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

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 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

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

The effect of intranasal nifedipine drops in 20 randomly chosen patients with diethyl-ether induced hypertension by inhalation anesthesia was observed. Patients were placed in two groups: the first group received intranasal nifedipine at the time of induction and the second group received intranasal nifedipine at the time to skin incision. The change in mean arterial pressure in the first group was not significant, but in the second group, the increase in mean arterial pressure was significant immediately after intranasal administration of nifedipine at the time of skin incision. An increase in pulse rate was noted with the increase in mean arterial pressure and this is thought to result from the stimulation of catecholamine secretion and baroreceptor reflex. Since the difference in mean arterial pressure between the two groups was minimal at ten minutes and twenty minutes after skin incision, it is suggested that the onset of intranasal nifedipine is quite fast. Based on the authors' experience, intranasal administration of nifedipine is very useful in preventing or treating hypertension during inhalation anesthesia using diethyl-ether.
Administration, Intranasal* ; Anesthesia, Inhalation ; Arterial Pressure ; Baroreflex ; Ether* ; Heart Rate ; Humans ; Hypertension ; Nifedipine* ; Skin

BACKGROUND: The arterial baroreflex is a key mechanism involved in blood pressure (BP) homeostasis and serves as a pressure buffer system against increase and decrease in BP. In contrast to awake patients, little has been known about correlations among METHODS assessing spontaneous baroreflex sensitivity (SBRS) during general anesthesia. The aim of present study was to compare SBRS obtained from sequence method and transfer function analysis (TFA), and examined their relationship to vagal cardiac function in patients during sevoflurane general anesthesia. METHODS: 20 patients were anesthetized with 1 MAC sevoflurane with 50% N2O and mechanically ventilated at 0.25 Hz. 5 min beat-to-beat BP and electrocardiogram were recorded to assess sequence BRS and TFA BRS from spontaneous RR interval and systolic BP fluctuation. We derived 4 proposed indices (Sequence BRS, low frequency (LF) BRS, high frequency (HF) BRS, and average BRS). RESULTS: The indices were correlated with each other significantly and the Bland-Altman method demonstrated that sequence BRS was in close agreement with each other except LF BRS. The indices were also correlated highly with HF heart rate variability representing vagal cardiac function. CONCLUSIONS: SBRS was related to vagal cardic function. Because of the correlations and agreements between these two METHODS, it may employ them except for LF BRS during sevoflurane general anesthesia.
Anesthesia* ; Anesthesia, General ; Baroreflex* ; Blood Pressure ; Electrocardiography ; Heart Rate ; Homeostasis ; Humans

The autonomic nervous system (ANS) contributes importantly to the short-term regulation of blood pressure and cardiovascular variability. Evidence from numerous studies indicates a strong association among compromised ANS, sudden cardiac death, blood pressure instability and adverse postoperative cardiac events. Heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity (BRS) have been studied for years as tools for assessing ANS. In this review, physiological origin and measurement principle of cardiovascular fluctuations are described and changes in indices of HRV, BPV and BRS observed in various situations of anesthesia are discussed. Anesthesiologists need to consider estimation of ANS function to predict hypertension/hypotension after anesthesia induction and to improve short-term outcome and long-term cardiac morbidity and mortality.
Anesthesia ; Anesthesiology ; Autonomic Nervous System ; Baroreflex ; Blood Pressure ; Death, Sudden, Cardiac ; Heart ; Heart Rate

BACKGROUND: It is reported that ketamine increases central sympathetic activity as well as catecholamine reuptake inhibition. However, little has been known about baroreflex control of heart rate in ketamine anesthetized humans. Thus, the aim of this study was to analyze the effect of ketamine on spontaneous baroreflex sensitivity (BRS) during ketamine induction of anesthesia. METHODS: Beat-by-beat arterial blood pressure and electrocardiogram at 5 min before and 10 min after ketamine administration (2 mg/kg) were recorded in twenty healthy living liver transplant donors. Spontaneous BRS was assessed by sequence method and transfer function analysis method. RESULTS: Spontaneous BRS assessed by sequence method, BRSsequence, decreased from 13.7 +/- 6.3 to 7.8 +/- 4.5 ms/mmHg (P < 0.001). Spontaneous BRS assessed by low frequency transfer function method decreased from 10.9 +/- 5.4 to 7.0 +/- 4.1 ms/mmHg and by high frequency transfer function method from 14.8 +/- 9.2 to 8.7 +/- 8.8 ms/mmHg, respectively (P < 0.05). 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 ; Arterial Pressure ; Baroreflex* ; Electrocardiography ; Heart Rate* ; Heart* ; Hemodynamics ; Humans ; Ketamine* ; Liver ; Tissue Donors