Intra-Operative Hypotension is an Important Modifiable Risk Factor for Major Complications in Spinal Fusion Surgery

Study Design: Retrospective observational cohort Objectives: This study explores the impact of Intraoperative hypotension (IOH)on post-op complications for major thoracolumbar spine fusion procedures. Summary of Background Data: IOH with mean arterial pressure (MAP) < 65 mmHg is associated with post-op acute kidney injury (AKI) in general surgery. In spinal deformity surgery, IOH is a contributing factor to MEP changes and spinal cord dysfunction with deformity correction. Methods: 539 thoracolumbar fusion cases, > 6 surgical levels and > 3 hours duration were identified. Anesthetic/surgical data included OR time, fluid volume, blood loss, blood product replacement and use of vasopressors. Arterial-line based MAP data was collected at 1 min intervals. Cummulative duration of MAP < 65 mmHg was recorded. IOH within the first hour of surgery vs. the entire case was determined. Post-op course and complications including SSI, GI complications, pulmonary complications, MI, DVT, PE, AKI and encephalopathy were noted. Cumulative complications were grouped as none, 1-2 complications, or >3 complications. Results: There was a significant association between occurrence of complications and duration of IOH within the first hour of surgery (8.2 vs. 5.6 min, P <0.001) and across the entire procedure (28.1 vs. 19.3 min, P =0.008). This association persisted for individual major complications including SSI, acute respiratory failure, PE, ileus requiring NGT and post-operative cognitive dysfunction. Comparison of patients with 0 vs. 1-2 vs. 3 or more complications demonstrated that patients with 3 or more complications had a longer duration of IOH in the first hour of the surgery and that patients who had no complications received less vasopressor than patients who had 1-2 or 3 or more complications. Conclusion: This study identifies duration of IOH during the first hour of surgery as a previously unrecognized modifiable risk associated with major complications for multi-level lumbar fusion surgery.