Variation in Hospital Length of Stay Based on Hospital Volume: A RetrospectiveCohort Study of Emergency Abdominal Surgery in Ireland

Objectives: Emergency abdominal surgery (EAS) refers to high risk intra-abdominal surgical procedures associated with increased mortality risk and long length of hospital stay. The variation between hospital volume and hospital length of stay (LOS) of patients undergoing EAS is poorly understood. Our objective was to explore this relationship across public hospitals in Ireland. Methods: Data for all adult episode discharges from public Irish hospitals in 2014-2017 were obtained from National Quality Assurance Improvement System (NQAIS) Clinical with EAS identified by primary procedure codes. Hospitals were categorised into low (n<200), medium (n=200-400), and high (n>400) volume groups based on the number of EAS episodes during the study period. Negative binomial regression models were applied to standardise for patient case mix. Several adjusted LOS measures were compared across the three volume groups. Sensitivity analysis was conducted to test the robustness of our findings. Results: 8120 hospital episodes across 24 public hospitals providing EAS services were analysed. 7 were categorised as low, 9 as medium, and 8 as high-volume hospitals. High volume hospitals had a significantly longer adjusted LOS (24.7 days) relative to low and medium volume hospitals (18.2 and 18.6 days). Sensitivity analysis consisted of the exclusion of the following hospital episodes: in-hospital death, cancer diagnosis, Charlson comorbidity index (CCI) >0, admission from other hospitals, and discharge to other hospitals. No single variable influenced the observed LOS variation, although when the more complex episodes were excluded, the post-operative LOS at low and medium volume hospitals was significantly shorter compared to high volume hospitals (by 1.1-6.1 days). Intensive care unit (ICU) LOS was similar in all three hospital volume groups although low volume hospitals appeared to have more ICU admissions and longer stay (by up to 1.6 days). Conclusions: Our findings indicate that patients treated at low volume hospitals have shorter LOS and may be discharged earlier than from high volume hospitals. This finding is surprising, suggesting that concentration of services to larger clinical departments may not necessarily reduce LOS and improve the efficiency of resource utilisation and service delivery.