2008 Annual Meeting Abstracts

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Although center volume has been shown to be important in improved outcomes after liver resection (LR), the relationship of surgeon to center volume remains unclear. In a case controlled analysis, we attempted to determine if volume (surgeon or center) truly affects survival in LR after eliminating differences in background characteristics.
Methods: We used the Nationwide Inpatient Sample (NIS) to identify all LRs with available surgeon/hospital identifiers performed from 1998-2005. High volume (HV) hospitals were defined as >=20 LR/yr and HV surgeons performed >=10 LR/yr. Preoperative comorbidities were assessed with the Elixhauser index. Incorporating patient and hospital factors, we used propensity scoring to adjust for background characteristics and create matched controls of low volume (LV) and HV hospitals. A logistic regression for mortality was then performed with these matched groups. To assess the relationship of surgeon and hospital volume, different combinations of HV and low volume (LV) surgeons and hospitals were grouped and assessed separately.
Results: 3032 LRs were performed in the 8-year period. Compared to LV centers (n=1504), patients treated at HV hospitals (n=1528) were more often white (75% vs. 70%) than black (7% vs. 12%), private insurance holders (56% vs. 48%), elective admissions (93% vs. 78%) and high income residents (42% vs. 34%) (p< 0.005). Unadjusted in-hospital mortality was significantly lower in the HV group (6% vs. 3%, p <0.001). Propensity matching successfully eliminated differences in background characteristics between HV and LV hospitals. Logistic regression found that factors that significantly decreased risk of in-hospital mortality after LR were private insurance (OR 0.4, 95% CI 0.2-0.8) and elective admission type (OR 0.3, 95% CI 0.1-0.7); preoperative comorbidity increased risk of death. Patients treated by HV surgeons or centers alone did not achieve a survival benefit after adjustment of patient and hospital factors. Only LR performed by HV surgeons at HV centers was independently associated with improved in-hospital mortality (OR 0.5, 95% CI 0.3-0.8).
Conclusions: Our results confirm that a socioeconomic bias (race, insurance, income) may exist at HV centers. When these factors are accounted for and adjusted, center volume does not appear to influence in-hospital mortality unless LR are performed by HV surgeons at HV centers.

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