Patient demographics, preoperative and operative variables
| Variable | Unmatched | Matched | ||||
| General anesthesia (n=1 49 996) | Regional anesthesia (n=1014) | SMD* | General anesthesia (n=3042) | Regional anesthesia (n=1014) | SMD* | |
| Demographics | ||||||
| Age, mean (SD) | 57.54 (15.8) | 53.45 (16.2) | 0.257 | 53.45 (16.1) | 53.45 (16.2) | 0.000 |
| Female sex, n (%) | 65 506 (43.7) | 433 (42.7) | 0.020 | 1307 (43.0) | 433 (42.7) | 0.005 |
| Race, n (%) | ||||||
| White | 118 867 (79.2) | 844 (83.2) | 0.102 | 2478 (81.5) | 844 (83.2) | 0.047 |
| African American | 10 441 (7.0) | 41 (4.0) | 0.128 | 197 (6.5) | 41 (4.0) | 0.109 |
| Other | 4636 (3.1) | 46 (4.5) | 0.076 | 73 (2.4) | 46 (4.5) | 0.117 |
| Unknown | 16 052 (10.7) | 83 (8.2) | 0.086 | 294 (9.7) | 83 (8.2) | 0.052 |
| BMI, mean (SD) | 30.58 (6.47) | 29.48 (6.07) | 0.175 | 29.22 (5.96) | 29.48 (6.07) | 0.044 |
| BMI, median (range) | 29.7 (10.0–168.1) | 28.6 (18.0–65.5) | N/A | 28.3 (16.0–68.6) | 28.5 (18.0–65.5) | N/A |
| Preoperative variables | ||||||
| Functional status (dependent), n (%) | 2334 (1.6) | 3 (0.3) | 0.132 | 33 (1.1) | 3 (0.3) | 0.095 |
| Outpatient, n (%) | 76 286 (50.9) | 722 (71.2) | 0.426 | 2159 (71.0) | 722 (71.2) | 0.005 |
| Smoker within 1 year, n (%) | 29 535 (19.7) | 184 (18.1) | 0.039 | 639 (21.0) | 184 (18.1) | 0.072 |
| Steroid use, n (%) | 5777 (3.9) | 33 (3.3) | 0.032 | 107 (3.5) | 33 (3.3) | 0.015 |
| Weight loss, n (%) | 353 (0.2) | 3 (0.3) | 0.012 | 5 (0.2) | 3 (0.3) | 0.027 |
| Diabetes, n (%) | 25 994 (17.3) | 118 (11.6) | 0.162 | 408 (13.4) | 118 (11.6) | 0.054 |
| Dyspnea, n (%) | 6260 (4.2) | 21 (2.1) | 0.121 | 106 (3.5) | 21 (2.1) | 0.086 |
| COPD, n (%) | 5259 (3.5) | 25 (2.5) | 0.061 | 75 (2.5) | 25 (2.5) | 0.000 |
| Heart failure, n (%) | 411 (0.3) | 0 (0.0) | 0.074 | 6 (0.2) | 0 (0.0) | 0.063 |
| Hypertension, n (%) | 74 175 (49.5) | 398 (39.3) | 0.206 | 1207 (39.7) | 398 (39.3) | 0.009 |
| Dialysis, n (%) | 313 (0.2) | 3 (0.3) | 0.017 | 3 (0.1) | 3 (0.3) | 0.044 |
| Disseminated cancer, n (%) | 444 (0.3) | 1 (0.1) | 0.044 | 5 (0.2) | 1 (0.1) | 0.018 |
| Bleeding disorder, n (%) | 2126 (1.4) | 11 (1.1) | 0.030 | 27 (0.9) | 11 (1.1) | 0.020 |
| Open wound/wound infection, n (%) | 481 (0.3) | 2 (0.2) | 0.024 | 7 (0.2) | 2 (0.2) | 0.007 |
| Preoperative blood transfusion, n (%) | 123 (0.1) | 0 (0.0) | 0.041 | 1 (0.0) | 0 (0.0) | 0.026 |
| Operative variables | ||||||
| ASA class, n (%) | ||||||
| 1 | 9764 (6.5) | 123 (12.1) | 0.194 | 382 (12.6) | 123 (12.1) | 0.013 |
| 2 | 77 111 (51.4) | 607 (59.9) | 0.171 | 1779 (58.5) | 607 (59.9) | 0.028 |
| 3 | 59 989 (40.0) | 274 (27.0) | 0.277 | 852 (28.0) | 274 (27.0) | 0.022 |
| 4 | 2981 (2.0) | 8 (0.8) | 0.103 | 25 (0.8) | 8 (0.8) | 0.004 |
| 5 | 8 (0.0) | 1 (0.1) | 0.041 | 1 (0.0) | 1 (0.1) | 0.026 |
| Not assigned | 143 (0.1) | 1 (0.1) | 0.001 | 3 (0.1) | 1 (0.1) | 0.000 |
| Wound class 1 or 2, n (%) | 149 239 (99.5) | 1011 (99.7) | 0.033 | 3033 (99.7) | 1011 (99.7) | 0.000 |
| Mean operative time (SD) | 111.7 (71.4) | 79.9 (52.3) | 0.508 | 97.9 (60.7) | 79.9 (52.3) | 0.317 |
| Median operative time (range) | 93 (1–1165) | 64 (16–444) | N/A | 82 (9–654) | 66 (16–444) | N/A |
| Emergency, n (%) | 2662 (1.8) | 12 (1.2) | 0.049 | 30 (1.0) | 12 (1.2) | 0.019 |
*Boldface type indicates imbalance on demographics (SMD>0.1).
ASA, American Society of Anesthesiologists; SMD, standardized mean difference.