Power Spectral Analysis of Heart Rate Variability during Total Spinal Anesthesia in Rats / 대한마취과학회지

BACKGROUND: Total spinal anesthesia (TSA) anesthetizes cranial nerves as well as peripherial nerves, leading to specific circulatory perturbations related to autonomic imbalance between sympathetic and parasympathetic tone. Heart rate variability (HRV) result from moment-to-moment changes in sympathetic and parasympathetic activity in response to many conditions. Using a power spectral analysis of heart rate variability, we evaluated the effect of TSA on the changes in the autonomic nervous system. METHODS: Twenty-four Sprague-Dawley rats, during halothane anesthesia, were placed in a stereotaxic head holder. Polyethylene tubing (PE-10) was passed caudally from the cisterna magna, and these rats were anesthetized by a urethane intraperitoneal injection (1.5 g/kg). Succinylcholine was infused intravenously at 1 mg/kg/min. During mechanical ventilation, ECG signals and mean arterial blood pressure were recorded for 5 min after a period of 10 min of anesthetic stabilization (baseline). Lidocaine (40 mg/kg) was administered intrathecally and then two subsequent 5-min ECG signals and mean arterial blood pressure were recorded (TSA 0 5 min, 5 10 min). A power spectral analysis of the data was computed using a short-time Fourier transform. The spectral peaks within each measurement were calculated; low frequency area (0.25 0.75 Hz), high frequency area (0.75 3.0 Hz), total frequency area (0.25 3.0 Hz). RESULTS: Mean R-R interval increases progressively during the 5 minutes after TSA but mean blood pressure decreases to the level of blood pressure of TSA within 2 minutes after TSA (p < 0.05). TSA diminished HRV within 2 minutes after a spinal injection of lidocaine (p < 0.05). CONCLUSIONS: These results suggest that total spinal anesthesia depresses both sympathetic and parasympathetic tone within 2 minutes.

Hemodynamic Effect of Propofol and Esmolol under Isoflurane Anesthesia in Dogs / 대한마취과학회지

BACKGROUND: Propofol has gained widespread popularity but it should at least be questioned in the presence of heart rate lowering medications such as beta-blockers. Esmolol, due to its ultrashort action and cardioselective properties, has been shown to be safe and effective for use in intraoprative tachycardia and hypertension. The purpose of this study is to evaluate the hemodynamic effects of esmolol and propofol under isoflurane anesthesia in dogs. METHODS: Six-mongrel dogs were induced with thiopental, intubated and ventilated with a mixture of isoflurane (1-1.5 vol%) and oxygen. A pulmonary artery catheter was placed via femoral vein and the femoral artery was cannulated. After stabilization, baseline hemodynamic measurements (HR, MAP, CO, SVR) were obtained. Measurements were repeated 5 and 15 minutes after injection of propofol (2 mg/kg), esmolol (1 mg/kg), and additional esmolol (1 mg/kg) for 30 seconds. Data was analyzed by repeated measurement of ANOVA. P < 0.05 was considered significant. RESULTS: Propofol produced no change in heart rate, MAP, CO and SVR. Heart rate decreased significantly during esmolol administration and remained decreased up to 15 minutes after the injection whereas the MAP, CO and SVR showed no significant changes. CONCLUSIONS: We have demonstrated that the decrease in heart rate continued up to 15 minutes after esmolol administration. These findings suggest that concomittent administration of propofol and esmolol requires monitoring of the heart rate after a bolus intravenous injection of esmolol.

The Effect of Brimonidine Premedication on the Sympathetic Nervous System during Ketamine Anesthesia in the Ratv / 대한마취과학회지

BACKGROUND: The use of ketamine as the sole anesthetic induces marked central sympathetic stimulation, causing an increase of heart rate and blood pressure. alpha2-receptor agonist has been demonstrated to attenuate many of these undesirable effects when used as a premedicant. Brimonidine is a new and highly selective alpha2-receptor agonist, and rauwolscine is a selective alpha2-receptor antagonist with little affinity for imidazoline receptors. Using power spectral analysis of heart rate variability, this study examines the effect of brimonidine premedication during ketamine anesthesia on the changes in the autonomic nervous system. METHODS: From 57 Sprague-Dawley rats, 12 rats were anesthetized by urethane (U Group, 1.5 g/kg), 18 rats by ketamine (K Group, 100 mg/kg, 2 mg/kg/min continuous infusion) intraperitoneal injection after saline premedication. Brimonidine (BK Group, 30 microgram/kg, n=15), brimonidine with rauwolscine (BRK Group, 30 microgram/kg, 20 mg/kg, n=12) were adminstered as a premedicant before induction of ketamine anesthesia. ECG signals were recorded for 5 min after a period of 10 min of anesthetic stabilization. Power spectal analysis of the data was computed, using short-time Fourier transform. The spectral peaks within each measurement were calculated; a low frequency area (0.04~1.0 Hz), a high frequency area (1.0~5.0 Hz), and a total frequency area (0.04~5.0 Hz) were measured. RESULTS: The results documented that the K Group showed sympathetic activation as compared with the U Group (p<0.001). The BK Group showed sympathetic depression compared with the K and BRK Groups (p<0.001). There were no significant differences in sympatho-vagal balance between the K and BRK Groups. CONCLUSIONS: These results suggest that premedication with brimonidine is effective in attenuating the sympathetic stimulatory effect of ketamine.

Correlation between the Degree of Bradycardia in Strabismus Surgery with Linear and Nonlinear Analysis of Preoperative Electrocardiogram / 대한마취과학회지

BACKGROUND: Severe bradycardia occurring in strabismus surgery is unpredictable and may lead to cardiac arrest. If we identify patients who have risk of severe bradycardia during strabismus surgery, it is helpful to provide a more meticulous anesthesia. In this study, we investigated the correlation between the degree of bradycardia and indices of power spectral analysis and nonlinear dynamic data analysis of preoperative ECG. METHODS: ECG was collected for twenty minutes from strabismus patients (n = 93). No premedicants were administered. After administration of anesthesia and traction of extraocular muscle, the lowest heart rate was recorded. We calculated the correlation coefficient between the power spectral density, approximate entropy and correlation dimension of preoperative ECG and the difference between preoperative and lowest HR. RESULTS: As the difference between the preoperative heart rate and the intraoperative bradycardia increased, the preoperative ECG showed a low total power (r = 0.27, P = 0.016), low low-frequency power (r = 0.31, P = 0.049), low high-frequency power (r = 0.30, P = 0.007) and high ratio of low to high-frequency power (r = 28, P = 0.03). There was no correlation between bradycardia and approximate entropy and correlation dimension, respectively. CONCLUSIONS: There was a correlation between indices of power spectral analysis of preoperative ECG and degree of bradycardia during strabismus surgery. Therefore we take into consideration preoperative ECG and its analytic indices in order to provide careful preparation for high risk patients who exhibit a tendency to severe bradycardia.

Power Spectral Components Analysis of Heart Rate Variability during Propofol-O2-N2O Anesthesia / 대한마취과학회지

BACKGROUND: Beat-to-beat heart rate variability (HRV) is caused by the fluctuating balance of sympathetic and parasympathetic tone. Analysis of heart rate variations may provide important clinical information and the influence of anesthesia on the autonomic nervous system. METHODS: We studied 18 ASA I female patients undergoing propofol-O2-N2O anesthesia for transabdominal hysterectomy and analyzed the HRV using power spectral analysis (PSA) at preinduction period, 2~5 minutes after induction, and 30~33 minutes after skin incision. RESULTS: The powers in all frequency bands decreased, but the decrease in low+middle frequency power was less than that in high frequency power during 2~5 minutes after induction. At 30~33 minutes after skin incision, all frequency bands and ratio of low middle/high frequency power spectra recovered and were not significantly different from those of before induction. CONCLUSIONS: Propofol-N2O-O2 anesthesia depress autonomic nervous system with relative preservation of sympathetic components. However autonomic nervous system and sympathetic/parasympathetic balance during operation recovered to the pre-anesthetic pattern, probably due to surgical stimuli and stress.

Changes of Heart Rate Variability during Anesthesia in Hypertensive Patients by Nonlinear Dynamics / 대한마취과학회지

BACKGROUND: Heart rate variability (HRV) is characterized by a variety of linear, non-linear, periodic and non-periodic oscillations. The aim of the present study was mainly to investigate the characteristics of nonlinear dynamics of HRV of the hypertensive patients by anesthesia comparing with the normotensive patients. METHODS: With informed consent, unpremedicated normotensive (n=20) and the hypertensive patients (n=22) were included in this study. ECG data were collected from 10 minutes before induction to 15 minutes after induction. Collected ECG data were stored into computer binary files. We calculated correlation dimensions (CD, degree of freedom of system), 1/f noise (beta, nonlinearity) and Hurst exponents (HE, roughness of signals) from the collected ECG data. RESULTS: During resting state, CD of the hypertensive patients was significantly lower than that of the normotensive patients (P<0.05). During maintenance of anesthesia, there was no difference of CD between the two groups. CD of two groups were decreased significantly after anesthesia (P<0.001). The values of and HE of two groups were not different during resting state and maintenance of anesthesia. But the values of and HE of two groups were increased significantly after anesthesia (P<0.001). CONCLUSION: As the CD of the hypertensive patients is lower than of the normotensive patients during resting state, the degree of freedom of heart rate control system of the hypertensive patients is more smaller than that of the normotensive patients. Decreasing of CD after anesthesia in two groups means that degree of freedom of heart rate control system is decreased by anesthesia. Increasing of 1/f noise after anesthesia in two groups means that nonlinearity of heart rate variability is decreased by anesthesia. Increasing of HE after anesthesia in two groups means that roughness of heart rate variability is decreased by anesthesia.

Approximate Entropy of Hypertension: Effect of Anesthesia / 대한마취과학회지

BACKGROUND: Recently, measurement of heart rate variability and the nonlinear complexity of heart rate dynamics have been used as indicators of cardiovascular health. Hypertensive patients showed alternation of cardiovascular homeostasis. We designed this study to evaluate the effect of anesthesia in hypertensive patients with approximate entropy (ApEn), representing the nonlinear complexity. METHODS: With informed consent, none premedicated normotensive (n=18) and hypertensive patients (n=18) were included in this study. ECG data were collected from 10 minutes before induction to 15 minutes after induction. Collected ECG data were stored into computer binary files. We calculated ApEn from the collected ECG data. RESULTS: Before induction, ApEn of hypertensive patients was significantly lower than that of normotensive patients (p<0.05). During induction and maintenance of anesthesia, there was no difference of ApEn between the two groups. ApEn of normotensive patients during induction and maintenance of anesthesia was significantly lower than that of pre-induction (p<0.05). ApEn during maintenance of anesthesia was lower than that of induction of anesthesia (p<0.05). ApEn of hypertensive group during maintenace of anesthesia was significantly lower than that of pre-induction of anesthesia (p<0.05). CONCLUSIONS: As the ApEn of hypertensive patients is lower than that of normotensive patients during pre-inducton period, the heart rate dynamics of hypertensive patients is more regular normotensive patients. The anesthesia is deepened, the heart rate dynamics of the both group is more regular. During the maintenance of anesthesia, the regularity of the heart rate dynamics that not different in both group from the results.

A Comparison of 10% Lidocaine Spray and Intravenous 2% Lidocaine on Mean ArterialPressure and Heart Rate Following Tracheal Intubation / 대한마취과학회지

BACKGROUND: Laryngoscopy and tracheal intubation for general anesthesia are potent stimuli to the cardiovascular system due to sympathetic stimulation. The aim of this study was to compare the hemodynamic responses with different administration routes of lidocaine on blood pressure and heart rate changes associated with tracheal intubation. METHODS: Sixty patients were randomly assigned to spray group (Group 1, n=20) received 10% lidocaine 1.5 mg/kg spray to intratracheally immediately before tracheal intubation, IV group (Group 2, n=20) received 2% lidocaine 1.5 mg/kg intravenously before 90 sec tracheal intubation and control group (Group 3, n=20). Anesthesia was induced with thiopental 5 mg/kg IV, vecuronium 0.1 mg/kg and 50% N2O-O2- 2vol % enflurane. After 5 minutes, tracheal intubation was performed. Mean arterial pressure and heart rate were measured at preintubation and immediately postintubation, 1, 3, 5 mins after tracheal intubation. RESULTS:The differences of mean arterial pressure which were measured at preintubation and immediately postintubation and 1 minute after intubation in group 1 were significantly lower than those in other group (p<0.05). The differences of heart rate which measured at preintubation and 1 minute after intubation were lower than those in group 3 (p<0.05). CONCLUSIONS: For the suppression of sympathetic stimulation following tracheal intubation, 10% lidocaine spray to the laryngotrachea is an effective method to suppress cardiovascular response.

The Effects of Urapidil on Changes of Arterial Blood Pressure and Heart Rate to Endotracheal Intubation / 대한마취과학회지

BACKGROUND: Urapidil is a new antihypertensive agent known to diminish total peripheral vascular resistance by postsynaptic alpha 1-adrenergic blockade and central sympatholytic activity. The purpose of this study was to determine its effectiveness and safety in preventing hemodynamic responses to endotracheal intubation under general anesthesia. METHODS: Thirty normotensive, ASA physical status I patients for elective surgery were selected randomly. They were divided into three groups(Group 1: control group with saline, Group 2: urapidil 0.4 mg/kg, Group 3: urapidil 0.5 mg/kg, n=10 in each group). The drugs were injected 3 minutes before induction with thiopental sodium(4 mg/kg) and succinylcholine(1 mg/kg). Endotracheal intubation was performed 5 minutes after the drugs injection. After endotracheal intubation, vecuronium 0.1 mg/kg was injected and 50% nitrous oxide in oxygen and 2Vol% enflurane were inhaled. We measured the blood pressure and the heart rate with noninvasive method at one minute interval for 5 minutes. RESULTS: In group 3, no significant increase in systolic blood pressure after endotracheal intubation was noted(p<0.05). Urapidil groups showed increase in heart rate at 1, 2 minutes after urapidil injection(p<0.05) and did not blunt increase in heart rate after endotracheal intubation. The side effects of urapidil(hypotension, dizziness, headache and chest tightness) occured in a patient of group 3. CONCLUSIONS: We found that the blood pressure response was effectively controlled, but the change in heart rate was not controlled by urapidil 0.5 mg/kg injection before induction.

The Effect of Different Dosage of Propofol on Cardiovascular Responses to Tracheal Intubation in Hypertensive Patients / 대한마취과학회지

BACKGROUND: Laryngoscopy and endotracheal intubation are potent stimuli that increase heart rate and blood pressure. Especially, hypertensive patients are more prone to have significant increase in heart rate and blood pressure and cardiac complications such as arrythmia, myocardial ischemia and infarction can lead to fatal situation. This study was designed to evaluate the effectiveness of different dosage of propofol on cardiovascular responses to tracheal intubation in hypertensive patients. METHODS: Sixty hypertensive patients, ASA PS 1 or 2, scheduled for elective surgery were selected randomly. They were divided into three groups(Group 1: propofol 2.0 mg/kg, Group 2: propofol 2.5 mg/kg, Group 3: propofol 3.0 mg/kg, n=20 in each group). Induction of Anesthesia was started with propofol 2.0 mg/kg(Group 1), 2.5 mg/kg(Group 2), 3.0 mg/kg(Group 3) and succinylcholine(1 mg/kg). After tracheal intubation, pancuronium bromide 0.08 mg/kg was injected, 50 % nitrous oxide in oxygen and 2 % enflurane were inhaled. Using noninvasive automatic blood pressure monitor(CRITIKON DINAMAP TM 1846SX, USA), blood pressure(systolic, diastolic, and mean arterial pressure) and heart rate were measured at 4 points; 1) as the control value, on arrival to operating room, 2) 1 minute after tracheal intubation, 3) 3 minutes after intubation, 4) 5 minutes after intubation. RESULTS:In group 3, systolic, diastolic pressure and mean arterial pressure at 1 minutes, 3 minutes, 5 minutes after intubation were less increased than group 1, 2 and blood pressure response was more effectively blunted than heart rate response CONCLUSIONS: we suggested that 3.0 mg/kg of propofol for the induction of anesthesia could blunt hemodynamic changes caused by laryngoscopy and endotracheal intubation in hypertensive patients, but we had to give attention to the side effect until postoperative period.