Assessment of the Mechanism of Arterial Blood Pressure Change during Sevoflurane Induction: Beat-to-Beat Analysis of Hemodynamic Variables Using a Modelflow Method / 대한마취과학회지

BACKGROUND: A modelflow method provides beat-to-beat analysis of cardiovascular variables based on arterial pulse pressure analysis. In this study, we assessed the mechanism of arterial blood pressure (ABP) change during sevoflurane induction by the analysis of beat-to-beat hemodynamic changes using a modelflow method. METHODS: Beat-to-beat ABP was measured during a stable conscious state (baseline) and vital capacity induction with sevoflurane 6 vol% and oxygen 8 L/min in 18 healthy living liver transplant donors. Alterations of beat-to-beat systolic ABP, mean ABP, diastolic ABP, heart rate (HR), stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR) by sevoflurane induction were estimated noninvasively using a modelflow method simulating aortic input impedance from an ABP waveform. RESULTS: After sevoflurane induction, ABP, SV, CO, and TPR decreased significantly (all P < 0.05), but HR did not change significantly. After tracheal intubation, ABP, CO, and TPR did not change significantly compared with baseline, but HR increased and SV decreased significantly (both P < 0.05). CONCLUSIONS: Using a modelflow beat-to-beat analysis of cardiovascular variables, we found that ABP did not change significantly compared to baseline after tracheal intubation during sevoflurane induction, indicating the counteraction of increased HR and decreased SV, and that the reduction of SV by tracheal intubation suggests the suppression by increased HR and TPR compared with that after sevoflurane induction.

Assessment of Cardiovascular Autonomic Function in Patients with Liver Cirrhosis Using Heart Rate Variability, Blood Pressure Variability and Baroreflex Sensitivity / 대한마취과학회지

BACKGROUND: Liver cirrhosis is associated with several hemodynamic abnormalities, including an impairment of autonomic nervous system reflexes, but very few have compared the disease severity with cardiovascular autonomic dysfunction assessed by spectral analysis of blood pressure and electrocardiogram. The aim of this study was to investigate the relationship between Child-Turcotte-Pugh (CTP) score and autonomic indices in patients with liver cirrhosis using the heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity (BRS). METHODS: Fifty patients scheduled for liver transplantation recipients under general anesthesia were enrolled in the study. Beat-to-beat blood pressure and RR interval were measured for five minutes before anesthesia induction. HRV and BPV were estimated by power spectral analysis of RR interval and systolic blood pressure. BRS was estimated by both the sequence method (Sequence BRS) and high frequency (HF) gain of transfer function analysis (HF BRS). RESULTS: Significant inverse correlations between CTP score and Sequence BRS (r = -0.61), HF BRS (r = -0.59), low frequency (LF) and HF power of HRV (r = -0.57, r = -0.46), LF power of BPV (r = -0.37) were found. However, no significant correlations were observed between CTP score and LF/HF ratio of HRV (r = -0.02) and HF power of BPV (r = 0.27). CONCLUSIONS: These results showed that autonomic dysfunction assessed by spectral analysis was associated with increasing severity of liver cirrhosis. Further study will be needed to clarify relationship between our findings and hemodynamic fluctuations during anesthesia for liver transplantation.

Influence of Anesthesia Induction with Ketamine on Baroreflex Control of Heart Rate / 대한마취과학회지

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.

Change of Blood Pressure Variability before and during Sevoflurane Anesthesia / 대한마취과학회지

BACKGROUND: Relatively little is known about the effects of general anesthesia on blood pressure variability (BPV). This study was designed to evaluate the changes of high frequency (HF) and low frequency (LF) of BPV before and during general anesthesia with sevoflurane. METHODS: Beat-to-beat blood pressure was recorded at conscious baseline and during general anesthesia at 2% end-tidal sevoflurane in 17 healthy living-liver transplantation donors. BPV estimated by power spectra of systolic (SBP) and mean blood pressure (MBP) was calculated. RESULTS: Both LF power of SBP and MBP were diminished to 96.2% and 97.1% during sevoflurane anesthesia (5.5 +/- 2.8 to 0.2 +/- 0.2 mmHg2, 6.6 +/- 3.7 to 0.2 +/- 0.2 mmHg2, P < 0.001 for both). However, there were no significant changes of HF power of SBP and MBP during sevoflurane anesthesia. CONCLUSION: Sevoflurane anesthesia reduced noticeably LF power, which was associated with sympathetic vasomotor activity, but not HF power, which represents mostly the mechanical effect of respiration on blood pressure, of BPV.

Validity of Heart Rate Variability Using Poincare Plot for Assessing Vagal Tone during General Anesthesia / 대한마취과학회지

BACKGROUND: A poincare plot of the heart rate variability (HRV) allows for the quantitative display of the vagal tone in conscious humans. However, relatively little is known about standard deviation 1 (SD1) from the poincare plot reflecting the vagal tone and correlating with the high frequency (HF) spectral power of the HRV during general anesthesia. Thus, the association of SD1 from the poincare plot was examined, along with the HF spectral power of the HRV during general anesthesia. METHODS: Beat-to-beat electrocardiograms were recorded for 5 min in 23 patients (isoflurane group, n = 13; sevoflurane group, n = 10) before, during and after general anesthesia. The low frequency (LF) and HF spectral powers, the LF/HF ratio of the HRV and the SD1 and standard deviation 2 (SD2) from the poincare plot were calculated. RESULTS: Both the HF spectral power of the HRV and SD1 from the poincare plot were reduced following general anesthesia, but recovered thereafter. The recovery of both the HF spectral power and SD1 from the poincare plot in the sevoflurane group was faster than those in the isoflurane group. There were strong correlations between the HF spectral power and SD1 before, during and after anesthesia. CONCLUSIONS: These data suggest that the SD1 from the poincare plot is a useful and valid parameter for analysis of the vagal tone during general anesthesia.

Assessment of Autonomic Response before and after Total Spinal Anesthesia in Rats: Power Spectral Analysis / 대한마취과학회지

BACKGROUND: Total spinal anesthesia (TSA) after injections of local anesthetics into the intrathecal space during epidural anesthesia is not rare. TSA anesthetizes cranial nerves and peripheral nerves, causes specific circulatory disturbances related to autonomic imbalance. Spectral analysis of heart rate variability (HRV) and blood pressure variability (BPV) provide a dynamic assessment of sympathetic and parasympathetic tone. Cross-spectral analysis has been used to emphasize this dynamic baroreflex control of HR as a frequency-dependent phenomenon and allows an assessment of baroreflex function. To examine the effects of TSA on the autonomic nervous system, we used spectral and cross-spectral analytic METHODS. METHODS: We investigated 14 rats before and after TSA. Power spectral densities of blood pressure (BP) and heart rate (HR) were estimated by fast Fourier transform. To evaluate the effect of TSA on baroreflex function, the cross spectral gain, phase, and coherence between beat-to-beat BP and HR signals were calculated by using transfer function analysis. RESULTS: With the onset of TSA, BP and HR significantly decreased. TSA significantly decreased the low frequency (LF) and high frequency (HF) components of HRV and BPV. Baroreflex sensitivity (BRS) obtained from transfer function gain between these variables was significantly decreased. CONCLUSIONS: TSA reduces the LF and HF components of HRV and BPV. These suggest that TSA in rats decreases both parasympathetic and sympathetic drive. Moreover, the decrease in BRS suggests impairment of cardiac baroreflex buffering function during TSA.