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

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).

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.

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.

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