSIONS

In a large cohort of dialysis patients, significant seasonal variations in overall and cardiovascular mortality were observed, which were consistent over different climatic regions. Other physiologic and laboratory parameters were also seasonally different. Results showed that mortality differences were related to seasonality of physiologic and laboratory parameters. Seasonal variations should be taken into account when designing and interpreting longitudinal studies in dialysis patients.

High Water Evaporation Rate is Associated with Low Blood Pressure in Chronic Peritoneal Dialysis Patients

Background

The relationship between water evaporation rate (WER) and blood pressure (BP) in continuous ambulatory peritoneal dialysis (CAPD) patients has not been addressed before. This study was undertaken to evaluate the effects of WER on the BP and body weight (BW) of end-stage renal disease patients treated with CAPD.

Methods

Based on mean WER of each month, the year 2005 was divided into “high WER” and “low WER” stages. This study enrolled 66 CAPD patients at our center during 2005. The BP and BW of each patient were collected monthly. WER was measured with a class A evaporation pan.

Results

Compared to the high WER stage, CAPD patients had higher BP (systolic: 142 ± 29 vs 134 ± 27 mmHg, p < 0.001; diastolic: 86 ± 17 vs 84 ± 16 mmHg, p < 0.001) and BW (56.8 ± 10.2 vs 56.1 ± 10.2 kg, p < 0.001) in the low WER stage. Ambient temperature was significantly higher in the high WER stage ( p = 0.004) and it was also positively correlated with WER ( r = 0.82, p = 0.0012). Both mean BP ( r = –0.72, p = 0.0089) and BW ( r = –0.79, p = 0.002) showed inverse relationships to the WER. Moreover, both mean BP ( r = –0.95, p < 0.001) and BW ( r = –0.90, p < 0.001) also showed negative linear regressions to ambient temperature. There was a positive linear regression between mean BP and BW ( r = 0.85, p = 0.0004). Multiple linear regression analysis found that WER (β = –0.672, p = 0.026) was an independent factor correlated to patients’ mean BP.

Conclusions

CAPD patients had lower BP and BW in the high WER stage. These decreases were associated with higher ambient temperature and WER. We hypothesize that increased insensible salt and fluid loss secondary to high WER during hot seasons, especially in subtropical areas, ameliorates the hypervolemia and hypertension in CAPD patients.

The Effect of Weather on Peritoneal Dialysis (PD) Prescription: Seasonal Variation in PD Dialysate Utilization

♦ Background

There have been no reports on peritoneal dialysis (PD) solution utilization since this treatment was developed in the 1920s. The aim of the present investigation was to investigate if weather affects PD prescription.

♦ Study Design and Methods

This 10-year observational study used the Taiwan National Health Insurance Research Database. Setting and Participants: Claims for different concentrate PD dialysate were analyzed monthly. 2.5% and 4.25% PD solutes were defined as hypertonic solutions. Predictor: Monthly outdoor mean temperature. Outcome and Measurement: The relationship between monthly mean of PD dialysate utilization and monthly outdoor temperature was analyzed by linear regression. Monthly mean PD dialysate utilization amount in 4 quarters was analyzed by ANOVA.

♦ Results

During the 10-year study period, a clear seasonal variation in PD dialysate was observed. This seasonal variation was present regardless of age, gender, and the presence of hypertension, diabetes, and dyslipidemia. Monthly mean temperature was positively correlated to 1.5% dialysate utilization amount ( r = 0.559, p < 0.001) and negatively correlated to 2.5% ( r = –0.533, p < 0.001) and 4.25% ( r= –0.410, p < 0.001) dialysate utilization amount. In longitudinal follow-up, hypertonic PD fluid utilization was higher in diabetic patients than in nondiabetic patients from the beginning of treatment. Thereafter, it increased rapidly and reached a plateau within 1 year. Limitations: Analysis of ultrafiltration amount, blood pressure, and body weight was unfeasible due to the nature of the database.

♦ Conclusions

The utilization of differential strengths of PD solutions has a seasonal cyclic pattern, with more hypertonic PD solution utilized in winter and more hypotonic PD solution in summer.

Arterial stiffness is related to augmented seasonal variation of blood pressure in hypertensive patients

BACKGROUND

Seasonal variation in blood pressure (BP), a usual tendency of both systolic (SBP) and diastolic BP (DBP) to rise during winter in hypertensive patients, may be related to the higher cardiovascular mortality in winter. However, it is not yet clear what factors are relevant to the seasonal BP changes. We hypothesized that arterial stiffness is related to the BP changes between summer and winter.

METHODS AND RESULTS

Eighty-five elderly (>55 years) patients with essential hypertension (33 males, 64+/-6.0 years) were enrolled. Seasonal BP profiles over at least 2 years were studied along with arterial stiffness and clinical variables (age, gender, smoking, duration of hypertension, anti-hypertensive medications and body mass index). Both SBP and DBP were significantly higher during winter compared with three other seasons (spring 128+/-10.0/79+/-7.3 mmHg, summer 127+/-9.8/78+/-7.1 mmHg, autumn 127+/-10.3/78+/-8.0 mmHg, winter 136+/-12.5/81+/-7.6 mmHg; SBP changes; p<0.001, DBP changes; p<0.001). There were no significant seasonal differences among spring, summer and autumn. Pulse wave velocity (PWV), a widely used clinical indicator of arterial stiffness was correlated with winter-summer differences in SBP (r = 0.272, p = 0.012), but not in DBP (r = 0.188, p = 0.085). Age, which was correlated with PWV strongly (p<0.001), was not significantly related to the seasonal changes in BP (SBP changes; p = 0.114, DBP changes; p = 0.298). No other clinical variables had significant correlation with seasonal BP changes. Multivariate regression analysis revealed that PWV is the only significant predictor for winter-summer SBP changes.

CONCLUSIONS

Our results established a feasible link between arterial stiffness and seasonal BP variation. These findings may partly explain higher cardiovascular risk in patients with increased arterial stiffness.

Seasonal Variation in Blood Pressure of Patients on Continuous Ambulatory Peritoneal Dialysis

BACKGROUND

A seasonal variation in blood pressure (BP) has been observed in hemodialysis and renal transplant patients. However, this phenomenon in continuous ambulatory peritoneal dialysis (CAPD) patients, whose hemodynamics are different from hemodialysis patients, has not been reported before. In addition, the contribution of extracellular water (ECW) in the seasonal variation in BP is not clear.

METHODS

All stable CAPD patients (n = 122) dialyzed in a single center from January 1, 2003 to December 12, 2004 were studied. Systolic blood pressure (SBP), diastolic blood pressure (DBP), weight and ECW (by bioimpedance analysis) were measured in every patient. Climatic data were obtained from the Beijing Weather Bureau. These data were pooled together and grouped according to the calendar month.

RESULTS

In general, an apparent seasonal variation in BP was observed in CAPD patients. BP began to decrease from spring and reached the lowest level in summer, then increased from autumn and reached its peak in winter. The seasonal variation in BP in male patients was similar to that in female patients, but in comparison to non-diabetic patients there was no apparent seasonal variation in the BP of diabetic patients. SBP and DBP negatively correlated with the average atmospheric temperature (r = -0.768, p < 0.001 and r = -0.764, p < 0.001, respectively). BP also negatively correlated with rainfall and humidity, but this correlation disappeared when temperature was controlled in partial correlation analysis. Weight and ECW fluctuated throughout the year but showed no seasonal variation.

CONCLUSION

On the whole there was an apparent seasonal variation in blood pressure in CAPD patients. As opposed to non-diabetic patients, there was no apparent seasonal variation in BP in diabetic patients. The seasonal variation in BP was influenced more by temperature than rainfall and humidity, and the change in ECW was not seasonal, suggesting that other mechanisms such as total peripheral resistance might play a more important role in this phenomenon.

Fellows' Forum in Dialysis: Interdialytic Weight Gain: Implications in Hemodialysis Patients

Interdialytic weight gain (IDWG) is an easily measurable parameter in the dialysis unit, routinely assessed at the beginning of the dialysis session. It is used along with clinical symptoms and signs and predialysis blood pressure readings to make decisions regarding the amount of fluid removal during a dialysis session. IDWG is also used as a basis for fluid and salt intake recommendations. However, advising fluid and salt restriction based solely on IDWG may not be appropriate because of its status as a nutritional indicator, as well. Very few studies have been designed to determine the direct effect of IDWG on morbidity and mortality. Any such effect is confounded by residual renal function and various comorbidities, the effects of which might be difficult to separate from those of IDWG. Most attempts to control IDWG have concentrated on requiring patients to reduce fluid and dietary salt intake. Although there does not seem to be a consensus at this point, it is likely that within the lower values of IDWG (less than 5.7% of dry weight), tighter control of fluid and salt intake might not be warranted since these values may reflect higher protein and calorie intake, indicating better nutritional status.

[Hyperkalemia in hypertensive patients undergoing regular hemodialysis during enalapril and fosinopril therapy]

INTRODUCTION

Hypertension is evident in 80%-85% of patients with chronic renal failure and antihypertensive therapy is needed in 25%-30% of patients. Apart from antihypertensive effect, ACEi's decrease the left ventricular hypertrophy and mortality in dialysis patients. Even so, their use is limited due to hyperkalemia.

OBJECTIVE

The objective of the study was to compare the effect of fosinopril and enalapril on serum potassium level in hypertensive hemodialysis patients.

METHOD

Prospective pilot study included 16 patients undergoing chronic hemodialysis, with mean age of 58.9 +/- 9.6 years and mean duration of hypertension 11.3 +/- 7.1 years. The effect of antihypertensive drugs of equivalent dose was followed during three periods (three months each): period 1 (therapy with enalapril), period 2 (therapy with fosinopril) and period 3 (therapy with enalapril). Dialysis conditions were constant and patients were without signs of catabolic state. Laboratory results were followed on monthly basis and mean values were compared by ANOVA-one way test. Difference between variables between periods was tested using Bonferoni method.

RESULTS

There was significant difference between mean serum potassium levels throughout three therapeutic periods (5.88 +/- 0.38 vs. 4.9910.44 vs. 5.46 +/- 0.46mmol/l; p<0.001). Difference was evident even in the first month of fosinopril therapy. The effect can not be explained by dialysis adequacy since Kt/ V was similar throughout three treatment periods (1.18 +/- 0.24 vs. 1.25 +/- 0.21 vs. 1.25 +/- 0.14; p=ns). Systolic blood pressure was regulated even better with fosinopril than with enalapril (187.5 +/- 21.4 mmHg vs. 160.0 +/- 20.0 mmHg; p=0.01) and this effect was prolonged during period 3 (160.0 +/- 26.1mmHg). Hemoglobin values mainly depended on specific anemia therapy and not on particular ACEi drug.

CONCLUSION

Fosinopril carries less risk of hyperkalemia in hypertensive hemodialysis patients than enalapril. Although definite conclusion may be drawn after well-designed studies, the results presented in this pilot study suggest that fosinopril may be recommended for hypertensive hemodialysis patients who are at risk to develop inter-dialytic hyperkalemia.