Increase in Airway Pressure Resulting From Prone Position Patient Placing May Predict Intraoperative Surgical Blood Loss

In Brief Study Design. Prospective study on intraoperative blood loss during lumbar spine surgery. Objective. To evaluate the relationship between airway pressure change due to the patient's prone position and intraoperative blood loss during lumbar spine surgery. Summary of Background Data. A prone position may increase abdominal pressure. Changes in abdominal pressure may influence airway pressure and cause intraoperative blood loss as a result of epidural venous congestion. Methods. Patients undergoing lumbar spine surgery were placed in a prone position after the administration of general anesthesia. Peak airway pressure, plateau pressure, mean blood pressure, and heart rate were measured 5 minutes after anesthesia induction and 15 minutes after being placed in a prone position. Intraoperative blood loss was measured at the end of surgery. Results. Mean peak airway pressure was 13.7 ± 1.8 mm Hg while in a supine position and increased to 15.1 ± 2.5 mm Hg after placement in the prone position (P = 0.002). Plateau pressure was 12.6 ± 2.5 mm Hg while in a supine position and increased to 14.1 ± 1.9 mm Hg after placement in a prone position (P = 0.0002). Intraoperative blood loss was correlated with peak (R2= 0.405) and plateau (R2= 0.489) airway pressure changes. Conclusion. Increase in airway pressure resulting from placement into a prone position may predict intraoperative surgical blood loss. During lumbar spine surgery, intraoperative blood loss increased in association with increases in peak and plateau airway pressure change as a result of shifting the patient from a supine to a prone position. If peak and plateau airway pressures increase as a result of shifting into a prone position, it is predicted that there will be an increase in intraoperative blood loss.