Predictors and Outcomes of Acute Respiratory Failure in hospitalized Acute Pancreatitis Patients
This is a retrospective cohort study using the Nationwide Inpatient Sample (NIS) database from the year 2005 to 2014. The NIS is the largest publicly available all-payer inpatient database in the United States, which contains data from up to 46 participating States comprising of almost 1,000 hospitals. It consists of 20% stratified sample of all discharges from the participating hospitals and contains data on more than 8 million discharges per year. Each discharge is treated as a unique entry and is coded with one primary discharge diagnosis and up to 25 secondary diagnoses as well as 15 associated procedures coded using the International Classification of Diseases, Clinical Modification, ninth edition (ICD-9-CM Codes). The NIS is maintained as part of the Healthcare Cost and Utilization Project of the Agency for Healthcare Research and Quality.
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The study population consisted of all hospitalizations with a primary or secondary discharge diagnosis of AP using the ICD-9-CM code 577.0 . Those who had a primary or secondary discharge diagnosis of ARF were identified through querying the ICD-9 CM codes 518.5, 518.81, or 518.82. Patients who had continuous invasive mechanical ventilation were identified with the ICD-9-CM coded 96.70, 96.71 or 96.72 .Patients who were below the age of 18 years, had missing hospital mortality data, those with history of chronic pancreatitis and pancreatic cancer were excluded. Our primary population of interest was patients who had concomitant diagnosis codes for both AP and ARF (AP-ARF group). The AP patients without ARF formed the control group. The primary outcome measures include in hospital mortality and the secondary outcomes are hospital length of stay and hospitalization cost. The NIS database contains patient characteristics including age, gender, race and insurance type. The hospital characteristics included hospital region, teaching status, number of hospital beds, and hospital location. The information on race was missing in 14% of the patients and was treated as a separate category. Comorbidity risk adjustment was done using the Agency for Healthcare Research and Quality (AHRQ) comorbidity measures based on the methods by Elixhauser et al. Patients were given a score of less than 3 or greater than 3, based on the number of comorbidities. Complications associated with AP were also analyzed using appropriate ICD-9-CM codes and included ARF, cardiac failure, renal failure, hepatic failure and hematological complications. We identified cases of ARF using the ICD-9-CM codes 518.5, 518.81 and 518.82, which were validated in previous studies. To define acute respiratory distress syndrome (ARDS) we used Thomsen and Morris ARDS criteria. Patients who needed mechanical ventilation where identified using the procedural codes 96.70, 96.71, and 96.72.