National hospital volume in acute pancreatitis: analysis of the Nationwide Inpatient Sample 1998-2006

Background: The optimal management of acute pancreatitis remains controversial and current treatment protocols vary in degrees of medical and surgical management. Our group has previously shown in population-based studies that high-volume (HV) hospitals have lower rates of in-hospital mortality after pancreatectomy. We sought to examine if a similar mortality benefit exists for patients admitted with acute pancreatitis. Methods: Using the Nationwide Inpatient Sample (NIS), we examined discharge records for all adult admissions during 1998-2006 with a primary diagnosis of acute pancreatitis of any aetiology. Unique hospital identifiers were used to divide hospital volumes into equal thirds based on the number of admissions for acute pancreatitis per year (lowest tertile [low volume, LV] <= 64 admissions/year; medium tertile [medium volume, MV] 65-117 admissions/year; highest tertile [high volume, HV] >= 118 admissions/year). Covariates included patient demographics, hospital characteristics and patient co-morbidities using the Elixhauser index. Adjusted mortality represented the primary outcome measure and adjusted length of stay (LOS) and total charges were considered secondary measures. Results: There were 416 489 primary admissions for acute pancreatitis during the study period. In-hospital mortality for the cohort amounted to 1.6% (n = 6446). Hospital admissions for acute pancreatitis increased over the study period (P < 0.0001). High-volume hospitals tended to be large (82%), urban (99%) teaching (59%) centres (P < 0.0001), which cared for patients with more co-morbidities (35.9% of patients at HV hospitals vs. 29.1% at LV hospitals had at least three co-morbidities; P < 0.0001). Low-volume centres appeared more likely to perform pancreatic procedures than HV hospitals (odds ratio [OR] 1.50, 95% confidence interval [CI] 1.32-1.70). Patients at HV hospitals had a lower likelihood of a prolonged adjusted LOS compared with those at LV (OR 0.75, 95% CI 0.71-0.79) or MV (OR 0.82, 95% CI 0.79-0.85) hospitals. After adjusting for patient and hospital factors, there was an in-hospital mortality benefit associated with being treated at an HV centre (OR 0.70, 95% CI 0.63-0.77). The decision to operate on a given patient did not alter the mortality benefit of the HV hospital. Conclusions: Rates of admissions for acute pancreatitis in the USA are increasing. High annual hospital volume of acute pancreatitis cases confers a shorter LOS, lower adjusted mortality and a lower likelihood of pancreatic procedure for patients admitted with acute pancreatitis. Although HV hospitals were less likely than MV or LV centres to perform pancreatic procedures, the role of surgery remains unclear. Further studies should examine other possible reasons for this mortality benefit, such as the availability of specialists, the quality of critical care facilities and the timing of operative intervention.