Table 5.
Baseline Characteristics by Facility Volume
| Variable | No. | Overall (n = 1,069) |
Volume per Year < 4 (n = 529) |
Volume per Year ≥4 (n = 540) |
p Value |
|---|---|---|---|---|---|
| Age at time of operation, years | 1,069 | 50.2 ± 15.5 | 51.1 ± 15.8 | 49.3 ± 15.1 | 0.06 |
| Male | 1,068 | 456 (43) | 256 (48) | 200 (37) | <0.001 |
| Race | 1,040 | 0.011 | |||
| Asian | 24 (2) | 15 (3) | 9(2) | ||
| Black | 107 (10) | 68 (13) | 39 (7) | ||
| White | 866 (83) | 406 (79) | 460 (87) | ||
| Hispanic | 1(0) | 1(0) | 0 (0) | ||
| Native American | 7 (1) | 5 (1) | 2 (0) | ||
| Other | 35 (3) | 17 (3) | 18 (3) | ||
| Height, cm | 1,024 | 167.8 ± 13.3 | 168.5 ± 11.8 | 167.1 ± 14.6 | 0.09 |
| Weight, kg | 1,034 | 84.6 ± 23.9 | 87.1 ± 25.6 | 82.1 ± 21.7 | <0.001 |
| Benign indication | 1,069 | 807 (75) | 383 (72) | 424 (79) | 0.020 |
| Cervical approach | 1,069 | 820 (77) | 364 (69) | 456 (84) | <0.001 |
| BMI (obesity: BMI > 30.0) | 1,023 | 0.07 | |||
| ≤18.5 | 28 (3) | 13 (3) | 15 (3) | ||
| >18.5 and ≤25.0 | 271 (26) | 125 (24) | 146 (29) | ||
| >25.0 and ≤30.0 | 294 (29) | 144 (28) | 150 (30) | ||
| >30.0 and ≤35.0 | 207 (20) | 106 (20) | 101 (20) | ||
| >35.0 | 223 (22) | 131 (25) | 92 (18) | ||
| Smoking history | 1,067 | 465 (44) | 257 (49) | 208 (39) | <0.001 |
| ASA class | 1,069 | <0.001 | |||
| 1 | 8(1) | 3(1) | 5(1) | ||
| 2 | 256 (24) | 64 (12) | 192 (36) | ||
| 3 | 622 (58) | 338 (64) | 284 (53) | ||
| 4 | 181 (17) | 123 (23) | 58 (11) | ||
| 5 | 2(0) | 1 (0) | 1 (0) | ||
| Zubrod score | 1,069 | <0.001 | |||
| 0 | 93 (9) | 57 (11) | 36 (7) | ||
| 1 | 803 (75) | 359 (68) | 444 (82) | ||
| 2 | 99 (9) | 67 (13) | 32 (6) | ||
| 3 | 50 (5) | 29 (5) | 21 (4) | ||
| 4 | 23 (2) | 16 (3) | 7(1) | ||
| 5 | 1 (0) | 1(0) | 0 (0) | ||
| Hypertension | 1,044 | 457 (44) | 266 (51) | 191 (36) | <0.001 |
| Diabetes | 1,044 | 251 (24) | 138 (27) | 113 (22) | 0.06 |
| Congestive heart failure | 1,041 | 44 (4) | 32 (6) | 12 (2) | 0.002 |
| Coronary artery disease | 1,041 | 127 (12) | 71 (14) | 56 (11) | 0.13 |
| Peripheral vascular disease | 1,042 | 37 (4) | 27 (5) | 10 (2) | 0.004 |
| Renal dysfunction | 1,037 | 17 (2) | 9 (2) | 8 (2) | 0.78 |
| Last creatinine (mg/dL) level | 997 | 1.0 ± 0.9 | 1.0 ± 1.0 | 0.9 ± 0.7 | 0.21 |
| Steroids | 1,040 | 52 (5) | 36 (7) | 16 (3) | 0.004 |
| Prior cardiothoracic operation | 1,040 | 190 (18) | 127 (25) | 63 (12) | <0.001 |
| Weight loss (kg) in past 3 months | 897 | 0.3 ± 1.7 | 0.3 ± 1.5 | 0.3 ± 1.8 | 0.76 |
| Last hemoglobin (g/dL) level | 1,007 | 12.9 ± 1.8 | 12.8 ± 1.9 | 13.1 ± 1.7 | 0.008 |
| COPD | 1,040 | 160 (15) | 107 (21) | 53 (10) | <0.001 |
| Interstitial lung disease | 1,039 | 4 (0) | 3 (1) | 1 (0) | 0.31 |
| Pulmonary hypertension | 1,025 | 0.24 | |||
| Yes | 11 (1) | 8 (2) | 3 (1) | ||
| No | 768 (75) | 370 (74) | 398 (76) | ||
| Not applicable | 246 (24) | 124 (25) | 122 (23) | ||
| Cerebrovascular history | 1,035 | 0.16 | |||
| No CVD history | 962 (93) | 468 (91) | 494 (94) | ||
| Transient ischemic attack | 23 (2) | 14 (3) | 9 (2) | ||
| Cerebrovascular accident | 50 (5) | 30 (6) | 20 (4) | ||
| OR time, minutesa | 1,069 | 320.6 ± 132.8 | 300.4 ± 128.2 | 340.4 ± 134.4 | <0.001 |
| Intraoperative transfusion | 1,044 | 19 (2) | 12 (2) | 7 (1) | 0.24 |
a
Calculated as OR exit - OR entry.
Values are expressed as mean ± SD or n (%).
ASA = American Society of Anesthesiologists; BMI = body mass index; COPD = chronic obstructive pulmonary disease; CVD = cerebrovascular disease; No. = number; OR = operating room.