Cardiovascular reflexes during anesthesia induction and tracheal intubation in elderly patients: The influence of thoracic epidural anesthesia

Abstract

Study Objectives: To determine whether thoracic epidural anesthesia performed prior to general anesthesia provides hemodynamic protection from the stress of laryngoscopy and tracheal intubation; to assess the autonomic reflex response to epidural anesthesia, general anesthesia, and airway stimulation. Design: Randomized, unblind, controlled study. Patients and Setting: 20 elderly (over 60) patients scheduled for colonic or gastric surgery at a university medical center. Interventions: All patients (n = 10, in each group) underwent a standardized anesthesia induction sequence that included fentanyl 2 μg/kg, thiopental sodium 3 to 5 mg/kg (up to loss of eyelid reflex), and vecuronium 0.1 mg/kg followed by laryngoscopy and tracheal intubation. Before general anesthesia, thoracic epidural anesthesia was performed with plain 1% lidocaine in the epidural group. Preoperatively, baroreflex function was assessed by the Valsalva maneuver and the cough test. Spectral analysis of heart rate (HR) variability was performed before as well as during anesthesia. Measurements and Main Results: There were no differences between the two groups in basal hemodynamics and autonomic reflex status. Thoracic epidural anesthesia (median upper level at T 2, median lower level at L 2) was associated with stable hemodynamics, preservation of baroreflex sensitivity, and increased ratio of low to high frequency ( LF HF ) components of HR variability, suggesting withdrawal of vagal activity. In both groups, general anesthesia induction was associated with decreased total HR variability and tracheal intubation was followed by increased LF HF ratio, reflecting cardiac sympathetic activation. Patients with thoracic epidural anesthesia presented significant attenuation of the maximal rise in mean arterial pressure, and the increase in HR tended to be lower although not significantly. Conclusions: Thoracic epidural blockade combined with general anesthesia was associated with preserved baroreflex function, and it afforded hemodynamic protection during laryngoscopy and tracheal intubation.