scholarly journals Carotid and aortic baroreflexes of the rat: I. Open-loop steady-state properties and blood pressure variability

2000 ◽  
Vol 279 (5) ◽  
pp. R1910-R1921 ◽  
Author(s):  
Barry R. Dworkin ◽  
Susan Dworkin ◽  
Xiaorui Tang
Keyword(s):  
Blood Pressure ◽  
Venous Pressure ◽  
Open Loop ◽  
Direct Stimulation ◽  
Large Variability ◽  
Aortic Depressor Nerve ◽  
Cardiac Responses ◽  
C Fibers ◽  
Stimulus Mode ◽  
Sinus Pressure

To characterize the baroreflex in central nervous system-intact neuromuscular-blocked rats, we measured the vascular and cardiac responses and compared direct stimulation of the aortic depressor nerve (ADN) with a capacitance electrode (differentially activating either A or A + C fibers) to carotid sinus pressure with a micro-balloon (SINUS). One-thousand-two-hundred-ninety-seven open-loop measurements of systolic blood pressure (SBP), heart rate, venous pressure (VBP), and mesenteric (msBF), femoral (fmBF), and skin (skBF) blood flow were completed; the linear range of the effects was determined for each response and stimulus mode. The rats were sinoaortic denervated (SAD). The open-loop stimulation effect was very stable; e.g., the mean effect of 790 ADN stimulations during >7 days was −9.8 mmHg, with an average drift of +0.001 mmHg/h. In contrast, there was large variability of the SBP baseline (e.g., SD = ±10.9), which was due to SAD (±6.3 to ±16.3 mmHg, t = −13.9, df = 4, P < 0.0002) and was reversed by ganglionic block (±10.8 to ± 2.9 mmHg, t = −12.9, df = 3, P < 0.001). The ADN stimuli produced larger depressor responses than sinus stimuli (−66 vs. −45 mmHg); all component responses paralleled the magnitude of the SBP effect, except interbeat interval (IBI), for which the ADN ΔIBI was ≈10 times that of SINUS. For all stimuli, fmBF increased and msBF did not. Mesenteric and femoral vascular conductance both increased, whereas VBP decreased and skBF followed SBP. We found that for all baroreflex response components, with the exception of SINUS-elicited ΔIBI, there was an orderly, substantially linear, relationship between stimulus strength and response magnitude.

scholarly journals Carotid and aortic baroreflexes of the rat: II. Open-loop frequency response and the blood pressure spectrum

2000 ◽  
Vol 279 (5) ◽  
pp. R1922-R1933 ◽  
Author(s):  
Barry R. Dworkin ◽  
Xiaorui Tang ◽  
Alan J. Snyder ◽  
Susan Dworkin
Keyword(s):  
Blood Pressure ◽  
Venous Pressure ◽  
Low Frequency ◽  
Noise Spectrum ◽  
Open Loop ◽  
Step Response ◽  
Algebraic Solution ◽  
Noise Power ◽  
Vascular Conductance ◽  
Aortic Depressor Nerve

To determine the relationship between blood pressure (BP) variability and the open-loop frequency domain transfer function (TF) of the baroreflexes, we measured the pre- and postsinoaortic denervation (SAD) spectra and the effects of periodic and step inputs to the aortic depressor nerve and isolated carotid sinus of central nervous system-intact, neuromuscular-blocked (NMB) rats. Similar to previous results in freely moving rats, SAD greatly increased very low frequency (VLF) (0.01–0.2 Hz) systolic blood pressure (SBP) noise power. Step response-frequency measurements for SBP; interbeat interval (IBI); venous pressure; mesenteric, femoral, and skin blood flow; and direct modulation analyses of SBP showed that only VLF variability could be substantially attenuated by an intact baroreflex. The −3-dB frequency for SBP is 0.035–0.056 Hz; femoral vascular conductance is similar to SBP, but mesenteric vascular conductance has a reliably lower and IBI has a reliably higher −3-dB point. The overall open-loop transportation lag, of which ≤0.1 s is neural, is ≈1.07 s. Constrained algebraic solution, over a range of frequencies, of the pre- and postSAD endogenous noise spectra and the independently determined relative frequency and absolute lag measurements was used to calculate the absolute gain for the open-loop TF. The average gain at 0.02 Hz, the frequency of maximum sensitivity, was 1.47 (95% confidence interval = ±0.48), which agrees well with estimates for the dog reversible sinus. We found that, in the NMB rat, the effects of SAD on the BP noise spectrum were accounted for by the open-loop properties of the baroreflex.

Splenic afferents and some of their reflex responses

1982 ◽  
Vol 242 (3) ◽  
pp. R247-R254 ◽  
Author(s):  
N. L. Herman ◽  
D. R. Kostreva ◽  
J. P. Kampine
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Venous Pressure ◽  
Systemic Blood Pressure ◽  
Contractile Force ◽  
Afferent Nerve ◽  
Nerve Activity ◽  
Efferent Nerve ◽  
C Fibers ◽  
Stimulation Period

Afferent nerve activity was recorded from the distal ends of cut splenic nerves in pentobarbital- (35 mg/kg) anesthetized mongrel dogs (15-20 kg). Increases in splenic venous pressure (SVP) produced either by manual compression of discrete portions of the spleen or splenic contraction produced by injection of epinephrine (100 micrograms) into the splenic artery or vein of an occluded spleen produced significant increases in SVP and splenic afferent nerve activity. Increases in splenic afferent nerve activity were linearly related to increases in SVP. Histological sections of nerves from which afferent recordings were obtained demonstrated that all afferents were unmyelinated C-fibers. Electrical stimulation of the cut central end of splenic nerves resulted in marked reflex increases in both renal and cardiopulmonary sympathetic efferent nerve activity that remained elevated throughout the stimulation period. Reflex increase in cardiopulmonary sympathetic efferent nerve activity was associated with increases in right (22-45%) and left (11-19%) ventricular contractile force measured with Brodie-Walton strain gauge transducers, in heart rate (5-15 beats/min), and in blood pressure (5-10 mmHg). This study is the first to demonstrate both the existence of low-pressure baroreceptors in the spleen and that these splenic afferents can reflexly alter cardiopulmonary and renal sympathetic efferent nerve activity, heart rate, ventricular contractile force, and systemic blood pressure.

Effect of fluid bolus triggers and their combination on fluid responsiveness in optimization phase of severe sepsis and septic shock resuscitation

MedPharmRes ◽  
2018 ◽  
Vol 2 (3) ◽  
pp. 27-32
Author(s):  
Bien Le ◽  
Dai Huynh ◽  
Mai Tuan ◽  
Minh Phan ◽  
Thao Pham ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Septic Shock ◽  
Severe Sepsis ◽  
Fluid Responsiveness ◽  
Statistical Significance ◽  
Venous Pressure ◽  
Fluid Bolus ◽  
Low Blood Pressure ◽  
Low Central Venous Pressure ◽  
Sepsis And Septic Shock

Objectives: to evaluate the fluid responsiveness according to fluid bolus triggers and their combination in severe sepsis and septic shock. Design: observational study. Patients and Methods: patients with severe sepsis and septic shock who already received fluid after rescue phase of resuscitation. Fluid bolus (FB) was prescribed upon perceived hypovolemic manifestations: low central venous pressure (CVP), low blood pressure, tachycardia, low urine output (UOP), hyperlactatemia. FB was performed by Ringer lactate 500 ml/30 min and responsiveness was defined by increasing in stroke volume (SV) ≥15%. Results: 84 patients were enrolled, among them 30 responded to FB (35.7%). Demographic and hemodynamic profile before fluid bolus were similar between responders and non-responders, except CVP was lower in responders (7.3 ± 3.4 mmHg vs 9.2 ± 3.6 mmHg) (p 0.018). Fluid response in low CVP, low blood pressure, tachycardia, low UOP, hyperlactatemia were 48.6%, 47.4%, 38.5%, 37.0%, 36.8% making the odd ratio (OR) of these triggers were 2.81 (1.09-7.27), 1.60 (0.54-4.78), 1.89 (0.58-6.18), 1.15 (0.41-3.27) and 1.27 (0.46-3.53) respectively. Although CVP < 8 mmHg had a higher response rate, the association was not consistent at lower cut-offs. The combination of these triggers appeared to raise fluid response but did not reach statistical significance: 26.7% (1 trigger), 31.0% (2 triggers), 35.7% (3 triggers), 55.6% (4 triggers), 100% (5 triggers). Conclusions: fluid responsiveness was low in optimization phase of resuscitation. No fluid bolus trigger was superior to the others in term of providing a higher responsiveness, their combination did not improve fluid responsiveness as well.

Abstract 12689: Cardiovascular Responses to Energy Drinks in a Healthy Population: The C-energy Study

Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Teri M Kozik ◽  
Mouchumi Bhattacharyya ◽  
Teresa T Nguyen ◽  
Therese F Connolly ◽  
Walther Chien ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Systolic Blood Pressure ◽  
Vital Signs ◽  
Cardiovascular Responses ◽  
Energy Drinks ◽  
Energy Drink ◽  
Emergency Department Visits ◽  
Qtc Interval ◽  
Cardiac Responses ◽  
Energy Drink Consumption

Introduction: Energy drinks are presumed to enhance energy, physical endurance, mood, and boost metabolism. Serious health risks have been reported with energy drink consumption such as myocardial infarction, cardiac arrest, stroke, seizures, and arrhythmias. More than 20,000 emergency department visits related to energy drink consumption were reported in 2011. Little is known about the possible pathophysiological mechanisms and adverse events associated with energy drinks. Unlike the tobacco and alcohol industry, there are limited restrictions regulating the purchasing and marketing of these drinks. Purpose: To determine if consumption of energy drinks alter; vital signs (blood pressure, temperature), electrolytes (magnesium, potassium, calcium), activated bleeding time (ACT), or cardiac responses measured with a 12-lead electrocardiographic (ECG) Holter. Method: Subjects consumed two-16 ounce cans of an energy drink within one hour and remained in the lab where data was collected at base line (BL) and then during four hours post consumption (PC). Vital signs were taken every 30 minutes; blood samples were collected at BL, one, two and four hours PC and ECG data was collected throughout the entire study period. Paired students t-test and a corresponding non-parametric test (Wilcoxon signed rank) were used for analysis of the data. Results: Fourteen healthy young subjects were recruited (mean age 28.6 years). Systolic blood pressure (BL=132, ±7.83; PC= 151, ±11.21; p=.001); QTc interval (BL=423, ±22.74; PC=503, ±24.56; p<.001); magnesium level (BL 2.04, ± 0.09; PC=2.13, ±0.15; p=.05); and calcium level (BL=9.31, ±.28; PC=9.52, ±.22; p=.018) significantly increased from BL. While potassium and ACT fluctuated (increase and decrease) no significant changes were observed. Eight of the fourteen subjects (57%) developed a QTc >500 milliseconds PC. Conclusions: In our sample, consumption of energy drinks increased systolic blood pressure, serum magnesium and calcium, and resulted in repolarization abnormalities. Because these physiological responses can lead to arrhythmias and other abnormal cardiac responses, further study in a larger sample is needed to determine the effects and possible consequences of energy drink consumption.

Acute effects of caffeine ingestion at rest in humans with impaired epinephrine responses

1996 ◽  
Vol 80 (3) ◽  
pp. 999-1005 ◽  
Author(s):  
M. Van Soeren ◽  
T. Mohr ◽  
M. Kjaer ◽  
T. E. Graham
Keyword(s):  
Blood Pressure ◽  
Adenosine Receptors ◽  
Vascular Tissue ◽  
Physiological Responses ◽  
Acute Effects ◽  
Peripheral Vascular ◽  
Direct Stimulation ◽  
Spinal Cord Lesions ◽  
Caffeine Ingestion ◽  
Stimulation Of

Caffeine ingestion has been demonstrated to increase circulating epinephrine (Epi) and norepinephrine (NE), elevate free fatty acids (FFAs), and alter heart rate, blood pressure (BP), and ventilation in humans. Whether these physiological responses are a result of caffeine acting through direct stimulation of specific tissues via adenosine receptors or secondary to Epi increases is not known. In the present experiment, six tetraplegics (level of spinal cord lesions C4-C6) were tested at rest for 3 h to investigate the effects of 6 mg/kg caffeine in capsule form on subjects with impaired Epi responses. Ventilatory, cardiovascular, metabolic, and hormonal data were collected every 15-20 min after caffeine ingestion. There were no significant (P > 0.05) increases in plasma Epi after caffeine ingestion [0.19 +/- 0.04 (SE) nM (preingestion); 0.20 +/- 0.04 nM (80 min postingestion)] or in plasma NE [0.53 +/- 0.16 nM (preingestion); 0.49 +/- 0.09 nM (80 min postingestion; P > 0.05)]. However, significant increases were found in serum FFAs [0.53 +/- 0.08 nM (preingestion); 1.03 +/- 0.20 mM (40 min postingestion; P < 0.05] and in glycerol. These concentrations remained elevated throughout the experiment. BP increased in the first hour postingestion. These data demonstrate that caffeine in physiological doses directly stimulates specific tissues, i.e., adipose and peripheral vascular tissue, and these effects are not secondary to increases in Epi after caffeine ingestion.

Characterization of baroreflex impairment in conscious dogs with pacing-induced heart failure

1993 ◽  
Vol 265 (5) ◽  
pp. R1132-R1140 ◽  
Author(s):  
N. B. Olivier ◽  
R. B. Stephenson
Keyword(s):  
Heart Failure ◽  
Blood Pressure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Peripheral Resistance ◽  
Open Loop ◽  
Ventricular Pacing ◽  
Baroreflex Control ◽  
Rapid Ventricular Pacing ◽  
Reflex Control

Open-loop baroreflex responses were evaluated in eight conscious dogs before and during congestive heart failure to determine the effects of failure on baroreflex control of blood pressure, heart rate, cardiac output, and total peripheral resistance. Heart failure was induced by rapid ventricular pacing. Baroreflex function was determined by calculation of the range and gain of the open-loop stimulus-response relationships for the effect of carotid sinus pressure on blood pressure, heart rate, cardiac output, and total peripheral resistance. The range and gain of blood pressure responses were substantially reduced as early as 3 days after induction of heart failure (161 +/- 6 to 99 +/- 8 mmHg and -2.7 +/- 0.3 to -1.5 +/- 0.1, respectively) and remained depressed for the 21 days of heart failure. This depression in baroreflex control of blood pressure was associated with similar depressions in reflex range and gain for heart rate (125 +/- 9 to 78 +/- 11 beats/min and -2.05 +/- 0.2 to -1.16 +/- 0.2 beats/min, respectively) and cardiac output (1.74 +/- 0.2 to 0.46 +/- 0.2 l/min and -0.81 +/- 0.02 to -0.027 +/- 0.008 l/min, respectively). The group-averaged range and gain for reflex control of vascular resistance were not altered by heart failure. In three dogs, discontinuation of rapid ventricular pacing led to resolution of heart failure within 7 days and partial restoration of the range and gain of reflex control of blood pressure. We conclude that heart failure reversibly depresses baroreflex control of blood pressure principally through a concurrent reduction in reflex control of cardiac output, whereas reflex control of vascular resistance is not consistently affected.

scholarly journals Hemodynamic Monitoring During Heated Intraoperative Intraperitoneal Chemotherapy Using the FloTrac/Vigileo System

2015 ◽  
Vol 100 (6) ◽  
pp. 1033-1039 ◽  
Author(s):  
Christos Mavroudis ◽  
Leonidas Alevizos ◽  
Konstantinos M. Stamou ◽  
Theodosia Vogiatzaki ◽  
Savvas Eleftheriadis ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Intraperitoneal Chemotherapy ◽  
Cytoreductive Surgery ◽  
Peritoneal Cancer Index ◽  
Venous Pressure ◽  
Term Survival ◽  
Continuous Increase ◽  
Peritoneal Cancer ◽  
American Society ◽  
American Society Of Anesthesiologists

Cytoreductive surgery with HIPEC has provided a chance for long-term survival in selected patients. However, perioperative management remains a challenge for the anesthesiology team. The aim of this study was to evaluate the changes in hemodynamic parameters during hyperthermic intraperitoneal chemotherapy (HIPEC) using the FloTrac/Vigileo system. Forty-one consecutive patients undergoing cytoreductive surgery and HIPEC were enrolled. Heart rate (HR), esophageal temperature, and cardiac output (CO) steadily increased until the end of HIPEC. In the first half of HIPEC, systolic blood pressure (SBP) and central venous pressure (CVP) increased whereas systemic vascular resistance (SVR) decreased; SVR stabilized in the second half. Diastolic blood pressure (DBP), mean arterial pressure (MAP), and stroke volume (SV) showed no significant variation. Male gender was related to increased CVP, CO, and SV, and decreased SVR; age &gt;55 years was related to increased SBP, and peritoneal cancer index (PCI) was correlated with HR, DBP, and SV. PCI &gt;14 was associated with increased HR and decreased DBP and MAP. American Society of Anesthesiologists score &gt;1 was related to decreased CO and SV. Patients undergoing HIPEC develop a hyperdynamic circulatory state because of the increased temperature, characterized by a steady decrease in SVR and continuous increase in HR and CO. FloTrac/Vigileo system may provide an easy-to-handle, noninvasive monitoring tool.

The Generation of Kinins in the Blood of Dogs during Hypotension Due to Haemorrhage

1970 ◽  
Vol 39 (3) ◽  
pp. 349-365 ◽  
Author(s):  
H. E. Berry ◽  
J. G. Collier ◽  
J. R. Vane
Keyword(s):  
Blood Pressure ◽  
Time Course ◽  
Venous Pressure ◽  
Venous Blood ◽  
Systemic Circulation ◽  
Substantial Effect ◽  
Mixed Venous Blood ◽  
Shed Blood ◽  
Arterial Blood ◽  
Organ Technique

1. Circulating kinins were detected and continuously assayed during hypotension due to haemorrhage in dogs, using the blood-bathed organ technique and isolated strips of cat jejunum as the assay tissue. 2. In arterial blood kinin concentrations of 1–5 ng/ml were attained after a hypotension of 35–65 mmHg had been maintained for 10–190 min. When portal venous blood was simultaneously assayed kinins appeared earlier and in concentrations 1–2 ng/ml higher than in arterial blood. No differences in time course of kinin generation or in concentration were found when mixed venous blood and arterial blood were compared. In those instances in which the blood pressure was restored to normal by returning the shed blood, kinin formation stopped. 3. Kinin generation was due to the presence in the circulation of a kinin-forming enzyme, such as kallikrein. When kallikrein was infused into the portal vein, it was partially inactivated by the liver. 4. Prolonged intravenous infusions of kallikrein (20–60 mu kg−1 min−1) generated kinins in the circulation in concentrations (1–5 ng/ml) which were well maintained throughout the infusion, demonstrating that kinin generation is not limited by depletion of the precursor kininogen; nevertheless, the effects of kallikrein infusions on the blood pressure and central venous pressure waned. 5. It is concluded that in hypotension due to haemorrhage, an active kallikrein appears in the portal circulation. Delay in the appearance of kallikrein in the systemic circulation may be due to the kallikrein inactivating mechanism of the liver. This inactivating mechanism may fail during shock. Kinins are generated in amounts sufficient to have a substantial effect on the circulation and an influence on the course of events in shock.

Vasomotor waves of arterial blood pressure after cessation of cardiopulmonary bypass in man

Perfusion ◽  
1990 ◽  
Vol 5 (4) ◽  
pp. 261-266
Author(s):  
V. Vainionpää ◽  
A. Hollme'n ◽  
J. Timisjärvi
Keyword(s):  
Blood Pressure ◽  
Cardiopulmonary Bypass ◽  
Arterial Pressure ◽  
Venous Pressure ◽  
Systemic Arterial Pressure ◽  
Heart Patients ◽  
Arterial Blood ◽  
Pulmonary Arterial ◽  
The Mean ◽  
Epicardial Pacing

The occurrence of vasomotor waves during cardiopulmonary bypass (CPB) is a recognized phenomenon. The lesser known oscillation of arterial pressure after cessation of CPB was observed in 18 open-heart patients. The duration of an oscillatory wave was 13.5±5.0 seconds, the amplitude 6.1 ±2.6mmNg and the mean arterial pressure 76.5± 10.7mmHg. Inter-and also intraindividual variations in frequency and amplitude of the oscillation, however, did occur. In 13 patients, this oscillation occurred during ventricular epicardial pacing. The oscillation continued until the end of the operation in eight patients; in others, the oscillation was of shorter duration. An oscillation of pulmonary arterial pressure (PAP) was simultaneously observed in nine patients (eight with pacemaker) and central venous pressure (CVP) oscillation in eight patients (all with pacemaker). The duration of a wave was the same as in systemic arterial pressure and the amplitudes were 1.5-3.0mmHg in PAP and 1.0-2.0mmHg in CVP. These arterial vasomotor waves, seen here after CPB, largely resemble those observed during perfusion in man and also the Mayerwaves explored in experimental animals. The pacing rhythm seems to favourthe appearance of those blood pressure oscillations.

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