Risk Factors for Post-Operative Cognitive Dysfunction Following Multilevel Lumbar Spinal Fusion

Introduction: Post-Operative Cognitive Dysfunction (POCD) is a serious, common and under-recognized complication in elderly patients undergoing surgery. Risk factors for POCD vary in the literature and include preoperative as well as intraoperative factors. This study examines risk factors for POCD following multilevel lumbar fusion.

Methods: A retrospective cohort of 566 thoracolumbar fusion cases with a minimum of 4 surgical levels were identified. Chart review was performed for occurrence of POCD and known risk factors for POCD. Anesthetic and surgical data included OR time, fluid volume, blood loss, blood product replacement and use of vasopressors. Arterial line based mean arterial pressure (MAP) data was collected at 1-minute intervals and cumulative duration of MAP < 65mmHg was recorded. Univariate and multivariate statistical analysis was used to investigate the relationship between demographic, preoperative and intraoperative risk factors and the occurrence of POCD.

Results: Overall, 70 out of 566 patients (12.4%) experienced POCD described most commonly as Encephalopathy (57, 81%), Delirium (8, 11%), Hallucinations (3, 4%) and Altered Mental Status (2, 3%). Patients who developed POCD were older (68.7yrs vs 59.6yrs, p< 0.001), had a worse ASA scores (2.9 vs 2.7, p=0.004), more obesity related comorbidities with a higher BMI (32.0 vs 30.0p=.007), a higher incidence of diabetes (31% vs 16%, p=.002), and sleep apnea (47% vs 28%, p=0.002).
Intraoperatively patients who experienced POCD had greater fluid shifts and hemodynamic instability in terms of blood loss (800cc vs 660cc, p=0.047), blood transfusion (350cc vs 201cc, p=0.014), minutes of intraoperative hypotension (11.6 vs 6.4, p=0.043) and vasopressor use (10604mcg vs 6823mcg, p=0.029).

Conclusion : Post-Operative Cognitive Dysfunction is associated with age, preoperative comorbidities and greater intraoperative hemodynamic instability. These factors present targets for optimization prior to surgery to lower the incidence of Post-Operative Cognitive Dysfunction.