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Introduction
Sepsis is the 10th most common cause of death in the United States [1] . The incidence of sepsis and the number of sepsis-related deaths are increasing [2] . In addition, sepsis is a huge economic burden with an annual cost of US $16.7 billion nationally [3] . Acute kidney injury (AKI) develops in around 15% of patients requiring hospitalizations [4] . Its incidence is even more common in septic patients, with nearly 20% of even moderate sepsis being complicated by AKI [5] . Sepsis has been established as one of the most common causes of AKI in critically ill patients with associated increased in-hospital mortality and longer duration of hospital and intensive care unit stay [6] . The most severe form of AKI, that requiring dialysis (AKI-D), has an even worse prognosis with mortality rates approaching 50% [7] . Although AKI frequently occurs in septicemia and is associated with worse prognosis, the impact of AKI-D has not been thoroughly elucidated. We explored the epidemiology of AKI-D in septicemia using data from a large, nationally representative database.
Methods and statistical analysis
We used the National Inpatient Sample database from 2002 to 2013 to identify adults hospitalized with septicemia using Clinical Classification Software developed by the Agency for Healthcare Research and Quality. We defined AKI using International Classification of Diseases, Ninth Revision, Clinical Modification, code 584.xx and dialysis by procedure code of 39.95 or diagnoses code of v45.11, v56.0, or v56.1. To avoid misclassification of hospitalizations for chronic hemodialysis, we excluded those with procedure codes for arteriovenous access creation/revision [8] . We excluded hospitalizations with dialysis codes but no AKI code, assuming that patients were receiving dialysis for end-stage renal disease. This approach has been used previously and has high sensitivity and specificity [9] . We used SAS 9.3 (SAS Institute Inc, Cary, NC) for all analyses.
Results
From 2002 to 2013, we had a national estimate of 8 108 048 hospitalizations with septicemia, of which 214 185 (2.64%) had AKI-D. There was a substantial increase in the proportion of AKI-D in septicemia hospitalizations, from 1.4% in 2002 to 2.65% in 2013 (Fig. 1 ). Persons with AKI-D were younger (mean age 64.49 vs 68.86 years; P<.0001) and were more likely to be...