Alterations of short-term heart rate variability in periinduction period of general anaesthesia with two intravenous anaesthetics.

INTRODUCTION Alterations of the parameters of heart rate variability, phenomenon associated with autonomic nervous system balance, have been shown as a possibly very important factor for monitoring of cardiocirculatory system in the perioperative period. Periinduction period of general anaesthesia is very important with significant changes of haemodynamics what could be reflected in the changes of the parameter of heart rate variability. METHODS A hundred patients of ASA I and ASA II status who were scheduled for elective abdominal surgical procedures of moderate stress response, were randomly assigned to group I and group II, who were administered propofol or thiopentone as induction anaesthetic, respectively. Monitoring during periinduction period included of monitoring of mean blood pressure (noninvasively), heart rate, pulseoxymetry and recording of electrocardiogram by holter ECG recorder for further analysis of heart rate variability, in four time segments in periinduction period: Tp, T1, T2, T3. Data were presented as mean values of absolute values of the power of the total spectrum of heart rate variability, mean values of the spectrum of low frequency band (LF), mean values of the high frequency range, and the ratio LF/HF. RESULTS Analysis of the values of hemodynamic parameters has shown decrease of mean arterial blood pressure after induction of anaesthesia with intravenous anesthetics thiopental or propofol, with simultaneous changes of heart rate in the four time segments in periinduction period, without statistically significant changes between the groups. Analysis of the values of parameters of heart rate variability measured in the frequency domain has shown changes of mean values of the absolute values of total power spectrum, mean values of the power of low frequency spectrum and mean values of the power of high power spectrum with reduction of the values of total power spectrum, the power of low frequency spectrum and the power of high frequency spectrum, most pronounced just after induction of anaesthesia with slight increase of the values of total power spectrum and individual components of the spectrum of heart rate variability in the later postinduction period, without statistically significant differences between the groups. CONCLUSION The results have shown that in the groups of patients who underwent induction of general anaesthesia with propofol or thiopentone, there have been reductions of the total spectral power and the power of the spectrum of low frequency components and high frequency components with variations in the relationship between the components in the different periods of periinduction time.