The circadian blood pressure rhythm in non-diabetic hemodialysis patients

Time of hemodialysis and risk of intradialytic hypotension and intradialytic hypertension in maintenance hemodialysis

Intradialytic hypotension and intradialytic hypertension are complications of hemodialysis (HD) associated with a higher risk of cardiovascular disease (CVD) and death. Blood pressure (BP) normally fluctuates in a circadian pattern, but whether the risk of intradialytic hypotension and intradialytic hypertension varies according to the time of the HD session is unknown. We analyzed two cohorts of thrice-weekly maintenance HD (N = 1838 patients/n = 64,503 sessions from the Hemodialysis [HEMO] Study, and N = 3302 patients/n = 33,590 sessions from Satellite Healthcare). Random effects logistic regression models examined the association of HD start time (at or before 9:00 a.m. [early AM], between 9:01 a.m. and 12:00 p.m. [late AM], and at or after 12:01 p.m. [PM]) with intradialytic hypotension (defined as nadir intra-HD systolic BP (SBP) < 90 mmHg if pre-HD SBP < 160 mmHg, or <100 mmHg if pre-HD SBP ≥ 160 mmHg) and intradialytic hypertension (SBP increase ≥ 10 mmHg from pre-HD to post-HD). Compared to early AM, late AM and PM were associated with an 8% (aOR 0.92, 95% CI 0.83-1.02) and a 16% (aOR 0.84, 95% CI 0.75-0.95) lower risk of intradialytic hypotension in HEMO, respectively. Conversely, compared to early AM, a monotonic higher risk of intradialytic hypertension was observed for late AM (aOR 1.23, 95% CI 1.12-1.35) and PM (aOR 1.41, 95% CI 1.27-1.56) in HEMO. These findings were consistent in Satellite. In two large cohorts of maintenance HD, we observed a monotonic lower risk of intradialytic hypotension and a monotonic higher risk of intradialytic hypertension with later dialysis start times. Whether HD treatment allocation to certain times of the day in hypotensive-prone or hypertensive-prone patients improves outcomes deserves further investigation.

Reproducibility of ambulatory blood pressure values and circadian blood pressure patterns in untreated subjects in a 1-11 month interval

OBJECTIVE

To evaluate in untreated subjects the reproducibility of mean values and four circadian patterns between two ambulatory blood pressure monitoring (ABPM) recordings separated by 1-11 months.

METHODS

We performed a retrospective analysis of 481 individuals (59% women) evaluated by ABPM on two occasions, visit 1 (V1) and 2 (V2), separated by 5.5+0.2 months. Four circadian patterns were defined by night/day systolic blood pressure (SBP) ratios: reverse dippers (RD), ratio >1.0; non-dippers (ND), ratio 0.9-1.0; dippers (D), ratio 0.8-<0.9; and extreme dippers (ED), ratio <0.8. Coefficients of correlation and concordance between the ABPM values at V1 and V2 and the reproducibility of the RD, ND, D and ED patterns were calculated by the percentage of the same profile from V1 to V2.

RESULTS

Mean 24-h blood pressure (BP) at V1 and V2 was 126.8/75.9±0.5/0.5 vs. 126.5/75.7±0.5/0.4 mmHg (NS). Nighttime SBP fall was 9.8±0.4 (V1) and 9.6±0.3% (V2) (NS). The correlation coefficient of ABPM data at V1 vs. at V2 was 0.41-0.69 (p<0.001) and the concordance coefficient was 0.34-0.57 (p<0.01). At V1, 38 subjects were classified as ED (7.9%); D, n=216 (44.9%), 187 as ND (38.9%) and 40 as RD (8.3%). At V2 only 26.3% of ED, 44.9% of D, 54.5% of ND and 40% of RD maintained the same profile as at V1.

CONCLUSION

In untreated subjects ABPM has high reproducibility for mean values but only modest reproducibility for circadian profiles, thereby challenging the prognostic value of BP dipping patterns.

Prognostic Significance of Regional Arterial Stiffness for Stroke in Hypertension

BACKGROUND

Hypertension is strongly associated with cardiovascular disease. It has been reported that arterial stiffness is related to cardiovascular mortality and morbidity in hypertensive patients and that the physiological evaluation of arterial stiffness may assist clinicians in the early detection of atherosclerosis.

SUMMARY

It has been demonstrated that increased arterial stiffness is an independent predictor of cardiovascular disease, including stroke. Arterial stiffness is associated with structural changes in the brain. However, the stiffness responses of muscular arteries are different from those of elastic arteries, and so the impact of arterial stiffness and the conclusions to be drawn may be different depending on the region in which the measurement is taken.

KEY MESSAGES

In this review, we summarize the current literature describing the association between arterial stiffness, including carotid-femoral and brachial-ankle pulse wave velocity and cardio-ankle vascular index, and cardiovascular disease, specifically stroke. We discuss the utility and prognostic significance of regional arterial stiffness measurements.

Effects of nutritional parameters on nocturnal blood pressure in patients undergoing hemodialysis

BACKGROUND

Malnutrition is a common problem in uremic patients. It is unclear whether there is an association between the degree of malnutrition and 24-h ambulatory blood pressure patterns in patients undergoing hemodialysis. In the present study, we observed the relationship between the degree of malnutrition and deterioration of the rhythm of diurnal blood pressure, which are both risk factors for cardiovascular morbidity-mortality and associated with hypervolemia.

METHOD

We observed 148 patients undergoing hemodialysis in the Nephrology Department of Celal Bayar University Hospital. All cases were assessed for body weight alterations, dietary food intake, gastrointestinal symptoms, loss of subcutaneous fat and muscle tissue, presence and severity of comorbidities, functional capacity (subjective global assessment), and anthropometric indices. Ambulatory blood pressure measurements were performed for all cases on the day between the two hemodialysis sessions.

RESULTS

We found that the circadian blood pressure rhythm deteriorated in patients with a high-malnutrition score, and that malnutrition was more common and severe in those subjects with the non-dipper and reverse-dipper blood pressure patterns. Malnutrition score was positively correlated with the nighttime systolic and nighttime mean blood pressures and mean 24-h arterial blood pressure (all p ≤ 0.01). We identified a positive correlation between malnutrition score and the reduction in serum albumin and anthropometric indices.

CONCLUSION

This is the first study to demonstrate an association between malnutrition and deterioration in the circadian blood pressure rhythm in a hemodialysis population. Nutritional disturbance is associated with an increase in night-time blood pressure. Low serum albumin levels and hypervolemia may contribute this situation.

Blood pressure variability, cardiovascular risk, and risk for renal disease progression

The adverse cardiovascular consequences of high blood pressure (BP) not only depend on absolute BP values, but also on BP variability (BPV). Evidence has been provided that independently of mean BP levels, BP variations in the short- and long-term are associated with the development, progression and severity of cardiac, vascular and renal organ damage, and with an increased risk of CV events and mortality. Alterations in BPV have also been shown to be predictive of the development and progression of renal damage, which is of relevance if considering that impaired renal function in a hypertensive patient constitutes a very potent predictor of future CV events and mortality even in treated subjects. This review will address whether antihypertensive treatment should target alterations in BPV, in addition to reducing absolute BP levels, in order to achieve the highest CV and renal protection in hypertensive and renal patients.

Challenges in blood pressure measurement in patients treated with maintenance hemodialysis

The association between blood pressure and cardiovascular outcomes in patients undergoing hemodialysis remains controversial. This may relate in part to the technique and device used and the timing of the blood pressure measurement in relation to the hemodialysis procedure. Emerging evidence indicates that standardized hemodialysis unit blood pressure measurements or measurements obtained at home, either by the patient or using an ambulatory blood pressure monitor, may offer advantages over routine hemodialysis unit blood pressure measurements for determining cardiovascular risk and treatment. This review discusses the available evidence and implications for clinicians and clinical trials.

Pre- and postdialysis blood pressures are imprecise estimates of interdialytic ambulatory blood pressure

BP readings that are obtained in the dialysis unit are commonly used to make therapeutic decisions by clinicians and to predict morbidity and mortality by epidemiologists. Dialysis unit BP are also incorporated in the recent guidelines to target BP control. The magnitude of the difference, overestimation or underestimation, and agreement between dialysis unit BP and ambulatory BP (ABP) are unknown. Articles were selected from Medline to identify those that reported both ABP and dialysis unit BP in hemodialysis patients. Bias was calculated as the difference between dialysis unit and the corresponding ABP. Agreement limits between the BP measurement techniques were assessed by pooled SD of the difference using Bland-Altman methods. Predialysis systolic BP generally overestimated ABP by a variable amount. The heterogeneity between BP measurements did not allow for pooling of the estimates. The agreement limits between the two BP was 41.7 to -25.2 mmHg. Predialysis diastolic BP also generally overestimated the ABP with wide agreement limits (23.7 to -18.9 mmHg). In contrast, postdialysis BP underestimated average ABP with wide agreement limits for both postdialysis systolic BP (33.1 to -36.3 mmHg) and diastolic BP (19.3 to -23.9 mmHg). Dialysis unit BP measurements are imprecise estimates of ABP. Better methods are needed for the assessment of BP in hemodialysis patients for clinical decision making.

The role of ambulatory blood pressure monitoring in chronic and end-stage renal disease

In the past 30 years or so, the introduction of 24-h ambulatory blood pressure monitoring (ABPM) has enabled a more comprehensive estimate of a patient's true blood pressure (BP) and its changes. Although this tool has been used in the general population for the diagnosis of white coat hypertension, its role in the clinical management of patients with chronic and end-stage kidney disease is less well defined. In patients with kidney disease, routine clinic and dialysis center BP measurements may be poor indicators of BP control. Loss of the normal nocturnal decline in BP is also common. Moreover, there is increasing evidence that this loss, which ABPM alone can detect, is associated with poor renal and cardiovascular outcomes. To slow the progression of renal disease and lessen cardiovascular morbidity and mortality in patients with kidney disease, tight BP control is needed. However, the traditional methods of measuring BP intermittently in the medical setting may fail to provide an accurate picture of BP load. Ambulatory or some form of home BP monitoring should be more widely adopted in patients with chronic and end-stage renal disease.

Ambulatory blood pressure monitoring in hemodialysis patients: a critique and literature review

Ambulatory blood pressure (ABP) monitoring has been in use for nearly four decades. In that time, the advantages of using a more reproducible and accurate method to assess the true contribution of blood pressure to the cardiovascular risk profile of patients have steadily become more clearly established, balanced by the additional expense and expertise involved. In nephrology, and in particular in dialysis patients, there are significant difficulties in accurately registering truly representative blood pressure values and understanding the relationship between blood pressure, end-organ damage, and patient mortality. This arises because of the way in which hemodialysis acutely changes blood pressure values as well as the widespread abnormality of diurnal blood pressure rhythm seen in dialysis patients. Use of ABP monitoring can go some way to overcoming these obstacles. In this review we critically examine the use of ABP monitoring in the understanding of blood pressure control in dialysis patients.

Disasters and the heart: a review of the effects of earthquake-induced stress on cardiovascular disease

There is growing evidence that stress contributes to cardiovascular disease. Chronic stress contributes to the atherosclerotic process through increased allostatic load, which is mediated by the neuroendocrine and immune systems (sympathetic nervous system and hypothalamus-pituitary adrenal axis) and related chronic risk factors (insulin resistance syndrome, hypertension, diabetes, and hyperlipidemia). In addition, acute stress can trigger cardiovascular events predominantly through sympathetic nervous activation and potentiation of acute risk factors (blood pressure increase, endothelial cell dysfunction, increased blood viscosity, and platelet and hemostatic activation). Earthquakes provide a good example of naturally occurring acute and chronic stress, and in this review we focus mainly on the effects of the Hanshin-Awaji earthquake on the cardiovascular system. The Hanshin-Awaji earthquake resulted in a 3-fold increase of myocardial infarctions in people living close to the epicenter, particularly in women, with most of the increase occurring in nighttime-onset events. There was also a near doubling in the frequency of strokes. These effects may be mediated by changes in hemostatic factors, as demonstrated by an increase of D-dimer, von Willebrand factor, and tissue-type plasminogen activator (tPA) antigen. Blood pressure also increased after the earthquake, and was prolonged for several weeks in patients with microalbuminuria.

Ambulatory blood pressure measurement in the renal patient

Ambulatory blood pressure monitoring has been steadily growing in popularity as equipment becomes more accurate, affordable, and patient-friendly. In addition, software packages are more powerful and physician-customizable, and more physicians are accepting of ambulatory blood pressure monitoring's advantages. Summarizing the studies that deal mainly with hemodialysis patients, there are clear advantages to using more than isolated pre- and posthemodialysis blood pressure readings. If enough predialysis blood pressure readings are taken and averaged, this is a reasonable guide to end-organ damage (ie, left ventricular hypertrophy). Home and ambulatory blood pressure-derived values are complementary, and only this approach can discern any further contribution from diurnal blood pressure elevation. The cross-sectional association between blood pressure and end-organ damage is very weak in end-stage renal disease patients if the blood pressure values are "casual," but the relationship is much stronger when ambulatory blood pressure monitoring-derived measurements are used. One prospective study clearly linked the sustained loss of diurnal blood pressure fall with sleep with progressive left ventricular dilatation. Loss of circadian variation in blood pressure is associated with an increased mortality rate for dialysis patients and for diabetic patients, regardless of diabetes type. The combination of nondipping in renal impairment leads to a high mortality rate. Much more work is needed to dissect out the causes for abnormal diurnal blood pressure rhythm and attempt to modulate this parameter. Obstructive sleep apnea may be a promising target for intervention.

Dietary sodium restriction restores nocturnal reduction of blood pressure in patients with primary aldosteronism

The purpose of this study was to elucidate the effects of dietary sodium restriction on diurnal blood pressure (BP) variation in primary aldosteronism. We studied the diurnal variation in the systemic hemodynamic indices and in baroreflex sensitivity (BRS). In 13 subjects with aldosterone-producing adenomas (2 males; mean age, 39+/-2 years), intra-arterial pressure was monitored telemetrically on a normal salt diet (NaCl 10-12 g/day). Non-dippers were defined as those with a nocturnal reduction in systolic BP (SBP) of less than 10% of daytime SBP. Ten subjects showed a non-dipper pattern. Six of these "non-dippers" underwent repetitive hemodynamic studies on the last day of a 1-week low salt diet regimen (NaCl 2-4 g/day). Stroke volume was determined using Wesseling's pulse contour method, calibrated with indocyanine green dilution. BRS was calculated every 30 min as delta pulse interval/delta SBP on spontaneous variations. Nocturnal reduction of SBP was 4.1% on the normal salt diet. With sodium restriction, urinary sodium excretion decreased from 187+/-8 to 46+/-8 mmol/day, and body weight decreased from 57.9+/-2.1 to 56.6+/-1.9 kg. Night-time BP significantly decreased with dietary modification from 154+/-7/88+/-4 to 140+/-6/78+/-4 mmHg, whereas daytime BP was unaltered. With sodium restriction, cardiac index and stroke index decreased throughout the day. No significant difference was seen in either daytime or nighttime BRS between the two diets. We conclude that the non-dipper pattern is common in patients with an aldosterone-producing adenoma on a normal salt intake, and under such conditions, volume expansion appears to play a major role in the impairment of nocturnal BP reduction.

The influence of work- and home-related stress on the levels and diurnal variation of ambulatory blood pressure and neurohumoral factors in employed women

The purpose of this study was to examine the effects of self-reported perceived stress at work and home on the levels, variation and co-variation of ambulatory blood pressure (BP), pulse rate (PR) and urinary catecholamine, cortisol, and aldosterone excretion measured at work, home and during sleep in women employed outside the home. The subjects of the study were 134 women (mean age 34.4 +/- 9.6 years, range 18 to 64 years) who were employed in managerial, technical or clerical positions at the same work place. Perceived stress at work and home was self-reported on a scale from 0 (low) to 10 (high). BP, PR and the urinary rates of excretion of epinephrine, norepinephrine, cortisol and aldosterone were averaged in the daily work environment from 11 AM to 3 PM, in the daily home environment from approximately 6 PM to 10 PM, and during sleep from approximately 10 PM to 6 AM the following morning. The results showed that systolic and diastolic BP (SBP and DBP) and the rates of urinary catecholamine, cortisol, and aldosterone excretion measured in the work environment were significantly higher than corresponding measurements taken in the home environment. SBP measured at work was also positively correlated with the difference in perceived stress between work and home (p < 0.05). PR (p < 0.001) and the rate of urinary norepinephrine excretion (p < 0.05) measured in the home environment were positively correlated with stress at home. When the subjects were divided into groups based on whether the work or home environment was perceived to be most stressful, women reporting greater stress at work (n=85) had higher work SBP (p < 0.005), work DBP (p < 0.05), and sleep SBP (p < 0.005) than women who perceived the home environment to be more stressful (n=34). There were no differences in the urinary hormonal excretion rates between these perceived-stress groups. Among women with greater perceived stress at home, the home-stress score was positively correlated with sleep SBP level (r = 0.310, p < 0.05), its variation (SD of sleep SBP: r = 0.402, p < 0.01) and home pulse rate ( r= 0.414, p < 0.01). These findings suggest that among employed women, work stress may increase ambulatory BP levels throughout the day, while home stress may induce additional sympathetic activation at home. In addition, they also show that among employed women who perceive greater stress at home than at work, higher home stress levels may also elevate sleep BP levels.

Psychological and physical stress-induced cardiovascular reactivity and diurnal blood pressure variation in women with different work shifts

There is increasing evidence that diurnal blood pressure (BP) variation, in addition to high BP per se, is related to target organ damage and the incidence of cardiovascular events. However, the determinants of diurnal BP variation are not adequately understood. This paper tests the hypothesis that cardiovascular reactivity to acute stress and/or delayed recovery predicts greater diurnal BP variation (i.e., a lower sleep/awake BP ratio). We studied the relationship of diurnal BP variation (assessed by ambulatory BP monitoring) to mental stress (mental arithmetic and anger recall tasks) and physical stress (treadmill)-induced cardiovascular reactivity and recovery in 87 female nurses who worked different shifts. The sleep/awake systolic BP (SBP) ratio was negatively correlated with relative SBP reactivity (maximum SBP increase/baseline SBP: r = -0.21, p = 0.06) and relative stress response (average of SBP during stress/baseline SBP:r = -0.23, p = 0.04) induced by anger recall, while the correlations of the sleep/awake SBP ratio with other parameters of reactivity or recovery in the anger recall or mental arithmetic task were not significant. When subjects were divided into day-shift workers (n=54) and night-shift workers (n = 33), the sleep/awake SBP ratio was negatively correlated with relative SBP reactivity (r = -0.41, p = 0.02) and relative stress response of SBP (r = -0.48, p = 0.006) induced by anger recall, and positively correlated with recovery rate (r = 0.34, p = 0.06) in the latter group, while these correlations were not significant in the former group. The sleep/awake SBP ratio was inversely correlated with the exercise-induced SBP increase in the day-shift workers (r = -0.30, p = 0.03), while this association was not found in the night-shift workers. In conclusion, cardiovascular reactivity triggered by psychological and physical stress in the laboratory may be a weak, but significant, determinant of diurnal BP variation; in addition, work shift (day or night) appears to moderate the relationship between these two pressor mechanisms.

A simple oscillometric technique for determining new indices of arterial distensibility

Recently, oscillometric devices have been developed that can measure blood pressure in the extremities and analyze pulse volume record. On the basis of the extremity pulse volume record, these devices can automatically determine three types of simply measured pulse wave velocity (PWV) (brachial PWV: heart to right upper arm; R-PWV: right upper arm-right ankle; and L-PWV: right upper arm-left ankle). The percent mean pulse volume record (%MPVR=the height that bisects the area of the pulse volume record/pulse pressure X100), a quantitative index of right brachial pulse volume record, can also be determined. To evaluate the usefulness of these new indices, we studied 1,067 consecutive subjects undergoing health checkups (648 men, 419 women; mean age, 50 +/- 9 years). In both sexes, age correlated positively with simply measured PWVs (men, brachial PWV: r=0.46, p<0.0001; R-PWV: r=0.46, p<0.0001; L-PWV: r=0.47, p<0.0001; women, brachial PWV: r=0.37, p<0.0001; R-PWV: r=0.47, p<0.0001; L-PWV: r=0.48, p<0.0001) and correlated negatively with %MPVR (men: r=-0.40, p<0.0001; women: r=-0.45, p<0.0001). Simply measured PWVs and %MPVR were significantly correlated with mean blood pressure. In a separate group of 60 patients, simply measured PWVs correlated positively with carotid PWV (heart to carotid) derived from an elastic vessel (brachial PWV: r=0.76, p<0.0001; R-PWV: r=0.43, p<0.01; L-PWV: r=0.43, p<0.01). %MPVR correlated negatively with carotid PWV (r=-0.35, p<0.01). In conclusion, simply measured PWVs and %MPVR are easier to determine than conventional PWV and may be useful as new indices of age-related changes in arterial distensibility.