A National Evaluation of Ambulatory Surgery Utilization Among Emergency General Surgery and Trauma Patients

Introduction: Ambulatory Surgery Centers (ASCs) are increasingly prevalent in the United States. Acute Care Surgery (ACS) patients — defined as emergency general surgery (EGS) and trauma patients — comprise 20% of the inpatient population and 25% of total inpatient costs, but the volume of outpatient ACS procedures has not been characterized. We quantified the national burden and costs of ACS procedures occurring in ASCs. Methods: We queried the 2017 Nationwide Ambulatory Surgery Sample (NASS), a newly-released national all-payer ambulatory surgery database. We included patients ≥18 years with EGS or trauma as defined by the International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) codes. The primary outcome was total charges;the secondary outcome was discharge disposition. Results: Among 9 million ambulatory surgery patients, 772,484 (8.2%) had an EGS diagnosis and 1,073,734 (11.4%) had a trauma diagnosis. Total costs for ACS patients were $38.3 billion, or 18.0% of outpatient surgical costs. EGS patients had higher rates of routine discharge home than trauma patients (99.4% vs. 98.0%, p<0.001);remaining patients required transfer to inpatient hospitals. Patients most likely to be discharged home included those with cholecystitis (aOR 3.7), hernia surgery (aOR 4.4), self-pay patients (aOR 2.1), and those treated at urban hospitals (aOR 1.6) (p<0.001). Conclusion: ACS patients comprise 20% of the outpatient surgical population and 18% of ASC costs. The growing importance of ASCs is highlighted by the COVID-19 pandemic, suggesting an opportunity to conserve inpatient resources and relocate additional ACS procedures to the outpatient setting.