Heart Rate Variability as a Promising Tool to Predict Hypotension

To the Editor: Reich et al. (1) recently published predictors of hypotension after induction of general anesthesia. Postinduction hypotension was significantly correlated with ASA status, baseline hypotension, and use of propofol as the induction hypnotic. In our view, these clinical variables may be reasonably completed by noninvasive analysis of heart rate variability (HRV) as a surrogate for the drive of the autonomous nervous system. Chamchad et al. (2) found a significant correlation of nonlinear HRV dimension analysis with the incidence of hypotension occurring after spinal anesthesia for cesarean delivery. More recently we demonstrated that HRV-derived variables were able to predict hypotension after spinal anesthesia in pregnant women (3) and elderly men (4). For this purpose, our group has investigated the ratio of low to high frequency peaks of the power spectrum (LF/HF) reflecting the balance of sympathetic and parasympathetic activity. A significant correlation between postspinal hypotension and a specific threshold LF/HF ratio was shown. These results have not been confirmed in patients undergoing general anesthesia. Nevertheless, HRV analysis may help predict the risk of hypotension in this patient population. Robert Hanss, MD Peter H. Tonner, MD Jens Scholz, MD Berthold Bein, MD Department of Anesthesiology and Intensive Care Medicine University Hospital Schleswig-Holstein, Campus Kiel Kiel, Germany [email protected]