Ventilation Mode and Epidural Bleeding in Microdiscectomy: Comparison of Two Ventilation Techniques

Two different ventilation protocols during general anesthesia have been compared regarding their effects on amount of epidural bleeding during lumbar microdiscectomy in the prone position. Previous studies have not not revealed a relationship between ventilation mode and epidural bleeding in the prone position while measuring the intra-abdominal pressure (IAP) level. This study was conducted on 40 American Society of Anesthesiologists (ASA) I and II patients that underwent a single level, unilateral lumbar microdiscectomy in the prone position. The anesthetic protocol was the same except the ventilation modes that were used in the study: (1) high volume-low frequency technique in group A, and (2) low volume-high frequency technique in group B. Pulmonary and hemodynamic parameters were noted. The patients also had urinary bladder catheter to measure the intra-abdominal pressure during surgery. Epidural bleeding was measured in every patient after microdiscectomy by using the aspiration volume. A convenience scale was used to assess the surgeon's satisfaction. Although intra-abdominal pressure remained within normal ranges in both groups, peak and plateau pressures were slightly higher in group A. Mean epidural bleeding after ligamentum flavum resection was 43.9 ± 11.82 ml in group A, and 26.35 ± 6.59 ml in group B. The difference was statistically significant. Also the surgeon's satisfaction according to convenience scale was better in group B. Decreasing epidural venous engorgement depends on the ventilation technique and may lead to surgical convenience. It may be suggested that high frequency-low tidal volume ventilation during general anesthesia for lumbar microdiscectomy can be useful in minimizing epidural bleeding by using low peak and plateau pressure during surgery.