Changes in respiratory pattern and arterial blood gases during sedation with propofol or midazolam in spinal anesthesia.
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.
Yamakage
M
M
Department of Anesthesiology, Sapporo Medical University, School of Medicine, Hokkaido, Japan. yamakage@sapmed.ac.jp
Kamada
Y
Y
Toriyabe
M
M
Honma
Y
Y
Namiki
A
A
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*
D006993:Hypnotics and Sedatives; D002245:Carbon Dioxide; D008874:Midazolam; D010100:Oxygen; D015742:Propofol