Causation Not Correlation: Simple Mediation Analysis of Amputation Costs.

Introduction: The COVID-19 pandemic significantly impacted health-care delivery and hospital financials. This study aims to identify the pandemic's effects on costs associated with nonelective major lower extremity amputation (LEA) and mediating factors influencing this cost.

Methods: The 2019-2021 Florida Agency for Health Care Administration database was queried for adult patients who underwent nonelective LEA. Patient inflation-adjusted costs were collected. Florida COVID-19 mortality rates established 9-month COVID-heavy (CH) and COVID-light (CL) timeframes, compared to a 9-month pre-COVID (PC; 2019) timeframe. Simple mediation analysis with 2000 bootstrapping interactions evaluated patient comorbidity, surgical complications, and hospital treatment factors as potential mediators on cost.

Results: A total of 5963 patients were included (1957 PC, 1994 CH, 2012 CL). Compared to PC, COVID timeframes had significantly increased total (+7.8%), hospital (+14.5%), intensive care unit (+14.3%), and operating room (+14.9%) costs. Simple mediation analysis identified potential influencers of increased cost: (1) acute kidney injury during CL (P = 0.03), (2) sepsis during CL (P = 0.02), and (3) electrolyte/acid-base disorders during CH and CL (P < 0.01). Sensitivity analysis (E-values) could not exclude unmeasured confounding from the model findings.

Conclusions: The COVID-19 pandemic led to substantial cost increases associated with nonelective major LEAs, but simple mediation analysis did not identify sensitive mediators to cost. This suggests systemic factors, such as supply chain disruptions and staffing shortages, may warrant investigation. The pandemic highlighted the need for resilient health-care systems that can address both acute and chronic care needs while mitigating inequities exacerbated by crises.