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Respiratory interaction after spinal anesthesia and sedation with midazolam
R A Gauthier1, B Dyck, F Chung
1Department of Anesthesia, University of Toronto, Toronto Hospital, Canada.
Anesthesiology
|November 1, 1992
Summary
Intravenous midazolam depresses resting ventilation, while spinal anesthesia stimulates it. Their combination synergistically depresses ventilation more than expected, impacting respiratory responses.
Area of Science:
- Anesthesiology
- Respiratory Physiology
Background:
- Midazolam and spinal anesthesia are frequently used together in clinical settings.
- The individual effects of midazolam and spinal anesthesia on ventilation are known, but their combined impact remains unexamined.
Purpose of the Study:
- To investigate the effects of intravenous midazolam, spinal anesthesia, and their combination on resting ventilation and ventilatory responses to hypercapnia.
Main Methods:
- Nineteen healthy volunteers participated in the study.
- Ventilation was assessed under conditions of intravenous midazolam (0.05 or 0.075 mg/kg), spinal anesthesia (T3-T8), and their combination.
- Ventilatory responses to progressive hyperoxic hypercapnia were measured.
Main Results:
- Midazolam decreased tidal volume and inspiratory flow rate, while increasing respiratory frequency.
- Spinal anesthesia increased tidal volume, inspiratory flow rate, and minute ventilation, while decreasing respiratory frequency.
- The combination of midazolam and spinal anesthesia resulted in a synergistic decrease in minute ventilation, tidal volume, and inspiratory flow rate, exceeding the sum of individual effects.
Conclusions:
- Intravenous midazolam depresses resting ventilation.
- Spinal anesthesia stimulates resting ventilation.
- The combination of midazolam and spinal anesthesia exerts a modest synergistic effect in depressing resting ventilation.