Table 1.
Baseline characteristics of the study cohort stratified by time of ICU discharge
| Characteristics | Total | Nighttime discharges | Daytime discharges | P value |
|---|---|---|---|---|
| n: 19,622 | n = 3,505 (17.9 %) | n = 16,117 (82.1 %) | ||
| Male sex, n (%) | 11,357 (57.9) | 1,986 (56.7) | 9,371 (58.1) | 0.11 |
| Age (years) (mean [SD]) | 57.5 (18.0) | 57.2 (17.9) | 57.5 (18.0) | 0.30 |
| Apache II score (mean [SD]) | 19.4 (7.5) | 20.1 (7.6) | 19.3 (7.4) | <0.001 |
| Medical admission, n (%) | 13,018 (66.3) | 2,596 (74.1) | 10,422 (64.7) | <0.001 |
| Post-operative, n (%) | 6,604 (33.7) | 909 (25.9) | 5,695 (35.3) | <0.001 |
| Comorbid illness, n (%) | ||||
| None | 15,180 (77.4) | 2,662 (76.0) | 12,518 (77.7) | 0.027 |
| One | 3,927 (20.0) | 730 (20.8) | 3,197 (19.8) | 0.19 |
| Two or more | 515 (2.6) | 113 (3.2) | 402 (2.5) | 0.014 |
| Comorbid condition, n (%) | ||||
| Hepatic failure | 873 (4.5) | 150 (4.3) | 723 (4.5) | 0.59 |
| Immunosuppression | 981 (5.0) | 207 (5.9) | 774 (4.8) | 0.007 |
| Chronic lung disease | 1,355 (6.9) | 228 (6.5) | 1,127 (7.0) | 0.30 |
| Chronic renal failure | 613 (3.1) | 159 (4.5) | 454 (2.8) | <0.001 |
| Hematologic cancer | 314 (1.6) | 63 (1.8) | 251 (1.6) | 0.31 |
| Metastatic cancer | 465 (2.4) | 83 (2.4) | 382 (2.4) | 0.99 |
| Congestive heart failure | 293 (1.5) | 53 (1.5) | 240 (1.5) | 0.92 |
| AIDS | 82 (0.4) | 16 (0.5) | 66 (0.4) | 0.69 |
| Primary diagnosis, n (%) | ||||
| Respiratory | 5,940 (30.3) | 1,099 (31.4) | 4,841 (30.0) | 0.12 |
| Gastrointestinal | 3,342 (17.0) | 520 (14.8) | 2,822 (17.5) | <0.001 |
| Cardiovascular | 2,822 (14.4) | 448 (12.8) | 2,374 (14.7) | 0.003 |
| Sepsis | 1,548 (7.9) | 295 (8.4) | 1,253 (7.8) | 0.20 |
| Trauma | 1,699 (8.7) | 312 (8.9) | 1,387 (8.6) | 0.57 |
| Metabolic | 1,640 (8.4) | 315 (9.0) | 1,325 (8.2) | 0.14 |
| Neurologic | 1,385 (7.1) | 293 (8.4) | 1,092 (6.8) | 0.001 |
| Renal | 626 (3.2) | 121 (3.5) | 505 (3.1) | 0.33 |
| Other | 620 (3.2) | 102 (2.9) | 518 (3.2) | 0.35 |
| Mechanical ventilation, n (%) | 14,349 (73.1) | 2,641 (75.3) | 11,708 (72.6) | 0.001 |
| Source of admission, n (%) | ||||
| Emergency department | 6,370 (32.5) | 1,275 (36.4) | 5,095 (31.6) | <0.001 |
| Operating room - Elective | 3,165 (16.1) | 401 (11.4) | 2,764 (17.1) | <0.001 |
| Operating room – Emergency | 3,438 (17.5) | 508 (14.5) | 2,930 (18.2) | <0.001 |
| Other hospital | 3,140 (16.0) | 603 (17.2) | 2,537 (15.7) | 0.032 |
| Ward | 3,509 (17.9) | 718 (20.5) | 2,791 (17.3) | <0.001 |
| Year of admission, n (%) | ||||
| 2002/2003 | 3852 (19.6) | 577 (14.9) | 3275 (75.1) | <0.01* |
| 2004/2005 | 4929 (25.1) | 801 (16.2) | 4128 (83.8) | |
| 2006/2007 | 5400 (27.5) | 1007 (18.6) | 4393 (81.4) | |
| 2008/2009 | 5441 (27.7) | 1120 (20.6) | 4321 (79.4) | |
| ICU LOS, (d) (med [IQR]) | 3 (1–7) | 3 (1–7) | 3 (2–7) | 0.09 |
| Source of discharge, n (%) | ||||
| Ward | 17,935 (91.4) | 3,199 (91.3) | 14,736 (91.4) | 0.75 |
| Acute care | 979 (5.0) | 260 (7.4) | 719 (4.5) | <0.001 |
| Home | 585 (3.0) | 31 (0.9) | 554 (3.4) | <0.001 |
| Left without authorization | 75 (0.4) | 11 (0.3) | 64 (0.4) | 0.46 |
| Chronic care | 48 (0.2) | 4 (0.1) | 44 (0.3) | 0.08 |
| Weekend discharges | 4,676 (23.8) | 779 (16.7) | 3,897 (83.3) | 0.014 |
| Weekday discharges | 14,946 (76.2) | 2,726 (18.2) | 12,220 (81.8) | 0.014 |
Legend: AIDS: Acquired Immune Deficiency Syndrome; ICU: Intensive Care Unit; LOS: Length of stay
*Linear regression