Circadian variation of blood pressure and neurohumoral factors during the acute phase of stroke

Circadian Factors in Stroke: A Clinician's Perspective

Stroke remains one of the leading causes of mortality and long-term and permanent disability worldwide despite technological innovations and developments in pharmacotherapy. In the last few decades, the growing data have evidenced the role of the circadian system in brain vulnerability to damage, the development and evolution of stroke, and short-term and long-term recovery. On the other hand, the stroke itself can affect the circadian system via direct injury of specific brain structures involved in circadian regulation (i.e., hypothalamus, retinohypothalamic tracts, etc.) and impairment of endogenous regulatory mechanisms, metabolic derangement, and a neurogenic inflammatory response in acute stroke. Moreover, the disruption of circadian rhythms can occur or exacerbate as a result of exogenous factors related to hospitalization itself, the conditions in the intensive care unit and the ward (light, noise, etc.), medication (sedatives and hypnotics), and loss of external factors entraining the circadian rhythms. In the acute phase of stroke, patients demonstrate abnormal circadian variations in circadian biomarkers (melatonin, cortisol), core body temperature, and rest-activity patterns. The approaches aimed at the restoration of disrupted circadian patterns include pharmacological (melatonin supplementation) and non-medication (bright light therapy, shifting feeding schedules, etc.) interventions; however, their effects on short- and long-term recovery after stroke are not well understood.

Assessment of brain natriuretic peptide and copeptin as correlates of blood pressure in chronic hypertensive pregnant women

BACKGROUND

Hypertensive disorders of pregnancy including preexisting (or chronic) hypertension are the most common complication encountered during pregnancy that contribute significantly to maternal and perinatal morbidity and mortality. Brain natriuretic peptide (BNP) and copeptin have been investigated as biomarkers in various hypertensive disorders, but studies of their clinical value in chronic hypertensive pregnant women are sparce. This study aimed to assess the levels of BNP and copeptin in chronic hypertensive pregnant women and investigate their correlation with blood pressure (BP) in chronic hypertensive pregnant women in South Western Nigeria.

METHODS

One hundred and sixty consenting pregnant women in their third trimester of pregnancy, grouped into those with chronic hypertension (n = 80) and normotensive (n = 80), were recruited for this cross-sectional study. Age and clinical characteristics were obtained, and blood was aseptically drawn for BNP and copeptin measurement using enzyme-linked immunosorbent assay. Data was analyzed with IBM SPSS ver. 20.0. Data was analyzed using Student t-test, chi-square, and Pearson correlation test as appropriate. Statistical significance was set at P < 0.05.

RESULTS

The mean systolic BP (SBP) and diastolic BP (DBP) were significantly higher in pregnant women with chronic hypertension (158.30 ± 3.51 and 105.08 ± 2.47 mmHg, respectively) compared with normotensive pregnant women (100.72 ± 3.02 and 70.29 ± 1.96 mmHg, respectively). The mean levels of BNP and copeptin were higher in pregnant women with chronic hypertension (57.26 ± 3.65 pg/mL and 12.44 ± 1.02 pmol/L, respectively) compared with normotensive pregnant women (49.85 ± 2.44 pg/mL and 10.25 ± 1.50 pmol/L, respectively) though not statistically significant. Correlations observed between SBP and DBP with levels of BNP (r = 0.204, P = 0.200; r = 0.142, P = 0.478) and copeptin (r = - 0.058, P = 0.288; r = 0.045, P = 0.907) were not statistically significant.

CONCLUSIONS

There was no association between BP and the levels of BNP and copeptin in pregnant women with chronic hypertension who were already on antihypertensive treatment, with the implication that antihypertensive treatment may modulate BNP and copeptin release despite significantly elevated BP levels.

Prognostic Value of Circadian Brain Temperature Rhythm in Basal Ganglia Hemorrhage After Surgery

Introduction

Intracerebral hemorrhage (ICH) is associated with high mortality and morbidity rates. However, both the rhythmic variation and prognostic value of brain temperature after ICH remain unknown. In this study, we investigated brain temperature rhythm and its prognostic value for post-operative mortality and long-term functional outcomes in patients with ICH.

Methods

Post-operative diurnal brain temperature patterns at the basal ganglion are described. Following surgery for ICH, 78 patients were enrolled, and intracranial pressure and brain temperature were monitored using a fiber optic device. Brain temperature mesor, amplitude, and acrophase were estimated from the recorded temperature measurements, using cosinor analysis, and the association between these patterns and clinical parameters, mortality, and functional outcomes at the 12-month follow-up were examined.

Results

According to cosinor analysis, brain temperature in 55.1% of patients showed a circadian rhythm within 72 h post-surgery. The rhythm-adjusted mesor of brain temperature (± standard deviation) was 37.6 (± 0.7) °C, with a diminished mean amplitude. A temperature acrophase shift was also observed. Multivariate logistic regression analysis revealed that initial age and circadian rhythm of brain temperature appeared to be predictive and prognostic of functional outcomes. Further, patients with higher brain temperature mesor were more likely to survive than those with a lower mesor.

Conclusion

For patients with ICH, brain temperature rhythm analysis is an improved prognostic tool for mortality and functional outcome predictions.

Sleep and Cardiovascular Risk

Sleep is essential for healthy being and healthy functioning of human body as a whole, as well as each organ and system. Sleep disorders, such as sleep-disordered breathing, insomnia, sleep fragmentation, and sleep deprivation are associated with the deterioration in human body functioning and increased cardiovascular risks. However, owing to the complex regulation and heterogeneous state sleep per se can be associated with cardiovascular dysfunction in susceptible subjects. The understanding of sleep as a multidimensional concept is important for better prevention and treatment of cardiovascular diseases.

A prospective study of brain natriuretic peptide levels in three subgroups: Stroke with hypertension, stroke without hypertension, and hypertension alone

Aim:

To study brain natriuretic peptide (BNP) levels in three subgroups: patients having stroke with hypertension (HT), those having stroke without HT, and those with HT alone. We also tried to identify whether BNP levels predict the length of stay in hospital and mortality.

Materials and Methods:

The groups were formed by patients who had been admitted to the emergency department in the first 4–12 h after the onset of symptoms. There were 30 stroke patients with a history of HT (group I), 30 stroke patients without a history of HT (group II), and 20 HT patients without stroke (group III). Patients with congestive heart failure, chronic cor pulmonale, severe valvular heart disease, chronic renal failure, liver insufficiency, diabetes mellitus, atrial fibrillation, and those with a history of stroke were excluded from the study since these diseases can affect the plasma BNP levels.

Results:

The demographic characteristics, except the age distribution, were similar among the groups. The mean BNP levels in the three groups were 168.8 ± 223.9 pg/ml, 85.0 ± 75.1 pg/ml, and 84.8 ± 178.3 pg/ml, respectively. The differences between the groups were statistically significant.

Conclusion:

The mean BNP levels were affected by HT and/or stroke. The simultaneous presence of HT and stroke results in a more significant increase BNP than the presence of either stroke or HT alone. When diseases that can affect the plasma BNP levels are excluded, the BNP levels in stroke patients without a history of HT are similar to the levels seen in patients with only HT.

Factors Affecting the B-Type Natriuretic Peptide Levels in Stroke Patients

Introduction: This study aims to evaluate the relationship between increased B-type natriuretic peptide (BNP) levels in stroke patients and clinical parameters such as age, sex, medical history, blood pressure, Glasgow Coma Score (GCS) and National Institutes of Health Stroke Scale (NIHSS). Materials and Methods: This is a prospective study of 123 stroke patients at the Emergency Department. The patients were divided into 3 groups according to the NIHSS scores. The analysis of the mean difference between continuous variables and plasma BNP levels was assessed using the Mann-Whitney and Kruskal-Wallis. Spearman correlation analysis was performed for BNP and other clinical parameters. Results: The BNP levels of patients who had a medical history of hyperlipidaemia, chronic obstructive pulmonary disease, diabetes mellitus and coronary artery disease were significantly higher than in patients without these diseases. Patients who had atrial fibrillation (AF) in their electrocardiography had significantly higher BNP levels than patients with sinus rhythm. A positive correlation was found between plasma BNP levels with age, blood urea nitrogen (BUN) and NIHSS and a negative correlation was found between plasma BNP levels and GCS. There was a significant difference between the BNP levels of NIHSS groups. Conclusion: We consider that plasma BNP levels could help us in interpreting the general clinical severity, functional capacity and clinical progress of stroke patients at the time of admission in the Emergency Department. In evaluating the high BNP levels in stroke patients, we must keep in mind that age, AF, BUN and medical history can affect the BNP levels. Key words: Emergency Department, Progress, Relationship

Ischemic stroke destabilizes circadian rhythms

BACKGROUND

The central circadian pacemaker is a remarkably robust regulator of daily rhythmic variations of cardiovascular, endocrine, and neural physiology. Environmental lighting conditions are powerful modulators of circadian rhythms, but regulation of circadian rhythms by disease states is less clear. Here, we examine the effect of ischemic stroke on circadian rhythms in rats using high-resolution pineal microdialysis.

METHODS

Rats were housed in LD 12:12 h conditions and monitored by pineal microdialysis to determine baseline melatonin timing profiles. After demonstration that the circadian expression of melatonin was at steady state, rats were subjected to experimental stroke using two-hour intralumenal filament occlusion of the middle cerebral artery. The animals were returned to their cages, and melatonin monitoring was resumed. The timing of onset, offset, and duration of melatonin secretion were calculated before and after stroke to determine changes in circadian rhythms of melatonin secretion. At the end of the monitoring period, brains were analyzed to determine infarct volume.

RESULTS

Rats demonstrated immediate shifts in melatonin timing after stroke. We observed a broad range of perturbations in melatonin timing in subsequent days, with rats exhibiting onset/offset patterns which included: advance/advance, advance/delay, delay/advance, and delay/delay. Melatonin rhythms displayed prolonged instability several days after stroke, with a majority of rats showing a day-to-day alternation between advance and delay in melatonin onset and duration. Duration of melatonin secretion changed in response to stroke, and this change was strongly determined by the shift in melatonin onset time. There was no correlation between infarct size and the direction or amplitude of melatonin phase shifting.

CONCLUSION

This is the first demonstration that stroke induces immediate changes in the timing of pineal melatonin secretion, indicating that cortical and basal ganglia infarction impacts the timing of melatonin rhythms. The heterogeneous direction and amplitude of melatonin shifts suggests that the upstream regulation of hypothalamic timekeeping is likely anatomically diffuse and mechanistically complex. Finally, our study exemplifies the use of pineal microdialysis to evaluate the effect of neurological diseases on circadian function.

N-terminal pro-brain natriuretic peptide levels are elevated in patients with acute ischemic stroke

Brain natriuretic peptide (BNP) is a counterregulatory hormone released by the ventricles of the heart. Its main actions are natriuresis and vasodilation. The authors studied N-terminal pro-brain natriuretic peptide (NT-proBNP) levels soon after an acute ischemic stroke. They compared plasma NT-proBNP concentrations in 30 patients with an acute ischemic stroke with those of 30 controls. The 2 groups were adjusted for age and gender, and there were no significant differences in vascular risk factors and left ventricular systolic and diastolic function. Venous samples were collected within the first 11.8 +/-1.2 hours after the onset of symptoms and again on day 6. Brain computed tomography/magnetic resonance imaging (CT/MRI) was performed on the same days (day 0 and day 6) in order to assess the site (carotid or vertebrobasilar), cause (atherothrombotic, cardioembolic, or lacunar), and size (large, medium, or small) of the brain infarct. NT-proBNP levels were elevated in patients with acute stroke (129.9 +/-9.9 fmol/mL) compared with the controls (90.8 +/-6.3 fmol/mL, p <0.05). These levels remained elevated at day 6 (113.5 +/-13.0 fmol/mL). NT-proBNP at admission was significantly higher in cardioembolic compared with atherothrombotic infarctions. There was no correlation between circulating NT-proBNP and stroke topography, infarct size, or severity as assessed by the National Institutes of Health Stroke Scale (NIHSS) at any of the 2 time points (admission and day 6). NT-proBNP levels were raised in patients with acute ischemic stroke; this effect persisted until day 6. The authors suggest that neurohumoral activation occurs in patients with acute ischemic stroke, either reflecting a counterbalancing vasodilating response to the cerebral ischemia or direct myocardial dysfunction.

Natriuretic Peptides and Mortality After Stroke

Background and Purpose— Measurement of natriuretic peptides provides prognostic information in various patient populations. The prognostic value of natriuretic peptides among patients with acute stroke is not known, although elevated peptide levels have been observed.

Methods— A series of 51 patients (mean age, 68±11years) with first-ever ischemic stroke underwent a comprehensive clinical examination and measurements of plasma atrial natriuretic peptides (N-ANP) and brain natriuretic peptides (N-BNP) in the acute phase of stroke. The patients were followed-up for 44±21 months. Risk factors for all-cause mortality were assessed. Control populations, matched for gender and age, consisted of 51 patients with acute myocardial infarction (AMI) and 25 healthy subjects.

Results— Plasma concentrations of N-ANP (mean±SD, 988±993 pmol/L) and N-BNP (751±1608 pmol/L) in the stroke patients were at the same level as those in the AMI patients (NS for both), but significantly higher than those of the healthy subjects (358±103 pmol/L, P <0.001 and 54±26 pmol/L, P <0.01, respectively). Elevated levels of N-ANP and N-BNP predicted mortality after stroke (risk ratio [RR] 4.3, P <0.01 and RR 3.9, P <0.01, respectively) and after AMI ( P <0.05), and remained independent predictors of death after stroke even after adjustment for age, diabetes, coronary artery disease, and medication (RR 3.9, P <0.05 and RR 3.7, P <0.05, respectively).

Conclusion— Plasma levels of natriuretic peptides are elevated in the acute phase of stroke and predict poststroke mortality.

Circadian variations of plasma renin activity (PRA), aldosterone and electrolyte concentrations in plasma in pregnant and non-pregnant goats

The aim of this study was to estimate and analyse circadian variations of the renin-angiotensin-aldosterone system (RAA) activity in blood of goats and the influence of late pregnancy on the circadian variations of RAA system. The study was carried out on a group of 17 non-pregnant and 9 pregnant goats. The animals were kept in uniform environmental conditions, (9 h light/15 h darkness). Blood samples were collected seven times over a period of 24 h, every 4 h. Plasma renin activity (PRA), plasma aldosterone (PA), sodium, potassium and chloride concentrations were determined. PRA and PA of both groups changed during 24 h, with the highest values in the dark phase and with higher RAA system activity (especially during the night) in the pregnant goats. In the non-pregnant goats, no circadian changes in PRA and PA were observed. The circadian changes in PRA and PA found in pregnant goats had acrophases at 06:27 h and 01:13 h, respectively. Plasma electrolyte concentrations in both groups of goats also changed during 24 h. These results suggest that circadian changes of potassium concentration in plasma of goats during late pregnancy may be one of the main factors affecting the RAA system.