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.
Anesthesia* ; Electrocardiography ; Entropy* ; Heart Rate ; Homeostasis ; Humans ; Hypertension* ; Informed Consent

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.
Anesthesia* ; Electrocardiography ; Freedom ; Heart Rate* ; Heart* ; Humans ; Informed Consent ; Noise ; Nonlinear Dynamics*