Introduction
lung injury, bleeding, intraoperative blood loss, inferior vena cava
SURGICAL BLOOD LOSS, BLEEDING, OBESE, INTRAOPERATIVE BLOOD LOSS
Demand for lumbar spine fusion, a common surgical procedure used for the treatment of many spinal conditions, has been increased in recent decades [Reduction of surgical blood loss is crucial to maintain hemodynamic stability and the desirability of the surgical field. Meanwhile, convenience of the surgeon is associated with reduction of intraoperative blood loss due to reduced operation time [Volume-controlled ventilation (VCV), which is known as the classic ventilation mode, has been used for decades with a constant flow to deliver a target tidal volume and thus ensure satisfactory minute ventilation; however, using VCV mode may result in high airway pressure levels when chest compliance decreased, such as in obese patients, and lead to ventilation induced lung injury [Although there are no remarkable differences between the two ventilation modes, some researchers have carefully recommended changing the ventilation settings from VCV to PCV in some situations [Surgical bleeding in prone position has been known to be associated with increase in intra-abdominal pressure (IAP), peak inspiratory pressure (PIP), and inferior vena cava (IVC) compression. Therefore, reduction of IAP, PIP, and IVC have been suggested to control intraoperative surgical blood loss. Some authors argued that PCV by providing lower PIP, compared with VCV, may be useful in control of surgical bleeding [With regard to bleeding outcome, some studies have particularly shown that using PCV can reduce intraoperative blood loss [Considering the above-mentioned controversies, we carried out the present study to investigate the effect of mechanical ventilation mode on the outcomes in patients undergoing posterior lumbar inter-body fusion (PLIF) in prone position. To reach this goal, we compared VCV and PCV in terms of surgical outcomes. Our primary outcome was the amount of intraoperative blood loss. Secondary outcomes were heart rate, blood pressure, transfusion requirement, and surgeon satisfaction.