Lumbar Microdiscectomy With Spinal Anesthesia Comparison of Prone and Knee-Chest Positions in Means of Hemodynamic and Respiratory Function

Study Design. Prospective clinical study to compare the physiologic changes in lumbar disc surgery regarding to positions. Objective. To compare the perioperative hemodynamic and respiratory functions between prone and knee-chest positions for lumbar disc surgery under spinal anesthesia. Summary of Background Data. Spinal anesthesia is a safe but rarely used alternative to general anesthesia for lumbar disc surgery. It reduces blood loss, avoid pressure necrosis, and nerve injuries, and it provides a more comfortable postoperative period. Prone and knee-chest positions are mostly used positions in lumbar discectomy; hemodynamic and respiratory effects of spinal anesthesia and the differences between these 2 positions in spinal anesthesia were evaluated in this study, which only been evaluated in general anesthesia. Methods. Forty-five patients were randomized for lumbar microdiscectomy with spinal anesthesia under either prone position (group 1 n = 22) or knee-chest position (group 2 n = 23). All patients were classified as physical status 1 or 2 according to the American Association of Anesthesiology. Spinal anesthesia was performed with hyperbaric bupivacaine. Perioperative continuous hemodynamics and respiratory function test results were recorded after the spinal anesthesia was performed. Results. Immediately after the spinal anesthesia was performed, both the systolic and diastolic arterial blood pressure values were significantly decreased and heart rates were significantly increased in both groups. Both positions showed significant decrease in forced vital capacity (P = 0.002) and forced expiratory volume in 1 second (P = 0.0015) during the surgery respect to preoperative values. The decrease in peak expiratory flow (P = 0.011) and forced expiratory flow at the 25% of the pulmonary volume (P = 0.011) was significant in kneechest position respect to prone position. Conclusion. In conclusion, spinal anesthesia is appropriate for lumbar disc surgery with respect to the hemodynamic parameters in both prone and knee-chest positions, however, in terms of pulmonary functions, the knee-chest position can cause a restrictive effect. Therefore this position should be used cautiously in higher-risk patients.