Sympathetic overactivity and 24-hour blood pressure pattern in hypertensives with chronic renal failure

Rostral ventrolateral medulla neuron activity is suppressed by Klotho and stimulated by FGF23 in newborn Wistar rats

Hypertension often occurs in patients with chronic kidney disease (CKD). Considering the decrease in serum Klotho and increase in serum FGF23 levels in such patients, decreased Klotho and increased FGF23 levels were thought to be associated with hypertension. Presympathetic neurons at the rostral ventrolateral medulla (RVLM) contribute to sympathetic activity and regulation of blood pressure. Therefore, we hypothesized that Klotho would reduce the activities of RVLM neurons and FGF23 would stimulate them. Accordingly, this study examined the effects of Klotho and FGF23 on bulbospinal neurons in the RVLM. We used a brainstem-spinal cord preparation to record from RVLM presympathetic neurons and to evaluate the effects of Klotho and FGF23 on firing rate and membrane potentials of these neurons. Our results showed that Klotho-induced RVLM neuron hyperpolarization, while ouabain, a Na⁺/K⁺-ATPase inhibitor, suppressed the effects of Klotho on such neurons. Moreover, FGF23 induced RVLM neuron depolarization, while SU5402, an FGF23 receptor (FGFR1) antagonist, induced RVLM neuron hyperpolarization. Histological examinations revealed that Klotho, Na⁺/K⁺-ATPase, FGF23, and FGFR1 were present in RVLM neurons and that Klotho was localized in the same neurons as FGFR1. These results suggest that Klotho and FG23 regulate the activity of RVLM neurons. Klotho may reduce the activity of RVLM neurons via stimulating Na⁺/K⁺-ATPase on those neurons while FGF23 may activate those neurons via FGFR1.

Heart rate and blood pressure variability in children with chronic kidney disease: a report from the CKiD study

BACKGROUND

Autonomic nervous system dysfunction and sympathetic nervous system over-activity play important roles in the development of hypertension associated with chronic kidney disease (CKD). In adults, increased blood pressure variability (BPV) appears to be directly related to sympathetic over-activity with increased risk of end-organ damage and cardiovascular events. Decreased heart rate variability (HRV) has been observed in adults with CKD, and is an independent predictor of mortality.

METHODS

The purpose of this study was to evaluate BPV and HRV in pediatric patients enrolled in the Chronic Kidney Disease in Children Study. Ambulatory blood pressure monitoring data were available for analysis of 215 person-visits from 144 children that were not receiving antihypertensive medications.

RESULTS

BPV and HRV were determined by standard deviation and coefficient of variation for heart rate and systolic and diastolic blood pressure for each patient averaged for wake/sleep periods during 24-h monitoring. Uniformly lower values were displayed during sleep versus wake periods: BPV was 20 % lower during sleep (p < 0.001) and HRV was 30 % lower during sleep (p < 0.001). A significant increase in systolic BPV was observed in hypertensive children compared to children with normal blood pressure (6.9 %, p = 0.009). Increased diastolic BPV was detected among hypertensive children during sleep period compared to children with normal blood pressure (11.5 %, p = 0.008). There was a significant decrease in HRV in hypertensive compared to normotensive children (-8.2 %, p = 0.006).

CONCLUSIONS

These findings are similar to those in adult patients and may underscore childhood origin and natural progression of adverse cardiovascular outcomes in adults with CKD.

Circadian variation of blood pressure: the basis for the chronotherapy of hypertension

Ambulatory blood pressure (BP) measurements present a close correlation with target organ damage and cardiovascular events, including myocardial infarction, stroke and cardiovascular mortality. With the use of this measurement technique, a significant circadian variation has been shown to characterize BP. This circadian BP variation, although affected by a variety of external factors, represents the influence of internal factors such as ethnicity, gender, autonomic nervous system tone, vasoactive hormones, and hematologic and renal variables. In most individuals, BP presents a morning increase, a small post-prandial valley, and a deeper descent during nocturnal rest. However, under certain pathophysiological conditions, the nocturnal BP decline may be reduced or even reversed. This cannot be determined by traditional clinical or home BP assessments. Subjects with a diminished nocturnal BP decline (non-dipper pattern) have a significantly worse prognosis than the ones with a normal dipper pattern. In particular, the non-dipper circadian BP pattern represents a risk factor for left ventricular hypertrophy, microalbuminuria, cerebrovascular disease, congestive heart failure, vascular dementia and myocardial infarction. The normalization of the circadian BP pattern to a dipper profile is a novel therapeutic goal, and accumulating medical evidence suggests this can delay the progression towards the renal and cardiovascular pathology known to be a consequence of the non-dipper BP pattern. The features of the circadian BP profile have direct implications for improving the drug-delivery of antihypertensive therapies as well as the qualification of patients for medication trials and assessment.

Blood pressure and progression of chronic kidney disease: Importance of systolic, diastolic, or diurnal variation

Several studies show that systolic blood pressure is an important predictor of renal disease progression, just as it is linked with cardiovascular consequences in hypertension. In contrast, particularly in older patients, diastolic blood pressure was not independently associated with risk of kidney disease progression in the same studies. Pulse pressure has been shown to be equivalent in predicting renal outcomes, but might not have added value after adjusting for systolic blood pressure. Several cross- sectional studies present a strong correlation of ambulatory blood pressure monitoring values with microalbuminuria, compared with office-based blood pressure measurements. Small, prospective studies have shown an association between loss of nocturnal blood pressure decline and outcomes, including microalbuminuria, accelerated kidney disease progression, and mortality.

Efficacy and safety of doxazosin GITS in hypertensive renal transplant patients: comparison of 8 and 4 mg

BACKGROUND

Hypertension (HT), a prevalent complication in renal transplant patient (RT), must be accurately treated because cardiovascular disease is the leading cause of death and of chronic graft dysfunction. Sympathetic activity may contribute to HT in RT, yielding the rationale to suspect that doxazosin, an alpha1-adrenergic receptor inhibitor, may lower blood pressure (BP). The aim of this study was to evaluate the efficacy and safety of doxazosin GITS (4 and 8 mg) in RT.

METHODS

Twenty-three hypertensive RT received doxazosin 4 mg once daily for 4 weeks (W4) followed by a 4-week washout (W0) and 17/23 treated with doxazosin 8 mg for 4 more weeks (W8) due to persistent HT. All patients underwent 24-hour ambulatory blood pressure monitoring (ABPM) after W0, W4, and W8. Laboratory tests were performed, adverse events recorded, and prostatic symptomatology examined. Statistical analysis included Saphiro-Wilks, Student t, ANOVA, Wilcoxon, or Friedman tests.

RESULTS

The systolic, diastolic, and mean BP were significantly lowered at W4 in awake (P<.001) and 24 hour period (P<.005) but not sleep recordings. Doxazosin 8 mg had no significant additional effect to lower BP at any period. Normotension was reached in 13% and 21.7% of patients at W4 and W8, respectively. Palpitations were the only reported adverse event after treatment (incidence similar to placebo). There was no significant change in the laboratory values.

CONCLUSIONS

Doxazosin (-4 mg) effectively decreased BP in awake and 24-hour periods without a significant improvement during sleep. A double dose of the drug added little benefit. Optimal BP was reached by an insufficient number of patients. Doxazosin proved to have a good tolerance and safe profile. This results suggest that doxazosin should be considered a good add-on treatment to other antihypertensive drugs in RT.

[Analysis of heart rate as a risk factor associated with the progression of chronic renal failure]

BACKGROUND

An increased heart rate is associated with an increased risk of cardiovascular and non-cardiovascular death. However, the possible relationship between heart rate and the rate of progression of renal disease has not been assessed so far.

PATIENTS AND METHOD

Twenty-four-hour ambulatory blood pressure and heart rate recordings at baseline conditions were obtained in 24 patients with non-diabetic chronic renal failure and hypertension. The rate of progression of renal disease was estimated on the basis of the slope of the reciprocal of serum creatinine concentration against time.

RESULTS

After a mean follow-up of 38 months, the rate of progression of renal failure was 0.004 (0.039) dL/mg/month. Progression of renal disease showed no correlation with baseline ambulatory systolic or diastolic blood pressures, and did not differ between dipper and non-dipper patients. Twenty-four-hour (r = 0.40, p = 0.05) and day-time (r = 0.534, p = 0.007) heart rates showed a relationship with the progression of renal failure. Proteinuria displayed a correlation with night-time heart rate (r = 0.405, p = 0.05) but not with the progression of renal failure.

CONCLUSIONS

Baseline ambulatory heart rate, especially day-time heart rate, is associated with the decline of renal function in non-diabetic patients with chronic renal failure, suggesting that heart rate is a risk factor (or marker) for renal disease progression. Prospective controlled studies with a larger sample of patients are needed to confirm these findings and to investigate the possible mechanisms involved in this association.

Relationship between physical activity and blood pressure in dipper and non-dipper hypertensive patients

BACKGROUND

The lack of nocturnal decline in blood pressure has been associated with an increase in end-organ damage and cardiovascular events, although results remain controversial, partly because of the inability to reproduce correctly, over time, the classification of patients into dippers and non-dippers. Moreover, the non-dipping status has been frequently related to an increase in nocturnal activity, differences in quality of sleep, or both.

OBJECTIVE

To assess the relationship between activity and blood pressure in patients with hypertension.

METHODS

We studied 306 mild-to-moderately hypertensive patients (130 men), 53.7 +/- 14.0 years of age (mean +/- SD). Blood pressure and heart rate were measured for 48 consecutive hours, at 20-min intervals during the day and at 30-min intervals at night, using an ambulatory device, and physical activity was simultaneously evaluated at 1-min intervals by wrist actigraphy. Circadian parameters of blood pressure, heart rate and activity established by population multiple-components analysis were compared between dippers and non-dippers, by non-parametric testing. Diurnal and nocturnal means of blood pressure and activity were computed for each patient according to individual resting hours determined by actigraphy, and compared among groups by analysis of variance.

RESULTS

Despite highly statistically significant differences between dippers and non-dippers with respect to nocturnal means and in each hourly nightly mean of blood pressure, there were no differences between them for the same parameters during activity, whether or not the patients were receiving medication at the time of monitoring. The average duration of sleep and the 24-h mean and standard deviation of activity were also similar between the groups.

CONCLUSIONS

The highly significantly different circadian variation in blood pressure between dippers and non-dippers with essential hypertension is not related to a significant increase in nocturnal physical activity. Differences in blood pressure could, however, be related to the absence of 24-h therapeutic coverage in most non-dipper patients receiving antihypertensive medication.

Practice-based randomized controlled-comparison clinical trial of chiropractic adjustments and brief massage treatment at sites of subluxation in subjects with essential hypertension: pilot study

OBJECTIVE

To determine the feasibility of conducting a randomized clinical trial in the private practice setting examining short- and long-term effects of chiropractic adjustments for subjects with essential hypertension compared with a brief soft tissue massage, as well as a nontreatment control group.

DESIGN

Randomized controlled-comparison trial with 3 parallel groups.

SETTING

Private practice outpatient chiropractic clinic.

PATIENTS

Twenty-three subjects, aged 24 to 50 years with systolic or diastolic essential hypertension.

INTERVENTIONS

Two months of full-spine chiropractic care (ie, Gonstead) consisting primarily of specific-contact, short-lever-arm adjustments delivered at motion segments exhibiting signs of subluxation. The massage group had a brief effleurage procedure delivered at localized regions of the spine believed to be exhibiting signs of subluxation. The nontreatment control group rested alone for a period of approximately 5 minutes in an adjustment room.

MAIN OUTCOME MEASURES

Cost per enrolled subject, as well as systolic and diastolic blood pressure (BP) measured with a random-0 sphygmomanometer and patient reported health status (SF-36). Pilot study outcome measures also included an assessment of cooperation of subjects to randomization procedures and drop-out rates, recruitment effectiveness, analysis of temporal stability of BPs at the beginning of care, and the effects of inclusion/exclusion criteria on the subject pool.

RESULTS

Thirty subjects enrolled, yielding a cost of $161 per enrolled subject. One subject was later determined to be ineligible, and 6 others dropped out. In both the chiropractic and massage therapy groups, all subjects were classified as either overweight or obese; in the control group there were only 2 classified as such. SF-36 profiles for the groups were similar to that of a normal population. The mean change in diastolic BP was -4 (95% confidence interval [CI]: -8.6, 0.5) in the chiropractic care group, 0.5 (95% CI: -3.5, 4.5) in the brief massage treatment group, and -4.9 (95% CI: -9.7, -0.1) in the no treatment control group. At the end of the study period, this change was -6.3 (95% CI: 13.1, 0.4), -1.0 (95% CI: -7.5, 15.6), -7.2 (95% CI: -13.3, -1.1) in the 3 study groups. The mean improvements in the chiropractic care and no treatment control groups remained consistent over the follow-up period.

CONCLUSIONS

This pilot study elucidated several procedural issues that should be addressed before undertaking a full-scale clinical trial on the effects of chiropractic adjustments in patients with essential hypertension. A multidisciplinary approach to recruitment may need to be used in any future efforts because of the limited subject pool of patients who have hypertensive disease but are not taking medications for its control. Measures need to be used to assure comparable groups regarding prognostic variables such as weight. Studies such as these demonstrate the feasibility of conducting a full-scale 3-group randomized clinical trial in the private practice setting.

Self-measured systolic blood pressure in the morning is a strong indicator of decline of renal function in hypertensive patients with non-diabetic chronic renal insufficiency

While blood pressure is a recognized major determinant of renal function deterioration, the role of self blood pressure measurement (BPM) in predicting the loss of renal function in hypertensive patients with chronic renal insufficiency (CRI) has not been adequately addressed. One hundred and thirteen patients (F/M: 46/67; 56 +/- 1 years) with CRI (mean serum creatinine: 1.87 +/- 0.08; range: 1.4 to 3.5 mg/dl; average urinary protein excretion: 1.2 +/- 0.2 g/24 hrs.) were followed for 3 years. The record of renal biopsy revealed that 74 patients had IgA nephropathy, 16 had chronic glomerulonephritis, and 6 had membranous nephropathy, while 17, unbiopsied patients had underlying renal disease of unknown origin. Self BPM were made at regular intervals throughout the course of the study. All recorded blood pressures were included in a stepwise multiple regression analysis in which the decline in GFR per year was the dependent variable. Patients were primarily treated with a combination of amlodipine (5 to 20 mg daily), a calcium antagonist, and benazepril (2.5 to 5 mg daily), an ACE inhibitor in an effort to reduce their blood pressure at the office to < 130/85 mmHg. The simple correlation between blood pressures (i.e., office, home morning and home evening) and the decline in GFR were all statistically significant. The correlation coefficients of determination for this model were as follows: r = 0.64 for home morning SBP; 0.43 for office SBP; 0.39 for office DBP; and 0.38 for home morning DBP. The level of urinary protein excretion did not correlate with the decline in GFR. These data suggest that self BPM improves prognostic ability in hypertensive patients with CRI.

Blood pressure reduction in the morning yields beneficial effects on progression of chronic renal insufficiency with regression of left ventricular hypertrophy

Self-monitoring values of blood pressure may better reflect the average long-term blood pressure value than sporadic measurements in the physician's office and be more useful for blood pressure control. In the present study, we compared the results of self-monitoring of blood pressure values, especially in the morning, with office blood pressure, and related these to progression of chronic renal insufficiency and left ventricular hypertrophy (LVH). Thirty-four patients were selected from 316 subjects with chronic renal insufficiency (average serum creatinine 1.72 +/- 0.15 mg/dl, mean age 52.6 +/- 3.5 yrs) in accordance with the following criteria (1) office blood pressure was less than 140/90 mmHg, (2) blood pressure was controlled with amlodipine (5-20 mg/day) combined with benazepril (2.5 mg/day), (3) morning blood pressure was greater than 150/90 mmHg at 6-9 AM and (4) LVH had been determined by echocardiography (posterior wall thickness; PWT > or = 12 mm). The patients were assigned to 2 groups at random and were given: (1) guanabenz (GB; 2-8 mg at I I PM, n = 17) or (2) placebo (n = 17). Two years later, the average blood pressure of both groups as measured in the office was not significantly different: however, BP in the morning was significantly reduced from 158 +/- 6 to 134 +/- 4 mmHg in GB treated group (P< 0.001). In 14 of 17 patients in GB treated group, LVH resolved and there was only mild progression of nephropathy (serum creatinine: 1.69 +/- 0.18 to 1.81 +/- 0.19 mg/dl). In 12 of 14 patients in placebo group, whose morning blood pressure remained at greater than 150/90 mmHg, LVH was retained and there was moderate progression of nephropathy (serum creatinine: 1.73 +/- 0.14 to 2.62 +/- 0.50mg/dl). From these results, it is suggested that antihypertensive treatment with combination therapy based on self-monitoring BP is cardio-renoprotective in patients with chronic renal insufficiency and LVH.

Sympathetic nervous system and chronic renal failure

The aim of this work was to review evidence on the role of the sympathetic nervous system (SNS) in chronic renal failure (CRF). Three main points are discussed: 1) SNS and pathogenesis of arterial hypertension; 2) SNS and cardiovascular risk; 3) implication of SNS in arterial hypotension during hemodialysis. Several lines of evidence indicate the presence of a sympathetic hyperactivity in CRF, and its relationship with arterial hypertension. It is suggested that diseased kidneys send afferent nervous signals to central integrative sympathetic nuclei, thus contributing to the development and maintenance of arterial hypertension. The elimination of these impulses with nephrectomy could explain the concomitant reduction of blood pressure. Several experiments confirmed this hypothesis. Regarding SNS and cardiovascular risk, some data suggest that reduced heart rate variability identifies an increased risk for both all causes and sudden death, independently from other recognized risk factors. Symptomatic hypotension is a common problem during hemodialysis treatment, occurring in approximately 20-30% of all hemodialysis sessions and is accompanied by acute withdrawal of sympathetic activity, vasodilation and relative bradicardia. This reflex is thought to be evoked by vigorous contraction of a progressively empty left ventricle, activating cardiac mechanoceptors. This inhibits cardiovascular centers through vagal afferents, and overrides the stimulation by baroreceptor deactivation. Alternative explanations include cerebral ischemia and increased production of nitric oxide, which inhibit central sympathetic activity. It is hoped that therapies aimed at modulating sympathetic nerve activity in patients with CRF will ameliorate their prognosis and quality of life.

What is hypertension in chronic haemodialysis? The role of interdialytic blood pressure monitoring

BACKGROUND

Hypertension in chronic haemodialysis patients contributes significantly to morbidity and mortality. Treatment decisions are usually based on predialysis readings, which may not accurately reflect control during the interdialytic period.

METHODS

We studied 40 randomly selected subjects on haemodialysis and compared readings by different methods at set times during the dialysis session with the 48-h interdialytic ambulatory readings. Conventional sphygmomanometer, automated Dinamap and Tm 2421(A&D) ambulatory monitor were used for BP measurements.

RESULTS

Conventional sphygmomanometry and self measured automatic readings (Dinamap) were highly correlated (systolic r=0.93, P<0.001; diastolic r=0.90, P<0.001). Mean blood pressure on arrival ((PreC(0)) 158 mmHg systolic, 80 mmHg diastolic and 106 mmHg mean) significantly overestimated the mean ambulatory reading during the 6 h prior to attendance ((preAm(6h)) systolic 147 (P<0.01), diastolic 75 (P<0.01), mean 99 (P<0.01)). Fifteen patients (41%) demonstrated a marked difference (>20/10 mmHg) between the PreC(0) and preAm(6h) (white-coat effect) persisting in seven patients (19%) after a period of rest 10 min predialysis (preC(10)) and present even in self-recorded Dinamap readings. There was a significant negative relationship between the systolic rise and the number of months on dialysis (P<0.05). Mean ambulatory BP on interdialytic day 2 was significantly greater than on day 1 whereas the awake-sleep differences were less on day 2 than day 1, both perhaps reflecting differences in volume status. The 20 min post-dialysis measurement (PoC(20)) for systolic, diastolic, and mean, unlike predialysis (PreC(0) and preC(10)), onset (onC) and end of dialysis readings (enC) did not differ significantly from 48 h interdialytic means.

CONCLUSIONS

The best representation of interdialytic pressure was the 20-min post-dialysis reading. Walk-in predialysis pressures overestimate mean interdialytic pressures due to a high incidence of white-coat effect, which shows some habituation with time on dialysis. Ambulatory monitoring has a role in evaluating persistent poor blood pressure control in haemodialysis patients.

Ambulatory blood pressure monitoring and interdialytic weight gain in children receiving chronic hemodialysis

Volume overload appears to induce hypertension in hemodialysis patients, yet studies of the effect of hydration status on interdialytic blood pressure (BP) have yielded contradictory results. We measured interdialytic BP by ambulatory BP monitoring (ABPM) during inpatient fluid restriction in 12 children receiving chronic hemodialysis to describe the overall BP pattern and to determine the effect of weight gain on BP change. Weight was measured on admission and four times each day. For each weight, casual BP was measured and compared with the mean of 3 hours of ABPM surrounding the weight measurement. Sleep BP decreased from daytime BP by 6% for systolic BP (SBP) and 11% for diastolic BP (DBP). Sleep loads were greater than daytime loads (P < 0.01) for SBP (53% v 28%) and DBP (57% v 27%). Overall, 58% (7 of 12) of the patients had sleep SBP load greater than 50%, and 67% (8 of 12) of the patients had sleep DBP load greater than 50%. Casual and ABPM measurements of BP showed moderate correlations for SBP (r = 0.51) and DBP (r = 0.46) and mean differences between methods of 6.3 +/- 13.2 mm Hg and -1.4 +/- 12.6 mm Hg, respectively. Increases in interdialytic weight were positively associated with increases in SBP (r = 0.41; P < 0.001), and interdialytic BP changes varied closely with corresponding weight changes. We conclude that in children receiving chronic hemodialysis: (1) sleep BP decreases are attenuated and sleep BP loads are elevated, (2) casual BP correlates poorly with ABPM, and (3) interdialytic weight and BP are related.

Ambulatory blood pressure monitoring is a useful clinical tool in nephrology

Hypertension is a key factor in the genesis and deterioration of many renal diseases and is also a risk factor for death in patients with end-stage renal disease. However, the standard methods of measurement are prone to variability, especially in patients undergoing dialysis. The technique of ambulatory blood pressure monitoring allows a better assessment of overall blood pressure levels and promises to assume a bigger role in the care of renal patients. Ambulatory blood pressure monitoring is widely used in hypertension trials, and the reports of several consensus meetings on the clinical uses of ambulatory blood pressure monitoring have been published. Two similar validation protocols now exist for ambulatory blood pressure monitors, and tables of population-based normal blood pressures for age and gender are available. The available evidence suggests that ambulatory blood pressure compared with blood pressure measured in the physician's office is better correlated to left ventricular mass in subjects with chronic renal disease. Furthermore, studies in subjects with chronic renal disease and those undergoing renal replacement therapy show that blood pressure control is suboptimal in many patients and that nocturnal blood pressure is generally higher than in control subjects. Further insights into overall blood pressure behavior in this population will certainly emerge in the future.