Select patient and operative characteristics by site
| Variable | Hospital A | Hospital B | Hospital C | All patients | P value |
| No. of patients | 6719 | 8892 | 7829 | 23 440 | |
| Emergency case, % | 17.7% | 13.2% | 9.3% | 13.2% | <0.001 |
| Outpatient surgery, % | 35.7% | 32.7% | 20.1% | 29.4% | <0.001 |
| Mean primary procedure work relative value units (RVUs) (SD) | 17.3 (8.5) | 15.2 (7.6) | 16.1 (8.5) | 16.2 (8.2) | <0.001 |
| Patient’s age≤40 years | 24.5% | 22.5% | 17.2% | 21.3% | <0.001 |
| Patient’s age >70 years | 13.3% | 14.3% | 21.5% | 16.4% | |
| Male, % | 43.0% | 43.7% | 39.3% | 42.0% | <0.001 |
| Minority race, % | 8.6% | 13.0% | 23.4% | 15.2% | <0.001 |
| ASA class III | 51.1% | 52.7% | 42.7% | 48.9% | <0.001 |
| ASA class IV–V | 6.0% | 4.4% | 4.3% | 4.8% | |
| HCT >38% | 68.2% | 67.6% | 69.2% | 68.3% | <0.001 |
| HCT 35.1%–38% | 12.9% | 14.6% | 15.0% | 14.2% | |
| HCT≤35% | 18.9% | 17.8% | 15.8% | 17.5% |
ASA, American Society of Anesthesiologists; HCT, hematocrit.