title: Effect of conscious sedation on cardiac autonomic regulation during colonoscopy.
abstract: BACKGROUND
  Colonoscopy is associated with cardiovascular events including hypotension, hypertension, and myocardial ischemia. The pathogenetic mechanisms of these cardiovascular events are unknown, but there is evidence that the autonomic nervous system may play a role. Conscious sedation is often used to relieve the inconvenience caused by the procedure. In this study, we evaluated the effects of sedation on cardiac autonomic regulation during colonoscopy.
  
  
  METHODS
  One hundred and eighty patients undergoing elective colonoscopy were prospectively randomized into three groups: (i) sedation with intravenous midazolam (midazolam group); (ii) sedation with intravenous saline (placebo group); and (iii) no intravenous cannula (control group). Continuous electrocardiogram was recorded prior to, during, and after the colonoscopic procedure. Heart rate variability (HRV) was assessed by means of the power spectral analysis; the powers of low-frequency (LF 0.04-0.15 Hz) and high-frequency (HF 0.15-0.40 Hz) components were calculated.
  
  
  RESULTS
  Intubation of the colonoscope increased the LF component of HRV and decreased HF power in all study groups compared to baseline recording. Furthermore, compared to baseline, the LF/HF ratio--a marker of cardiac sympathetic regulation--increased during intubation in the midazolam (P < 0.001) and placebo (P < 0.05) groups, with no change in the control group. During intubation the midazolam group presented with higher LF and lower HF power than placebo (P < 0.001) and control groups (P < 0.01). Accordingly, the LF/HF ratio was higher in the midazolam group than in the placebo (P < 0.05) or control groups (P < 0.05).
  
  
  CONCLUSIONS
  Midazolam potentiates the dominance of the sympathetic nervous system induced by colonoscopy. Therefore, conscious sedation with midazolam may contribute to the occurrence of cardiovascular events during colonoscopy.
authors.affiliation: Dept. of Medicine, Kuopio University Hospital, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Ristikankare
authors.forename: R
authors.initials: R
authors.lastname: Julkunen
authors.forename: T
authors.initials: T
authors.lastname: Laitinen
authors.forename: S X
authors.initials: SX
authors.lastname: Wang
authors.forename: M
authors.initials: M
authors.lastname: Heikkinen
authors.forename: E
authors.initials: E
authors.lastname: Janatuinen
authors.forename: J
authors.initials: J
authors.lastname: Hartikainen
mesh_terms: D003113:Colonoscopy; D016292:Procedural Sedation / Q000009:adverse effects; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000294:innervation* / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D006993:Hypnotics and Sedatives / Q000008:administration & dosage* / Q000009:adverse effects; D008297:Male; D008874:Midazolam / Q000008:administration & dosage* / Q000009:adverse effects; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011292:Premedication; D011446:Prospective Studies
chemical_list: D006993:Hypnotics and Sedatives; D008874:Midazolam