Assessment of autonomic cardiovascular changes associated with recovery from anaesthesia in children: a study using spectral analysis of blood pressure and heart rate variability

Abstract

Recovery from anaesthesia is associated with large changes in cardiovascular autonomic activity, which are poorly documented in children. This study was undertaken to investigate the cardiovascular autonomic activity in anaesthetized and recovering children, using a noninvasive approach based on spectral analysis of heart rate (HR) and blood pressure (BP) variability. Ten children (aged 5-13 years) undergoing major surgery were studied. Continuous HR and BP were recorded using a noninvasive device during deep anaesthesia and recovery. Spectral analysis was used to determine the main oscillatory components of HR and BP signals. For each power spectrum, the frequency components were identified as follows (i): the low frequency (LF) component (0.04-0.14 Hz) both parasympathetically and sympathetically mediated for HR and corresponding to vasomotor sympathetic modulation for BP; and (ii) the high frequency (HF) component (0.2-0.6 Hz) parasympathetically mediated for HR, and reflecting mechanical influence of ventilation on cardiac output for BP. In addition, the LF : HF ratio for HR, reflecting the cardiac sympathovagal balance, was calculated. Under deep anaesthesia, HR variability and BP variability were very low and mainly due to mechanical influence of intermittent positive pressure ventilation. Conversely, the recovery period was associated with a marked increase of HR and BP overall variability. Compared to anaesthesia, spectral analysis of HR and BP revealed that the LF component of BP and HR spectra increased 40-fold during recovery; the LF : HF ratio of HR was also increased during recovery (0.1 +/- 0.1 versus 1.3 +/- 1.2, P=0.008). The results of this study demonstrate that the recovery period is associated with an increase of cardiovascular sympathetic drive in children after major surgery.

Blood pressure-induced physiological strain variability modulates wall structure and function in aorta rings

“…Limitations of this study result from the experimental setup for measuring aorta mechanics, which are known to vary in rats from in vitro to in situ and in vivo conditions [6]. Blood pressure variability is also significantly reduced during anesthesia in children [ 5]. Thus, we may have underestimated the tails of the strain distribution in figure 1(B) due to anesthesia.…”

“…Second, changes in strain variability, due to increased blood pressure variability in patients with hypertension and aging [23], may alter the contractile properties of the aorta as well as its healthy homeostatic beat-to-beat mechanotransduction. Third, during medical interventions involving long-term anesthesia in human subjects [5], strain variability decreases which may reduce contractility and disorganize the ECM of the vessel wall. Finally, the classical view that aortic stiffness can mostly be attributed to the ECM has recently been challenged demonstrating that VSMCs contribute substantially to the stiffness of the aorta in aging and hypertension [8, 29, 31].…”