title: Changes in respiratory pattern and arterial blood gases during sedation with propofol or midazolam in spinal anesthesia.
abstract: OBJECTIVE
  To investigate changes in respiratory pattern and arterial blood gases during sedation with propofol or midazolam in spinal anesthesia.
  
  
  METHODS
  Randomized, placebo-controlled study.
  
  
  METHODS
  Operating room of a university-affiliated hospital.
  
  
  METHODS
  40 ASA physical status I and II patients who required spinal anesthesia.
  
  
  METHODS
  Spinal anesthesia with tetracaine and subsequent sedation with propofol (n = 15), midazolam (n = 15), or placebo (n = 10) was performed.
  
  
  METHODS
  Respiratory pattern [rib cage contribution to the tidal volume (%RC) and phase shift between rib cage and abdominal movements (PSrc-ab)] with a respiratory inductive plethysmograph (Respigraph) and arterial blood gas analysis (pH, pO2, and pCO2) were recorded.
  
  
  RESULTS
  Spinal anesthesia per se increased %RC by 35% without changing PSrc-ab values (1.00). Sedation with propofol and midazolam decreased %RC by 60% and by 40%, respectively. PSrc-ab increased in both groups following sedation, and the increase in this parameter was higher in the propofol group (1.12) than in the midazolam group (1.04). In the placebo group, %RC decreased by 20% without any change in PSrc-ab. The decrease in pO2 was more significant in the propofol group (65.1 mmHg) than in the midazolam (74.2 mmHg) and placebo (83.1 mmHg) groups.
  
  
  CONCLUSIONS
  Significant decreases in %RC and pO2 during propofol sedation seem to depend on paradoxical respiration due, in part, to upper airway obstruction; therefore, attention should be directed to the respiratory pattern during sedation, especially with propofol.
authors.affiliation: Department of Anesthesiology, Sapporo Medical University, School of Medicine, Hokkaido, Japan. yamakage@sapmed.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Yamakage
authors.forename: Y
authors.initials: Y
authors.lastname: Kamada
authors.forename: M
authors.initials: M
authors.lastname: Toriyabe
authors.forename: Y
authors.initials: Y
authors.lastname: Honma
authors.forename: A
authors.initials: A
authors.lastname: Namiki
mesh_terms: D000328:Adult; D000368:Aged; D000775:Anesthesia, Spinal; D002245:Carbon Dioxide / Q000097:blood*; D005260:Female; D006801:Humans; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D008297:Male; D008874:Midazolam / Q000494:pharmacology*; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D015742:Propofol / Q000494:pharmacology*; D012119:Respiration / Q000187:drug effects*
chemical_list: D006993:Hypnotics and Sedatives; D002245:Carbon Dioxide; D008874:Midazolam; D010100:Oxygen; D015742:Propofol