No abstract available.
Baroreflex* ; Cyclosporine* ; Rabbits*

Heart failure (HF) is the endstage of multiple cardiovascular diseases.Impaired autonomic regulation and sympathetic-parasympathetic imbalance are considered key factors in HF progression.Baroreflex activation therapy (BAT),a novel device-based therapy which stimulates the carotid sinuses and regulates autonomic function,has demonstrated good efficacy in treating HF and improving prognosis.This review summarized the results of the latest relevant studies to provide support for further study of BAT.
Baroreflex/physiology* ; Heart Failure/therapy* ; Humans

BACKGROUND: The sequence method of determining baroreflex sensitivity (BRSSEQ) has been reported to correlate poorly with the phenylephrine method of determining BRS in individuals with attenuated BRS. Inhalation anesthetics are also known to decrease BRS. We therefore assessed the effect of varying the systolic blood pressure (SBP) and R-R interval (RRI) thresholds on BRSSEQ values and compared these results with the BRS obtained by the modified Oxford technique (BRSMODOX). METHODS: The average number of valid sequences and BRSSEQ values were derived by varying the SBP threshold from 0.5 to 2.5 mmHg and the RRI threshold from 1 to 6 ms, and the relation of BRSSEQ values to BRSMODOX values using sequential administration of nitroprusside and phenylephrine was assessed in 40 healthy individuals during sevoflurane anesthesia. RESULTS: Increasing either the SBP thresholds or RRI thresholds resulted in a decrease in the number of valid sequences. As the SBP thresholds were decreased and the RRI thresholds were increased, BRSSEQ values increased. When the SBP threshold exceeded 1 mmHg, no significant correlations were observed between BRSSEQ and BRSMODOX values. Significant correlations between the two methods were observed for an SBP threshold of 0.5 mmHg and RRI thresholds of 1, 2, 3 and 4 ms. Biases between the two methods were 2.1, 2.1, 0.4, and 0.4 ms/mmHg for 0.5 mmHg and 1, 2, 3 and 4 ms. CONCLUSIONS: These findings suggest that adjusting the SBP threshold to 0.5 mmHg and the RRI threshold to 3 or 4 ms may improve BRSSEQ validity during sevoflurane anesthesia, when compared to BRSMODOX.
Anesthesia* ; Anesthetics, Inhalation ; Baroreflex* ; Bias (Epidemiology) ; Blood Pressure* ; Nitroprusside ; Phenylephrine

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*

BACKGROUND: The phase relationship indicates the time delay between the input signal (systolic blood pressure, SBP) and output signal (R-R interval, RRI). In contrast to the awake state, little is known about the effects of general anesthesia on the phase shift. In the present study, we tested the hypothesis that sevoflurane anesthesia causes a phase change between the two signals. METHODS: We assessed changes in phase, coherence, and baroreflex sensitivity between SBP and RRI by the use of transfer function analysis in 50 ASA 1 patients during the awake state and during end-tidal 2% sevoflurane-50% N2O anesthesia. RESULTS: SBP and RRI decreased significantly during sevoflurane anesthesia (P < 0.001). The phase in the low frequency (LF) region remained unchanged, but the phase in the high frequency (HF) region changed significantly from -29.52 +/- 50.70 to 27.28 +/- 80.22 degrees during sevoflurane anesthesia (P < 0.001). Coherence and baroreflex sensitivity between the two signals in the LF and HF regions decreased significantly during sevoflurane anesthesia (P < 0.001, respectively). CONCLUSIONS: We found that in the HF region and not in the LF region, sevoflurane anesthesia provokes the shift of the SBP-RRI phase relationship, suggesting that this change is inconsistent with a vagally mediated response.
Anesthesia* ; Anesthesia, General ; Baroreflex ; Blood Pressure* ; Heart Rate* ; Heart* ; Humans

BACKGROUND AND OBJECTIVES: Heart rate variability (HRV) illustrates the autonomic integration of the heart. Depressed HRV has been proven to be associated with an increased risk of cardiac death, whereas heart rate turbulence (HRT) is believed to reflect baroreflex sensitivity and it was recently introduced as another noninvasive tool for risk stratification. The aim of this study was to determine the relationship between the HRT and HRV parameters in Korean adults with a structurally normal heart. SUBJECTS AND METHODS: We studied 61 adults (males: 31) who showed ventricular premature complexes on 24 hour Holter recording and who were found to have normal hearts on full noninvasive investigation. We calculated the mean heart rate (RR interval), the number of VPBs, the time- and frequency-domain HRV parameters and two HRT parameters: turbulence onset (To) and turbulence slope (Ts). RESULTS: Ts showed a strong correlation with the HRV parameters (LF/HF ratio: r=0.35, p=0.006; VLF: r=0.32, p=0.013; LF: r=0.27, p=0.035; SDNN: r=0.28, p=0.029; SDANN: r=0.32, p=0.012), but To showed no significant correlation with the HRV parameters. CONCLUSION: The HRT parameters, and especially Ts, correlate strongly with the HRV parameters; therefore, Ts should be considered as a parameter that reflects the overall cardiac autonomic tone.
Adult* ; Baroreflex ; Death ; Heart Rate* ; Heart* ; Humans ; Ventricular Premature Complexes

BACKGROUND: In the previous studies, remifentanil reduces the hemodynamic change induced by endotracheal intubation. We studied the optimal effect site concentration of remifentanil for endotracheal intubation using light wand. METHODS: Sixty ASA 1 or 2 patients scheduled for elective surgery under general anesthesia were classified in three groups according to the TCI (target controlled infusion) dose of remifentanil. Each group was administered 4microgram/ml of propofol TCI, rocuronium, with 2 ng/ml (group 1), 4 ng/ml (group 2), 6 ng/ml (group 3) of remifentanil TCI. Blood pressure, heart rate and bispectral index score were measured before induction, 3 minutes after remifentanil and propofol TCI, after endotracheal intubation using light wand, and 3 minutes after endotracheal intubation. Statistical analysis was done for comparison of time and dose dependant change among the groups. RESULTS: After endotrachal intubation, blood pressure and heart rate were significantly increased in group 1, and decreased in group 2 and 3. 3 minute after endotracheal intubation, heart rate significantly decreased in group 3, but there were no changes in group 2. CONCLUSIONS: The spontaneous BRS was decreased during ketamine induction of general anesthesia. These results suggest that anesthesia induction with ketamine impairs baroreflex control of heart rate, which may provoke hemodynamic instability.
Anesthesia ; Anesthesia, General ; Baroreflex ; Blood Pressure ; Heart Rate ; Hemodynamics* ; Humans ; Intubation ; Intubation, Intratracheal* ; Ketamine ; Propofol

The hypothalamic paraventricular nucleus (PVN) is a central site for integration of the endocrine system and the autonomic nervous system. Despite a number of studies have pointed out the importance of the PVN in the central regulation of cardiovascular functions, the chemical mediators in the PVN responsible for mediating baroreflex are not well understood. In the present study, we used the conscious rats to investigate the possible involvement of glycine (Gly) in PVN in the central regulation of baroreflex induced by intravenous injection of phenylephrine (0.8 mug/0.04 mL, in 3 min). Then, the microdialysis sampling was performed in the PVN and the concentration of Gly in the microdialysate was measured by high performance liquid chromatography (HPLC) combined with electrochemical techniques, and mean arterial pressure (MAP) and heart rate (HR) were recorded simultaneously. Injection of phenylephrine elicited a significant increase (P<0.01) in MAP from the baseline of (99.5+/-14.2) mmHg to the maximum of (149.8+/-19.5) mmHg and a decrease (P<0.01) in HR from the baseline of (400.8+/-33.1) beats/min to the minimum of (273.4+/-40.8) beats/min, respectively. Synchronously, the injection of phenylephrine increased the level of Gly in the microdialysate from the PVN to (162.9+/-27.3)% of the basal level (P<0.05). Perfusion of strychnine (100 mumol/L), an antagonist of Gly receptor, into the PVN enhanced the pressor response and attenuated the bradycardic response during the baroreflex, resulting in a decrease in baroreflex sensitivity (P<0.001). Whereas, the perfusion of Gly (1 mmol/L) into the PVN did not affect the pressor response but enhanced the bradycardic response during the baroreflex, resulting in an increase in baroreflex sensitivity (P<0.001). These results suggest that endogenous Gly in the PVN may act via strychnine-sensitive Gly receptor to produce a facilitative effect on baroreflex.
Animals ; Baroreflex ; drug effects ; Glycine ; pharmacology ; Heart Rate ; Microinjections ; Paraventricular Hypothalamic Nucleus ; physiology ; Phenylephrine ; pharmacology ; Rats

The aim of the present study was to examine whether there are changes in systolic and diastolic blood pressure (SBP and DBP) and heart rate (HR) and their spectral indices in conscious free-moving rats after tail-suspension for 28 d. The tail-suspended hindlimb-unloaded (HU) rat model was used to simulate the cardiovascular effect of microgravity and the post-spaceflight cardiovascular dysfunction. The auto- and cross-spectral analysis of SBP variability (SBPV) and HR variability (HRV) were performed by the method based on the autoregressive model (AR), and the auto-spectral results was compared with the results from the classical periodogram method. The baroreceptor-heart rate reflex sensitivity (BRS) was estimated using transfer function analysis from SBP to HR. The results indicated that auto-spectral results based on the two methods were comparable, while smoother power spectral curves with distinguished peaks were trained by the AR method. The means of SBP, DBP, and HR, the main spectral indices of SBPV and HRV, and the mean average gain of transfer functions computed at low- and high-frequency ranges (0.25-0.8 Hz and 0.8-2.4 Hz) did not show significant changes before and after release from suspension. Furthermore, the main spectral indices of SBPV and HRV at different time points did not show significant differences between the control and suspension groups. However, the means of SBP, DBP, and HR at different time points were significantly higher in simulated weightless rats than those in the control rats. The findings of the present study suggest that a mid-term simulated microgravity might induce hypertension and tachycardia upon removal from the suspension which reflects a general sympathetic hyperactivity. We speculated that the sympathetic hyperactivity might be a compensatory mechanism activated in the intact animal to counteract HU-induced hypo-responsiveness of resistance vessels. In addition, lack of clear and distinct changes in HRV and BRS have also been reported in some recent space and ground-based human studies.
Animals ; Baroreflex ; Blood Pressure ; Heart Rate ; Hindlimb Suspension ; Hypertension ; Rats ; Weightlessness Simulation

BACKGROUND AND OBJECTIVES: This study was designed to examine whether the multifractal Hurst exponents of heart rate can estimate activating and deactivating spontaneous baroreflex sensitivity (SBRS). SUBJECTS AND METHODS: Age and sex matched 24 healthy volunteers were placed in the supine position and head-up tilt position for 30 minutes, and the systolic blood pressure and heart rate were measured in an noninvasive manner. When the RR interval (RRI) sequence and systolic pressure sequence simultaneously increased or decreased for more than three successive beats, the slope of the linear regression line of systolic blood pressure and RR interval sequence was defined as the value of spontaneous baroreflex sensitivity (SBRS). From the RR intervals, very short-term (alpha range, < or =12 heartbeats), short-term (beta range, > or =12 heartbeats), and the multrifractal Hurst exponents were calculated to determine the linear correlation.coefficients for SBRS. RESULTS: In the supine position, the linear correlation coefficients (p) of SBRS and H-5alpha, H-4alpha, H-3alpha, H-2alpha, H-1alpha, H1alpha, H2alpha, H3alpha, H4alpha, H5alpha were -0.195 (NS), -0.207 (NS), -0.232 (NS), -0.282 (NS), -0.355 (NS), -0.621 (0.003), -0.650 (0.001), -0.677 (0.001), -0.699 (0.0006) and -0.708 (0.0005), respectively. In the tilting position, the linear correlation coefficients of SBRS and H-5beta, H-4beta, H-3beta, H-2beta, H-1beta, H1beta, H2beta, H3beta, H4beta, H5beta were 0.024 (NS), 0.020 (NS), 0.010 (NS), -0.028 (NS), -0.193 (NS), -0.627 (0.0034), -0.607 (0.0045), -0.598 (0.0053), -0.572 (0.0084) and -0.539 (0.0141), respectively. CONCLUSION: Some of the very short-term and short-term generalized Hurst exponents, such as H5alpha and H1beta, can be used for the estimation of spontaneous baroreflex sensitivity during patient placement in the supine and head-up tilt position, respectively.
Baroreflex* ; Blood Pressure ; Healthy Volunteers ; Heart Rate* ; Heart* ; Humans ; Linear Models ; Supine Position