Changes in oxygen supply-demand balance during induction of general anesthesia: an exploratory study using remimazolam.

Purpose: This study was performed to evaluate the changes in oxygen supply-demand balance during induction of general anesthesia using an indirect calorimeter capable of measuring oxygen consumption (VO₂) and carbon dioxide production (VCO₂).

Methods: This study included patients scheduled for surgery in whom remimazolam was administered as a general anesthetic. VO₂ and VCO₂ were measured at different intervals: upon awakening (T1), 15 min after tracheal intubation (T2), and 1 h after T2 (T3). Oxygen delivery (DO₂) was calculated simultaneously with these measurements. VO₂ was ascertained using an indirect calorimeter and further calculated using vital signs, among other factors. DO₂ was derived from cardiac output and arterial blood gas analysis performed with an arterial pressure-based cardiac output measurement system.

Results: VO₂, VCO₂, and DO₂ decreased significantly from T1 to T2 and T3 [VO₂/body surface area (BSA) (ml/min/m²): T1, 130 (122-146); T2, 107 (83-139); T3, 97 (93-121); p = 0.011], [VCO₂/BSA (ml/min/m²): T1, 115 (105-129); T2, 90 (71-107); T3, 81 (69-101); p = 0.011], [DO₂/BSA (ml/min/m²): T1, 467 (395-582); T2, 347 (286-392); T3, 382 (238-414); p = 0.0020]. Among the study subjects, a subset exhibited minimal reduction in VCO₂. Although the respiratory frequency was titrated on the basis of end-tidal CO₂ levels, there was no significant difference between the groups.

Conclusion: General anesthetic induction with remimazolam decreased VO₂, VCO₂, and DO₂.