Carotid Body Tumor ; surgery ; Humans ; Hypertension ; Pressoreceptors

Hemodynamic depression (hypotension and bradycardia) can occur during or after carotid angioplasty and stenting (CAS) due to stretching of the baroreceptors in the carotid sinus. The predisposing factors of hemodynamic depression have not been reported previously. In general, hemodynamic depression after CAS may continue for up to 3-5 days, but disappears within 7 days. We report herein a 65-year-old man with severe hemodynamic depression after sequential CAS, and discuss the possible causes from an anatomical point of view.
Aged ; Angioplasty ; Carotid Sinus ; Depression ; Hemodynamics ; Humans ; Pressoreceptors ; Stents

Graded infusion and bolus injection methods of vasoactive drugs have both been used to measure baroreflex sensitivity. To determine whether the two methods produce the same values of baroreceptor sensitivity, phenylephrine and nitroglycerin was administered intravenously by both graded infusion and bolus injection methods to 11 rabbits. To evaluate the baroreflex control of heart rate(HR), a logistic sigmoid function model was used. The range of HR and baroreflex gain by the bolus method(100.53+/-0.62, 0.113+/-0.011) were significantly(p<0.05) larger than those measured by the graded infusion method(108.49+/-1.66, 0.126+/-0.013). However, there were no significant changes in the pressure at the midrange of the baroreflex curve. Thus my results indicate that baroreflex control of HR by the graded infusion and bolus injection methods is not equivalent and that baroreflex-induced HR response to a gradual change in pressure is less than that seen with a repid change.
Baroreflex* ; Colon, Sigmoid ; Heart ; Heart Rate ; Nitroglycerin ; Phenylephrine ; Pressoreceptors ; Rabbits*

OBJECTIVE: The electric analog circuit model can be used to analyse the various function of the cardio vascular system and the dynamic characteristics on each part of human body. According to the previous studies, viscous resistance, flow inertia, and vascular compliance in the cardiovascular system are analogous to resistance, inductance, and capacitance in electric circuit, so the cardiovascular system models have been represented by the electric circuit models. These approaches were to propose suitable models for the interested part of body and to simulate the various characteristics on the cardiovascular system. METHODS: This paper tried to put the characteristics of morphologic structure into the suggested electric circuit model. After setting parameter values of the model the dynamic characteristics of the cardio vascular system is simulated using VisSim, which is one of the simulation tools. RESULTS: The derived simulation results have represented major cardiovascular functions of normal adults. Also simulation results reflect the variation due to the pathophysiological state. CONCLUSION: The controller by baroreceptor, which is one of controllers to control the cardiovascular system, is appended in the model. The dynamic response characteristics and the procedure to restore blood pressure to normal state was observed by simulation lasted a certain period of bleeding.
Adult ; Blood Pressure ; Cardiovascular System* ; Compliance ; Hemorrhage ; Human Body ; Humans ; Pressoreceptors

OBJECTIVETo observe the regulation of heart rate to cardiac pump function in the phase of negative force-frequency relationship and their possible mechanisms.

METHODSThe left ventricular pressure, aortic pressure, and cardiac output were measured in isolated working heart of rat from 240 to 300 beats/min of pacing rate.

RESULTSCardiac output of isolated working heart was decreased by a proximally 20% (P < 0.01) with the increase in the pacing rate from 240 to 300 beats/min. Left ventricular end-systolic pressure (LVESP) was declined by 4.8% (P < 0.05), but left ventricular end-diastolic pressure (LVEDP) was elevated by 139% (P < 0.01) with an increase in the pacing rate. Left atrium was enlarged at 300 beats/min of pacing rate. The time from peak to 75% relaxation in left ventricular pressure was shortened with the increased pacing rate. Pressure at aortic valve close was raised (P < 0.01) and ejection duration was shortened with the increased pacing rate (P < 0.01).

CONCLUSIONThose above results suggest that there are different mechanisms between the depressed cardiac output at higher heart rate and negative force-frequency relationship. The frequency-dependent acceleration of relaxation facilitates the decline of left ventricular pressure, and then may elevate the pressure of aortic valve close in the condition that the shape of aortic pressure curve stays the same. Therefore, the ejection duration is shortened at higher pacing rate. The shortened ejection duration may induce a decrease in stroke volume of the left ventricle. The increment of heart rate is not enough to compensate the decreased stroke volume. Finally, cardiac output shows a decrease at higher heart rate.

Animals ; Blood Pressure ; Cardiac Output ; Heart Rate ; physiology ; Male ; Pressoreceptors ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo develop a system for automatically controlling carotid sinus pressure in the study on baroreceptors.

METHODSThe preparation containing carotid sinus with parts of the connected vessels and carotid sinus nerve (CS-CSN) were isolated and perfused. A critical pressure controlling component (PRE-U, Hoerbiger, Deutschland) dictated by a computer was integrated into the system to clamp the intrasinus pressure. The pressure command and the relevant intrasinus pressure were compared to evaluate the validity of the pressure controlling system.

RESULTSA variety of sinus pressure-controlling patterns, including pulsation, ramp and step pressures, could be achieved accurately by using the system, and the pressure-dependent discharge activities of sinus nerve were confirmed.

CONCLUSIONThis system for clamping carotid sinus pressure could realize multiple pressure-controlling patterns and is a useful and flexible pressure controlling method that could applied in the study on mechano-electric transduction of baroreceptors.

Animals ; Blood Pressure ; Carotid Sinus ; innervation ; physiology ; Nerve Fibers ; physiology ; Pressoreceptors ; physiology ; Rabbits

This study was Uesigned to evaluate the reflexive heart rate response to acute blood loss during sodium nitroprusside and prostaglandin E1 induced-hypotension in isoflurane anesthetized dogs. The results were as follows: 1) Reflexive increase in heart rate during induced hypotension was significantly greater in sodium nitroprusside than prostaglandin E1. 2) Reflexive increase in heart rate during induced hypotension was significantly greater prostaglandin E1 induced-hypotension than during that wih sodium nitroprusside. From these results, it suggest that prostaglandin E1 induced-hypotension provides a safer margin than with sodium nitroprusside when rapid bleeding occurs during anesthesia and surgery.
Alprostadil ; Anesthesia ; Animals ; Baroreflex* ; Dogs ; Heart Rate ; Hemorrhage ; Hypotension* ; Isoflurane ; Nitroprusside* ; Pressoreceptors* ; Reflex ; Sodium*

This study was Uesigned to evaluate the reflexive heart rate response to acute blood loss during sodium nitroprusside and prostaglandin E1 induced-hypotension in isoflurane anesthetized dogs. The results were as follows: 1) Reflexive increase in heart rate during induced hypotension was significantly greater in sodium nitroprusside than prostaglandin E1. 2) Reflexive increase in heart rate during induced hypotension was significantly greater prostaglandin E1 induced-hypotension than during that wih sodium nitroprusside. From these results, it suggest that prostaglandin E1 induced-hypotension provides a safer margin than with sodium nitroprusside when rapid bleeding occurs during anesthesia and surgery.
Alprostadil ; Anesthesia ; Animals ; Baroreflex* ; Dogs ; Heart Rate ; Hemorrhage ; Hypotension* ; Isoflurane ; Nitroprusside* ; Pressoreceptors* ; Reflex ; Sodium*

BACKGROUND AND OBJECTIVES: Central role of the vestibular system on control of blood pressure and interrelationships between the vestibular nucleus and solitary nucleus during acute hypotension were investigated in bilateral labyrinthectomized (BLX) or sinoaortic denervated (SAD) rats. Changes of electrical activity in the medial vestibular nucleus (MVN), solitary tract nucleus (STN), and rostral ventrolateral medullary nucleus (RVLM) were investigated in rats in while acute hypotension was induced by sodium nitroprusside (SNP). RESULTS: Evoked potential in MVN neuron caused by electrical stimulation of the peripheral vestibular system was composed of 3 waves with latencies of 0.48+/-.10 ms, 1.04+/-.09 ms and 1.98+/-.19 ms. Electrical stimulation to MVN or RVLM increased blood pressure. MVN at the induction of acute hypotension showed excitation in 61% of type I neurons and inhibition in 68% of type II neurons. In STN, acute hypotension produced excitation in 62.1% of neurons recorded in intact labyrinthine animals, inhibition in 72.3% of neurons recorded in BL animals, and excitation in 60% of recorded neurons in SAD animals. In RVLM, acute hypotension produced excitation in 66.7% of neurons recorded in intact labyrinthine animals and inhibition in 64.9% of neurons recorded in BL animals. In spatial distribution of STN neurons responded to acute hypotension, excitatory responses were mainly recorded in rostral and ventral portion, and inhibitory responses were mainly recorded in caudal and lateral portion. In RVLM, excitatory responses were mainly recorded in rostral and dorsomedial portion, and inhibitory responses were mainly recorded in caudal and ventrolateral portion. CONCLUSION: These results suggest that afferent signals from the peripheral vestibular receptors are transmitted to STN through the vestibular nuclei and assist to the baroreceptors for controlling blood pressure following acute hypotension.
Animals ; Blood Pressure* ; Electric Stimulation ; Evoked Potentials ; Hypotension* ; Neurons ; Nitroprusside ; Pressoreceptors ; Rats* ; Solitary Nucleus ; Vestibular Nuclei

BACKGROUND: Constriction or banding of the pulmonary artery to create pulmonary artery stenosis is a palliative procedure designed to limit pulmonary blood flow in congenital cardiac malformation with unrestricted left to right shunt. Activation of sensory endings such as the arterial baroreceptors results in an inhibitory endings in the heart. The purpose of this study is to test the hypothesis that acute pulmonary artery constriction(PAC) results in an enhanced cardiopulmonary inhibition of the arterial baroreflex. METHODS: Baroreflex control of renal sympathetic nerve activity(RSNA) were examined in rabbits before and during reversible PAC. New Zealand white rabbits were instrumented with an occluder around the main pulmonary artery, a right ventricular catheter, femoral artery and venous catheters, and recording electrodes around renal sympathetic nerves. Baroreflex mediated changes in RSNA were monitored during decreases and increases in mean arterial pressure. RESULTS: Acute PAC produced significant([<0.05) changes in mean arterial pressure(76.3+/-1.9 vs. 59.8+/-3.0mmHg), right ventricular systolic pressure(23.1+/-4.2 vs. 42.3+/-7.4mmHg), and resting RSNA(100 vs. 71+/-6.3%). The effect of acute PAC on the arterial baroreflex was characterized by decreases in RSNA range(103.0+/-1.3 vs. 83.8+/-3.8%) and gain (-3.5+/-0.2 vs. -2.6+/-0.2). CONCLUSION: Acute PAC significantly attenuates arterial baroreflex control of RSNA in rabbits. The attenuated arterial baroreflex regulation of RSNA may be result of an enhanced inhibitory influence from activated cardiac receptors.
Arterial Pressure ; Baroreflex* ; Catheters ; Constriction ; Constriction, Pathologic ; Electrodes ; Femoral Artery ; Heart ; Pressoreceptors ; Pulmonary Artery* ; Rabbits*