Hospital characteristics; geographical region, teaching status and size of hospitals included in this study
| Hospital characteristic | Clinical outcomes analysis |
| Geographical region | |
| Northeast | 1 |
| South | 3 |
| Midwest | 1 |
| West | 4 |
| Teaching status | |
| Teaching | 7 |
| Non-teaching | 2 |
| Hospital Size | |
| Small (<100 beds) | 3 |
| Medium (100–250 beds) | 2 |
| Large (>250 beds) | 4 |