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

Abstract

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.