Table 2.
Demographic and clinical characteristics.
| Overall | Cohort 1 | Cohort 2 | P * | |
|---|---|---|---|---|
| (n = 1673) | (n = 902) | (n = 771) | ||
| Male, n (%) | 770 (46.0) | 436 (48.3) | 334 (43.3) | 0.04 |
| Age, yr | 49 (37–60) | 48 (36–60) | 49 (39–60) | 0.69 |
| Education, yr | 9 (6–9) | 9 (6–9) | 9 (9–14.5) | 0.31 |
| Smoking status, n (%) | 0.85 | |||
| Never smoker | 1397 (83.5) | 753 (83.5) | 644 (83.5) | |
| Former smoker | 222 (13.3) | 118 (13.1) | 104 (13.5) | |
| Current smoker | 54 (3.2) | 31 (3.4) | 23 (3.0) | |
| Drinker, n (%) | 0.47 | |||
| Never drinker | 1487 (88.9) | 804 (89.1) | 683 (88.6) | |
| Former drinker | 152 (9.1) | 83 (9.2) | 69 (8.9) | |
| Current drinker | 34 (2.0) | 15 (1.7) | 19 (2.5) | |
| Body mass index, kg/m2 | 22.3 (20.3–24.3) | 22.1 (20.3–24. 2) | 22.4 (20.3–24.3) | 0.85 |
| Preoperative SpO2, % | 98 (98-99) | 98 (98-99) | 98 (98-98) | 0.45 |
| Respiratory infection in the last month, n (%) | 28 (1.7) | 16 (1.8) | 12 (1.6) | 0.85 |
| ASA physical status, n (%) | 0.43 | |||
| 1 | 830 (49.6) | 464 (51.4) | 366 (47.5) | |
| 2 | 722 (43.2) | 380 (42.1) | 342 (44.4) | |
| 3 | 114 (6.8) | 54 (6.0) | 60 (7.8) | |
| 4 | 5 (0.3) | 3 (0.3) | 2 (0.3) | |
| 5 | 2 (0.1) | 1 (0.1) | 1 (0.1) | |
| Emergency surgery, n (%) | 102 (6.1) | 55 (6.1) | 47 (6.1) | 0.99 |
| Anesthesia, n (%) | 0.24 | |||
| General and combined# | 1251 (74.8) | 664 (73.6) | 587 (76.1) | |
| Neuraxial/regional | 422 (25.2) | 238 (26.4) | 184 (23.9) | |
| Surgical site, n (%) | <0.001 | |||
| Peripheral | 1015 (60.7) | 620 (68.7) | 395 (51.2) | |
| Abdominal | 600 (35.9) | 243 (26.9) | 357 (46.3) | |
| Intrathoracic | 58 (3.5) | 39 (4.3) | 19 (2.5) | |
| Duration of surgery, h | 0.63 | |||
| ≤2 h | 1238 (74.0) | 659 (73.1) | 579 (75.1) | |
| 2-3 h | 235 (14.0) | 132 (14.6) | 103 (13.4) | |
| >3 h | 200 (12.0) | 111 (12.3) | 89 (11.5) | |
| LOS, d | 8 (5–14) | 9 (6–14) | 8 (5–13) | 0.01 |
Data are median (quartile) unless otherwise specified.
SpO2: saturation of peripheral oxygen; ASA: American society of anesthesiologists; LOS: length of stay.
*Cohort 1 versus cohort 2; #this category included general anesthesia alone and general anesthesia combined with regional blockade.