Equal Ratio Ventilation Reduces Blood Loss During Posterior Lumbar Interbody Fusion Surgery

Study Design. A prospective randomized double-blinded study. Objective. The aim of this study was to compare the effect of two different ventilator modes (inspiratory to expiratory ratio [I:E ratio] of 1:1 and 1:2) on intraoperative surgical bleeding in patients undergoing posterior lumbar interbody fusion (PLIF) surgery. Summary of Background Data. During PLIF surgery, a considerable amount of blood loss is anticipated. In the prone position, engorgement of the vertebral vein increases surgical bleeding. We hypothesized that equal ratio ventilation (ERV) with I:E ratio of 1:1 would lower peak inspiratory pressure (PIP) in the prone position and consequentially decrease surgical bleeding. Methods. Twenty-eight patients were randomly assigned to receive either ERV (ERV group, n = 14) or conventional ventilation with I:E ratio of 1:2 (control group, n = 14). Hemodynamic and respiratory parameters were measured at 5 minutes after anesthesia induction, at 5 minutes after the prone position, at the time of skin closure, and at 5 minutes after turning to the supine position. Results. The amount of intraoperative surgical bleeding in the ERV group was significantly less than that in the control group (975.7 +/- 349.9mL vs. 1757.1 +/- 1172.7 mL, P = 0.030). Among other hemodynamic and respiratory parameters, PIP and plateau inspiratory pressure (P-plat) were significantly lower and dynamic lung compliance (C-dyn) was significantly higher in the ERV group than those of the control group throughout the study period, respectively (all P< 0.05). Conclusion. Compared to conventional ratio ventilation, ERV provided lower PIP and reduced intraoperative surgical blood loss in patients undergoing PLIF surgery.