Change of Heart Rate Variability before and after General Anesthesia

Abstract

Background: This study assessed the changes in the heart rate variability (HRV) indices, which are used to measure the autonomic nervous system function during general anesthesia (GA), and compared the result of the awake state. Methods: Patients undergoing an explo-laparotomy were anesthetized with either isoflurane (Group I, n = 20) or sevoflurane (Group S, n = 20) added to a mixture of nitrous oxide and oxygen. Frequency-domain analysis of the HRV indices using fast Fourier transformation (FFT) resulted in a power spectrum with a very low (VLF), low (LF), and high frequency (HF) and calculated normalized LF (nuLF), normalized HF (nuHF), and LF/HF ratios before and after GA. Time-domain analysis was performed and the pNN50 (proportion of successive RR intervals [RRI] ＞ 50 ms in relation to the total RRI), RMSSD (root mean square of the successive differences in the RRI), standard deviation 1 (SD1) and standard deviation 2 (SD2) from the Poincare plots, HRV triangular index, and TINN (triangular interpolation of NN interval histogram) were also calculated before and after GA. Results: The VLF, LF, HF, nuLF, and LF/HF ratio during GA decreased by 45.2, 95.1, 83.1, 27.3, and 17.4%, respectively, compared with the awake state. However, the nuHF significantly increased. The RMSSD, pNN50, SD1, SD2, HRV triangular index, and TINN also decreased 62.0, 69.2, 62.0, 61.7, 62.4, and 52.4%, respectively. Groups I and S produced similar alterations in the studied parameters during GA. Conclusions: GA reduced all the HRV indices studied except for the nuHF.