Baroreflex mechanisms regulating mean level of SNA differ from those regulating the timing and entrainment of the sympathetic discharges in rabbits

2006 ◽  
Vol 291 (2) ◽  
pp. R400-R409 ◽  
Author(s):  
Simon C. Malpas ◽  
Rohit Ramchandra ◽  
Sarah-Jane Guild ◽  
David M. Budgett ◽  
Carolyn J. Barrett
Keyword(s):  
Blood Pressure ◽  
Diastolic Pressure ◽  
Function Analysis ◽  
Arterial Baroreflex ◽  
Trigger Mechanism ◽  
Conscious Animal ◽  
Transfer Function Analysis ◽  
Central Tenet ◽  
The Mean ◽  
Rate Frequency

The arterial baroreflex pathway provides the fundamental basis for the short-term control of blood pressure via the rapid regulation of the mean level of sympathetic nerve activity (SNA) in response to changes in blood pressure. A central tenet in the generation and regulation of bursts of SNA is that input from the arterial baroreceptors also regulates the timing of the bursts of sympathetic activity. With the use of an implantable telemetry-based amplifier, renal SNA was recorded in intact and arterial baroreceptor-denervated (SAD) conscious rabbits. Data were collected continuously while animals were in their home cage. Mean levels of SNA were not different between SAD and baroreceptor-intact animals. Whereas SNA was unresponsive to changes in blood pressure in SAD rabbits, the timing of the bursts of SNA relative to the arterial pulse wave was maintained (time between the diastolic pressure and the next maximum SNA voltage averaged 107 ± 12 ms SAD vs. 105 ± 7 ms intact). Transfer function analysis between blood pressure and SNA indicates the average gain at the heart rate frequency was not altered by SAD, indicating strong coupling between the cardiac cycle and SNA bursts in SAD animals. Further experiments in anesthetized rabbits showed that this entrainment is lost immediately after performing baroreceptor denervation surgery and remained absent while the animal was under anesthesia but returned within 20 min of turning off the anesthesia. We propose that this finding indicates the regulation of the mean level of SNA requires the majority of input from baroreceptors to be functional; however, the regulation of the timing of the bursts in the conscious animal requires only minimal input, such as a sensitive trigger mechanism. This observation has important implications for understanding the origin and regulation of SNA.

Effect of head-down-tilt bed rest and hypovolemia on dynamic regulation of heart rate and blood pressure

2000 ◽  
Vol 279 (6) ◽  
pp. R2189-R2199 ◽  
Author(s):  
Ken-Ichi Iwasaki ◽  
Rong Zhang ◽  
Julie H. Zuckerman ◽  
James A. Pawelczyk ◽  
Benjamin D. Levine
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Transfer Function ◽  
Stroke Volume ◽  
Plasma Volume ◽  
High Frequency ◽  
Function Analysis ◽  
Bed Rest ◽  
Baroreflex Control ◽  
Transfer Function Analysis

Adaptation to head-down-tilt bed rest leads to an apparent abnormality of baroreflex regulation of cardiac period. We hypothesized that this “deconditioning response” could primarily be a result of hypovolemia, rather than a unique adaptation of the autonomic nervous system to bed rest. To test this hypothesis, nine healthy subjects underwent 2 wk of −6° head-down bed rest. One year later, five of these same subjects underwent acute hypovolemia with furosemide to produce the same reductions in plasma volume observed after bed rest. We took advantage of power spectral and transfer function analysis to examine the dynamic relationship between blood pressure (BP) and R-R interval. We found that 1) there were no significant differences between these two interventions with respect to changes in numerous cardiovascular indices, including cardiac filling pressures, arterial pressure, cardiac output, or stroke volume; 2) normalized high-frequency (0.15–0.25 Hz) power of R-R interval variability decreased significantly after both conditions, consistent with similar degrees of vagal withdrawal; 3) transfer function gain (BP to R-R interval), used as an index of arterial-cardiac baroreflex sensitivity, decreased significantly to a similar extent after both conditions in the high-frequency range; the gain also decreased similarly when expressed as BP to heart rate × stroke volume, which provides an index of the ability of the baroreflex to alter BP by modifying systemic flow; and 4) however, the low-frequency (0.05–0.15 Hz) power of systolic BP variability decreased after bed rest (−22%) compared with an increase (+155%) after acute hypovolemia, suggesting a differential response for the regulation of vascular resistance (interaction, P < 0.05). The similarity of changes in the reflex control of the circulation under both conditions is consistent with the hypothesis that reductions in plasma volume may be largely responsible for the observed changes in cardiac baroreflex control after bed rest. However, changes in vasomotor function associated with these two conditions may be different and may suggest a cardiovascular remodeling after bed rest.

Comparative β-Adrenoreceptor-Blocking Effects and Pharmacokinetics of Propranolol and Pindolol in Hypertensive Africans

1979 ◽  
Vol 57 (s5) ◽  
pp. 393s-396s ◽  
Author(s):  
L. A. Salako ◽  
A. O. Falase ◽  
A. Fadeke Aderounmu
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Systolic Blood Pressure ◽  
Diastolic Pressure ◽  
Exercise Heart Rate ◽  
Double Blind ◽  
Blocking Effects ◽  
The Mean ◽  
Exercise Induced ◽  
African Patients

1. The β-adrenoreceptor-blocking effects of pindolol were compared with those of propranolol and a placebo in a double-blind cross-over trial involving nine hypertensive African patients. 2. Heart rate, systolic blood pressure and diastolic blood pressure were measured at rest and immediately after exercise before and at intervals up to 6 h after oral administration of the drugs. In addition, plasma pindolol and propranolol concentrations were determined at the same intervals. 3. Pindolol diminished systolic blood pressure at rest and after exercise and antagonized exercise-induced tachycardia, but had no effect on resting heart rate. Propranolol diminished systolic blood pressure predominantly after exercise and reduced both resting and exercise heart rate. Both drugs had no effect on diastolic pressure. 4. The mean plasma concentration reached a peak at 2 h for each drug and this coincided with the interval at which maximal β-adrenoreceptor-blocking effect was observed.

Isradipine Therapy in Hypertensive Pediatric Patients

1997 ◽  
Vol 31 (6) ◽  
pp. 704-707 ◽  
Author(s):  
Cary E Johnson ◽  
Pamala A Jacobson ◽  
Min H Song
Keyword(s):  
Blood Pressure ◽  
Pediatric Patients ◽  
Diastolic Pressure ◽  
University Teaching ◽  
Chronic Hypertension ◽  
Pressure Measurements ◽  
Disease States ◽  
The Mean ◽  
Record Review ◽  
Retrospective Medical Record Review

OBJECTIVE: To evaluate the dosage and effectiveness of isradipine to control acute or chronic hypertension in pediatric patients. DESIGN: Retrospective medical record review. SETTING: University teaching hospital. PARTICIPANTS: Hospitalized pediatric patients aged 1 day to 16 years with hypertension treated with isradipine between January 1994 and March 1996. MEASURES: Patient age, gender, weight, disease states, current medications, isradipine dosage and formulation, pre- and postsystolic, and pre- and postdiastolic blood pressure measurements with each dose of isradipine. RESULTS: Fifty-three patients with a mean age of 5.8 ± 4.0 years were evaluated. A mean change in the blood pressure measurements taken before the first dose of isradipine compared with the values recorded after the last dose or at discharge for all patients was −11.8% ± 12.5% and −17.4% ± 19.6%, respectively, for systolic and diastolic pressure. The mean dosage of isradipine in 46 patients who received regularly scheduled doses was 0.38 ± 0.22 mg/kg/d. Patients who demonstrated a response received a mean dosage of 0.40 ± 0.20 mg/kg/d. The total daily dosage was administered in one dose for 1 patient, two doses for 15 patients, three doses for 27 patients, and four doses for 3 patients. CONCLUSIONS: Isradipine was an effective antihypertensive agent to reduce the systolic and/or diastolic blood pressure 10% or more compared with pretreatment measurements in 43 (81 %) of 53 pediatric patients. The mean dosage was 0.38 ± 0.22 mg/kg/d, most frequently administered in two or three equally divided doses, which is higher than the normal recommended dosage for adults.

scholarly journals Cerebellar Autoregulation Dynamics in Humans

2008 ◽  
Vol 28 (9) ◽  
pp. 1605-1612 ◽  
Author(s):  
Matthias Reinhard ◽  
Zora Waldkircher ◽  
Jens Timmer ◽  
Cornelius Weiller ◽  
Andreas Hetzel
Keyword(s):  
Blood Pressure ◽  
Function Analysis ◽  
Pressure Fluctuations ◽  
Posterior Inferior Cerebellar Artery ◽  
Pressure Oscillations ◽  
Cerebellar Artery ◽  
Transfer Function Analysis ◽  
Human Cerebellum ◽  
Regulatory Properties ◽  
Coefficient Method

Knowledge on autoregulation of cerebellar blood flow in humans is scarce. This study investigated whether cerebellar autoregulation dynamics and CO2 reactivity differ from those of the supratentorial circulation. In 56 healthy young adults, transcranial Doppler (TCD) monitoring of the posterior inferior cerebellar artery (PICA) and, simultaneously, of the contralateral middle cerebral artery (MCA) was performed. Autoregulation dynamics were assessed by the correlation coefficient method (indices Dx and Mx) from spontaneous blood pressure fluctuations and by transfer function analysis (phase and gain) from respiratory-induced 0.1 Hz blood pressure oscillations. CO2 reactivity was measured via inhalation of air mixed with 7% CO2. The autoregulatory indices Dx and Mx did not differ between the cerebellar (PICA) and cerebral (MCA) vasculature. Phase and gain, which describe faster aspects of autoregulation, showed slightly better values in the PICA compared with the MCA (higher phase, P = 0.005; lower gain, P = 0.007). Correlation between absolute autoregulation values in the PICA and the MCA was significant ( P < 0.001). The TCD CO2 reactivity was significantly lower in the PICA ( P < 0.001), which could be influenced by an assumed PICA dilation under hypercapnia. In conclusion, dynamic autoregulation in the human cerebellum is well operating and has slightly faster regulatory properties than the anterior cerebral circulation.

THE HEART PRELOAD AND AFTERLOAD INTERACTION AND RR INTERVALS UNDER HARD NORMOBARICHYPOXIA EXPOSURE IN HEALTHY YOUNG PERSONS

2013 ◽  
Vol 11 (3) ◽  
pp. 40-49
Author(s):  
Aleksandr Sergeyevich Radchenko ◽  
N. S. Borisenko ◽  
A. I. Kalinichenko ◽  
Yu Yu Rodionova ◽  
Yuriy Nikolayevich Korolev ◽  
...  
Keyword(s):  
Diastolic Pressure ◽  
Function Analysis ◽  
Muscle Relaxation ◽  
Left Ventricular ◽  
Smooth Muscle Relaxation ◽  
Peripheral Vascular ◽  
Oxyhemoglobin Saturation ◽  
Respiration Frequency ◽  
Transfer Function Analysis ◽  
Before And After

The study wThe left ventricular end diastolic pressure (EDP) fluctuations, specific peripheral vascular resistance (SPR) and cardiointervals (RR) on the respiration frequency under hard normobaric hypoxia (FIO2 = 0.1) were studied. 7 young men (volunteers) were subject to series of hard hypoxic exposures (6 weeks, every other day, intermittently by 6 × 5 min – FIO2 = 0.1). The hypoxic tests (HT1 and HT2) – FIO2 = 0.1, 15 min continuously) were performed before and after each series. SаO2 at the last 3 m of the tests on average was 82.5 % and 92.0 % respectively (Р < 0.05). During HT1 and HT2 (in comparison with inactivity) were increased: angle of max QRS vector (VQRS) in the frontal plain (68.5° ± 16.68 and 72.94° ± 15.32; 69.62° ± 22.4 and 74.45° ± 17.98 respectively), minutes blood flow (MBF) (6.41 ± 1.98 l/min and 6.87 ± 1.27 l/min; 5,27 ± 1,02 l/min and 5.67 ± 1.19 l/min respectively) (Р < 0.05). SPR was decreased too (27.39 ± 5.45 s.u. and 25.62 ± 4.96 s.u.; 30.59 ± 6.34 s.u. and 27.93 ± 5.77 s.u. respectively) (Р < 0.05). By means of transfer function analysis was shown that EDP fluctuations at HT2 significantly outpace by time (phase) the SPR and RR fluctuations on the respiration frequency (1.19 s ± 0.64 and 1.99 s ± 0.63 or 94.39° ± 43.3 and 125.4° ± 7.54; 1.65 s ± 1.28 and 2.22 s ± 0.87 or 101.4° ± 59.6 and 152.7° ± 21.26 respectively) (Р < 0.05). The increased oxyhemoglobin saturation is a trigger of artery wall smooth muscle relaxation mechanisms and this one is changes the background for beat to beat baroreflex realization on the respiration frequency.

scholarly journals Methodological comparison of active- and passive-driven oscillations in blood pressure; implications for the assessment of cerebral pressure-flow relationships

2015 ◽  
Vol 119 (5) ◽  
pp. 487-501 ◽  
Author(s):  
Jonathan D. Smirl ◽  
Keegan Hoffman ◽  
Yu-Chieh Tzeng ◽  
Alex Hansen ◽  
Philip N. Ainslie
Keyword(s):  
Blood Pressure ◽  
Transfer Function ◽  
Lower Body Negative Pressure ◽  
Function Analysis ◽  
Flow Dynamics ◽  
Pressure Flow ◽  
Reliable Assessment ◽  
Transfer Function Analysis ◽  
End Tidal ◽  
Normalized Gain

We examined the between-day reproducibility of active (squat-stand maneuvers)- and passive [oscillatory lower-body negative pressure (OLBNP) maneuvers]-driven oscillations in blood pressure. These relationships were examined in both younger ( n = 10; 25 ± 3 yr) and older ( n = 9; 66 ± 4 yr) adults. Each testing protocol incorporated rest (5 min), followed by driven maneuvers at 0.05 (5 min) and 0.10 (5 min) Hz to increase blood-pressure variability and improve assessment of the pressure-flow dynamics using linear transfer function analysis. Beat-to-beat blood pressure, middle cerebral artery velocity, and end-tidal partial pressure of CO2 were monitored. The pressure-flow relationship was quantified in the very low (0.02-0.07 Hz) and low (0.07–0.20 Hz) frequencies (LF; spontaneous data) and at 0.05 and 0.10 Hz (driven maneuvers point estimates). Although there were no between-age differences, very few spontaneous and OLBNP transfer function metrics met the criteria for acceptable reproducibility, as reflected in a between-day, within-subject coefficient of variation (CoV) of <20%. Combined CoV data consist of LF coherence (15.1 ± 12.2%), LF gain (15.1 ± 12.2%), and LF normalized gain (18.5 ± 10.9%); OLBNP data consist of 0.05 (12.1 ± 15.%) and 0.10 (4.7 ± 7.8%) Hz coherence. In contrast, the squat-stand maneuvers revealed that all metrics (coherence: 0.6 ± 0.5 and 0.3 ± 0.5%; gain: 17.4 ± 12.3 and 12.7 ± 11.0%; normalized gain: 16.7 ± 10.9 and 15.7 ± 11.0%; and phase: 11.6 ± 10.2 and 17.3 ± 10.8%) at 0.05 and 0.10 Hz, respectively, were considered biologically acceptable for reproducibility. These findings have important implications for the reliable assessment and interpretation of cerebral pressure-flow dynamics in humans.

scholarly journals A STUDY ON CLINICO- RADIOLOGICAL PRESENTATION OF STROKE AND ITS ASSOCIATION WITH OUTCOME

2019 ◽  
Vol 3 (6) ◽  
Author(s):  
Dr. Arindam Nag ◽  
Dr. Sourav Nag ◽  
Dr Suraj Mondal ◽  
Dr Yashpal Yadav
Keyword(s):  
Computed Tomography ◽  
Blood Pressure ◽  
Ischemic Stroke ◽  
Glasgow Coma Scale ◽  
Ct Scan ◽  
Cerebrovascular Accident ◽  
Diastolic Pressure ◽  
Modified Rankin Scale ◽  
Study Population ◽  
The Mean

BACKGROUND:  Cerebrovascular diseases include some of the most common and devastating disorders: ischemic stroke, hemorrhagic stroke, and cerebrovascular anomalies such as intracranial aneurysms and arteriovenous malformations. A stroke, or cerebrovascular accident, is defined by this abrupt onset of a neurologic deficit that is attributable to a focal vascular cause. Thus, the definition of stroke is clinical, and laboratory studies including brain imaging are used to support the diagnosis. AIMS:  1.To correlate clincoradiological findings in terms of prognosis, 2. To know different types of stroke along with its area of involvement and vascular distribution and its relation with outcome, 3. Role of CT SCAN brain as an early diagnostic modality to say clinical outcome. METHODS: This descriptive epidemiological study with a cross sectional study design is to be conducted in the department of medicine (indoor), R.G.KAR Medical College and Hospital. 1st June 2017 to 31st may 2018. 100 cases to be selected during study period based on following criteria. Detailed clinical history, clinical examinations with Radiological imaging like computed tomography of brain is done. We use scoring system like Intracerebral haemorrhage score, Glasgow coma scale, Modified rankin scale. Based on clinical examination proforma all the study population had been examined including recording of blood pressure and Glasgow coma score at the time of admission. Analysed by Modified Rankin scale till the 5th day post-hospital admission after stroke. RESULT: Among the total 100 study population 59 cases were of Infarction and 41 cases were of Haemorrhagic type of stroke. Within the 59 Cases of Infarction 39 (i.e. 66%) were male cases and 20 (i.e 34%) were female cases. Within the 41 cases of Haemorrhage 29 (i.e. 71%) were male and 12 (i.e. 29%) were female.  The mean age of the study population of Infarction cases was 55.55 years ±12.84 SD. The mean age of the study population of Haemorrhage cases was 57.48years±13.46SD. Infraction cases show increased mortality among the group having systolic blood & diastolic pressure ≥ 180 mm of Hg, ≥ 110 mm of Hg respectively. Hemorrhagic cases show increased mortality among the group having systolic blood pressure, diastolic pressure ≥ 180 mm of Hg, ≥ 110 mm of Hg respectively. CONCLUSION: Incidence of haemorrhage is much higher in India (41% as per our study). The study population between 51- 60 years is most predominant age group in both the types of stroke. Most of the infarction cases presents with unconsciousness followed by slurring of speech.  Most common presenting symptoms of Haemorrhagic stroke are unconsciousness, present at about 56% of cases. The most prominent risk factor in our study population is undetected and/or uncontrolled hypertension.  Study population with SBP ≥180 and/or DBP ≥110 mm of Hg group have increased rate of mortality from stroke. The major type of ischemic stroke in our study population is partial anterior circulation stroke (PACI) 47.4%. Most of the study population having  Infarction has developed severe disability at the end of 5 days of observation, comprising of 40.5% of the total observation. Keywords:  CVA (cerebrovascular accident), CT Scan (computed tomography), MRI (Magnetic resonance imaging), GCS Scale (Glasgow coma scale)

scholarly journals Mean Blood Pressure and Velocity for Calculation of Ventricular Systolic Work

1998 ◽  
Vol 41 (1) ◽  
pp. 27-28
Author(s):  
Milan Valach
Keyword(s):  
Blood Pressure ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Diastolic Pressure ◽  
Weighted Average ◽  
Average Pressure ◽  
Mean Pressure ◽  
The Mean ◽  
Definition Of ◽  
Ejection Phase

In physiology, the mean arterial pressure is defined as an average pressure during one or several cardiac cycles. When calculus is not used, the mean pressure is approximately calculated as the diastolic pressure plus one third of the pulse pressure. In this article it is demonstrated that, when ventricular systolic work is concerned, the above definition of mean pressure must be replaced by a weighted average during the ejection phase of the systole. This gives a formula, by which a much higher estimate of the mean pressure is obtained.

scholarly journals Trends in end digit preference for blood pressure and associations with cardiovascular outcomes in Canadian and UK primary care: a retrospective observational study

BMJ Open ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. e024970 ◽  
Author(s):  
Michelle Greiver ◽  
Sumeet Kalia ◽  
Teja Voruganti ◽  
Babak Aliarzadeh ◽  
Rahim Moineddin ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Primary Care ◽  
Observational Study ◽  
Diastolic Pressure ◽  
Cardiovascular Outcomes ◽  
Retrospective Observational Study ◽  
Digit Preference ◽  
The Mean ◽  
The Uk ◽  
Primary Care Practices

ObjectivesTo study systematic errors in recording blood pressure (BP) as measured by end digit preference (EDP); to determine associations between EDP, uptake of Automated Office BP (AOBP) machines and cardiovascular outcomes.DesignRetrospective observational study using routinely collected electronic medical record data from 2006 to 2015 and a survey on year of AOBP acquisition in Toronto, Canada in 2017.SettingPrimary care practices in Canada and the UK.ParticipantsAdults aged 18 years or more.Main outcome measuresMean rates of EDP and change in rates. Rates of EDP following acquisition of an AOBP machine. Associations between site EDP levels and mean BP. Associations between site EDP levels and frequency of cardiovascular outcomes.Results707 227 patients in Canada and 1 558 471 patients in the UK were included. From 2006 to 2015, the mean rate of BP readings with both systolic and diastolic pressure ending in zero decreased from 26.6% to 15.4% in Canada and from 24.2% to 17.3% in the UK. Systolic BP readings ending in zero decreased from 41.8% to 32.5% in the 3 years following the purchase of an AOBP machine. Sites with high EDP had a mean systolic BP of 2.0 mm Hg in Canada, and 1.7 mm Hg in the UK, lower than sites with no or low EDP. Patients in sites with high levels of EDP had a higher frequency of stroke (standardised morbidity ratio (SMR) 1.15, 95% CI 1.12 to 1.17), myocardial infarction (SMR 1.16, 95% CI 1.14 to 1.19) and angina (SMR 1.25, 95% CI 1.22 to 1.28) than patients in sites with no or low EDP.ConclusionsAcquisition of an AOBP machine was associated with a decrease in EDP levels. Sites with higher rates of EDP had lower mean BPs and a higher frequency of adverse cardiovascular outcomes. The routine use of manual office-based BP measurement should be reconsidered.

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