ORIGINAL RESEARCH Baroreflex sensitivity variations in response to propofol anesthesia: comparison between normotensive and hypertensive patients Guadalupe Dorantes Mendez • Federico Aletti • Nicola Toschi • Antonio Canichella • Mario Dauri • Filadelfo Coniglione • Maria Guerrisi • Maria G. Signorini • Sergio Cerutti • Manuela Ferrario Received: 30 July 2012 / Accepted: 27 December 2012 / Published online: 13 January 2013 Ó Springer Science+Business Media New York 2013 Abstract The aim of this paper is to compare baroreflex sensitivity (BRS) following anesthesia induction via pro- pofol to pre-induction baseline values through a systematic and mathematically robust analysis. Several mathematical methods for BRS quantification were applied to pre-oper- ative and intra-operative data collected from patients undergoing major surgery, in order to track the trend in BRS variations following anesthesia induction, as well as following the onset of mechanical ventilation. Finally, a comparison of BRS trends in chronic hypertensive patients (CH) with respect to non hypertensive (NH) patients was performed. 10 NH and 7 CH patients undergoing major surgery with American Society of Anesthesiologists clas- sification score 2.5 ± 0.5 and 2.6 ± 0.5 respectively, were enrolled in the study. A Granger causality test was carried out to verify the causal relationship between RR interval duration and systolic blood pressure (SBP), and four dif- ferent mathematical methods were used to estimate the BRS: (1) ratio between autospectra of RR and SBP, (2) transfer function, (3) sequence method and (4) bivariate closed loop model. Three different surgical epochs were considered: baseline, anesthetic procedure and post- intubation. In NH patients, propofol administration caused a decrease in arterial blood pressure (ABP), due to its va- sodilatory effects, and a reduction of BRS, while heart rate (HR) remained unaltered with respect to baseline values before induction. A larger decrease in ABP was observed in CH patients when compared to NH patients, whereas HR remained unaltered and BRS was found to be lower than in the NH group at baseline, with no significant changes in the following epochs when compared to baseline. To our knowledge, this is the first study in which the autonomic response to propofol induction in CH and NH patients was compared. The analysis of BRS through a mathematically rigorous procedure in the perioperative period could result in the availability of additional information to guide ther- apy and anesthesia in uncontrolled hypertensive patients, which are prone to a higher rate of hypotension events occurring during general anesthesia induction. Keywords Baroreflex sensitivity  Causality  Anesthesia  Blood pressure  Heart rate Abbreviations HR Heart rate SBP Systolic blood pressure DBP Diastolic blood pressure ABP Arterial blood pressure BR Baroreflex BRS Baroreflex sensitivity TF Transfer function method LF Low frequency HF High frequency TP Total power CH Chronic hypertensive NH Non hypertensive G. Dorantes Mendez  F. Aletti  M. G. Signorini  S. Cerutti  M. Ferrario (&) Department of Bioengineering, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, MI, Italy e-mail: manuela.ferrario@polimi.it N. Toschi  A. Canichella  M. Guerrisi Medical Physics Section, Faculty of Medicine, University of Rome ‘‘Tor Vergata’’, Via Montpellier 1, 00133 Rome, Italy M. Dauri  F. Coniglione Department of Anesthesia and Intensive Care Medicine, Faculty of Medicine, University of Rome ‘‘Tor Vergata’’, Via Montpellier 1, 00133 Rome, Italy 123 J Clin Monit Comput (2013) 27:417–426 DOI 10.1007/s10877-012-9426-1