title: Baroreflex impairment and morbidity after major surgery.
abstract: BACKGROUND
  Baroreflex dysfunction is a common feature of established cardiometabolic diseases that are most frequently associated with the development of critical illness. Laboratory models show that baroreflex dysfunction impairs cardiac contractility and cardiovascular performance, thereby increasing the risk of morbidity after trauma and sepsis. We hypothesized that baroreflex dysfunction contributes to excess postoperative morbidity after major surgery as a consequence of the inability to achieve adequate perioperative tissue oxygen delivery.
  
  
  METHODS
  In a randomized controlled trial of goal-directed haemodynamic therapy (GDT) in higher-risk surgical patients, baroreflex function was assessed using the spontaneous baroreflex sensitivity (BRS) method via an arterial line placed before surgery, using a validated sequence method technique (one beat lag). The BRS was calculated during the 6 h postoperative GDT intervention. Analyses of BRS were done by investigators blinded to clinical outcomes. The primary outcome was the association between postoperative baroreflex dysfunction (BRS <6 mm Hg s(-1), a negative prognostic threshold in cardiovascular pathology) and early postoperative morbidity. The relationship between baroreflex dysfunction and postoperative attainment of preoperative indexed oxygen delivery was also assessed.
  
  
  RESULTS
  Patients with postoperative baroreflex dysfunction were more likely to sustain infectious {relative risk (RR) 1.75 [95% confidence interval (CI): 1.07-2.85], P=0.02} and cardiovascular morbidity [RR 2.39 (95% CI: 1.22-4.71), P=0.008]. Prolonged hospital stay was more likely in patients with baroreflex dysfunction [unadjusted hazard ratio 1.62 (95% CI: 1.14-2.32), log-rank P=0.004]. Postoperative O2 delivery was 36% (95% CI: 7-65) lower in patients with baroreflex dysfunction in those not randomly assigned to GDT (P=0.02).
  
  
  CONCLUSIONS
  Baroreflex dysfunction is associated with excess morbidity, impaired cardiovascular performance, and delayed hospital discharge, suggesting a mechanistic role for autonomic dysfunction in determining perioperative outcome.
  
  
  BACKGROUND
  ISCRTN76894700.
authors.affiliation: Royal Perth Hospital, Perth, WA, Australia Clinical Physiology, Department of Medicine, University College London, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Toner
authors.affiliation: Department of Anaesthesia, Royal Free Hospital, Pond Street, London, UK.
authors.forename: N
authors.initials: N
authors.lastname: Jenkins
authors.affiliation: Clinical Physiology, Department of Medicine, University College London, London, UK William Harvey Research Institute, Barts and The London Medical School, Queen Mary University of London, London, UK Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK g.ackland@qmul.ac.uk.
authors.forename: G L
authors.initials: GL
authors.lastname: Ackland
mesh_terms: D000368:Aged; D001341:Autonomic Nervous System / Q000502:physiology; D017704:Baroreflex / Q000502:physiology*; D004311:Double-Blind Method; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D009017:Morbidity; D011183:Postoperative Complications / Q000209:etiology*
keywords: autonomic nervous system; baroreflex; postoperative complications