Data Source
Institutional review board approval was not needed, as all patient information is de-identified within the NIS, and informed consent was waived. The National Inpatient Sample (NIS) offers the largest database of hospitalizations, representing a 20% random, stratified, sample of hospital discharges in the United States. To identify the study population, International Classification of Diseases, ninth (ICD-9) and tenth (ICD-10) revisions, Clinical Modification (CM) and Procedure Coding System (PCS) codes were used.