Respiratory effects of intravenous midazolam.

Thirty-four healthy, young-adult patients receiving intravenous midazolam for third-molar surgery had their respiratory parameters measured by respiratory inductive plethysmography. Tidal volume and minute volume showed significant changes during the initial 5-10 minutes of sedation, the changes being maximal during the first 5 minutes from the completion of injection of midazolam. The measurement of phase angle, an indicator of respiratory asynchrony, showed no significant change from normal, although a few patients showed some asynchrony of breathing, suggesting some amount of respiratory obstruction. A few patients showed a short period of apnoea and a small fall in the oxygen saturation. None of these changes caused any clinical concerns. It is suggested that the absence of stimulation after injection of midazolam, particularly in the initial few minutes, may contribute to the potential onset of respiratory problems.