Increased non-stationarity of heart rate during general anaesthesia with sevoflurane or desflurane in children

Background. During general anaesthesia, the most prominent change in heart rate variability (HRV) is a decrease in the magnitude of heart rate (HR) oscillation in the high- and low-frequency ranges. In children receiving sevoflurane or desflurane, we observed a significant increase in HR non-stationarity, that is, a significant change of mean HR over time. The aim of our study was to describe this increased non-stationarity and compare it with the decrease in the magnitude of HR oscillation. Methods. Sixty children received sevoflurane (n=30) or desflurane anaesthesia (n=30). The magnitude of HR oscillation and non-stationarity during pre-anaesthesia and anaesthesia were measured by spectral and Hurst analyses using structure function, respectively. Results. Low- and high-frequency powers decreased significantly and the very-short-term (2 <=tau <= 8 s, H-alpha) and short-term Hurst exponent (8 <=tau <= 45 s, H-beta) increased significantly during the anaesthetic period compared with the pre-anaesthetic period, regardless of the anaesthetic agent [sevoflurane: mean (SD) H-alpha 0.414 (0.169) vs 0.252 (0.0655), H-beta 0.481 (0.169) vs 0.078 (0.0409); desflurane H-alpha 0.336 (0.171) vs 0.261 (0.0614), H-beta 0.471 (0.221) vs 0.0813 (0.049)]. Stepwise discriminant analysis showed that the short-term Hurst exponent was better than the spectral indices at differentiating between the pre-anaesthetic period and anaesthetic period. Conclusion. During sevoflurane and desflurane anaesthesia in children, there is a significant increase in very-short-term and short-term HR non-stationarity. Furthermore, the greater short-term non-stationarity differentiates better between the pre-anaesthesia and anaesthesia than the decreased magnitude of HR oscillation in the high- and low-frequency ranges.