Comparison of metabolic flow with low-flow anesthesia technique using sevoflurane on pulmonary mechanics in...

Previous studies found that low-flow sevoflurane anesthesia in respiratory mechanics is comparable with higher flow during laparoscopic surgery, but metabolic flow has not been studied adequately. The study compares the effect of metabolic flow with the low-flow technique on respiratory mechanics during laparoscopic procedures.

Sixty adult patients of either sex, American Society of Anesthesiologists physical status I-II scheduled for laparoscopic surgery of <3 h were randomly assigned into group M: metabolic (n = 30) and group L: low-flow anesthesia (n = 30). Both groups received fresh gas flow (FGF) of 6 L/min of oxygen, air, and sevoflurane until they attained a minimum alveolar concentration (MAC) of 1; FGF was changed to 1 L/min in group L. In group M, the FGF was changed to estimate the metabolic flow of oxygen (Brody's formula) plus the leak detected during the pre-use check. The delivered FiO₂ was maintained above 50%, and The dial concentration of sevoflurane was adjusted to maintain a target MAC-1 throughout the procedure in both groups. The primary objective was to compare postoperative forced vital capacity (FVC) after achieving a Modified Aldrete Score of ≥9. The secondary objectives included comparing arterial blood gas (ABG) parameters, hemodynamic parameters, and sevoflurane consumption.

There was no statistically significant difference in the FVC, ABG, and hemodynamic parameters between the two groups pre- (T1) and postoperatively (T2, T3, T4). There was a statistically significant decrease in sevoflurane consumption (P = <0.001) in the metabolic-flow group.

The effects of metabolic-flow anesthesia on pulmonary mechanics and gas exchange were similar to those of the low-flow anesthesia technique.