Table 1. Preoperative clinical characteristics and outcomes of the cohort stratified by the occurrence of acute kidney injury within seven days after surgery.
| Acute Kidney Injury onset within seven days after surgery | |||
|---|---|---|---|
| No | Yes | ||
| Overall cohort (N = 2,911) | (N = 1,748, 60%) | (N = 1,163, 40%) | |
| Demographic features | |||
| Age, median (25th-75th) | 60 (49, 69) | 58 (47, 67) | 63 (52, 72)a |
| Male gender, n (%) | 1760 (60) | 1007 (58) | 753 (65) a |
| Race, n (%) | |||
| White | 2374 (82) | 1440 (82) | 934 (80) |
| African American | 265 (9) | 150 (9) | 115 (10) |
| Hispanic | 117 (4) | 64 (4) | 53 (5) |
| Missing | 87 (3) | 50 (3) | 37 (3) |
| Other | 68 (2) | 44 (3) | 24 (2) |
| Primary insurance, n (%)a | |||
| Private | 1208 (42) | 797 (46) | 411 (35) |
| Medicare | 1204 (41) | 635 (36) | 569 (49) |
| Medicaid | 340 (12) | 198 (11) | 142 (12) |
| Uninsured | 159 (5) | 118 (7) | 41 (4) |
| Socio-economic features | |||
| Neighborhood characteristics | |||
| Rural area, n (%) | 767 (27) | 467 (27) | 300 (26) |
| Total population, median (25th-75th) | 19162 (10639, 30611) | 18931 (10510, 30611) | 19287 (11056, 30533) |
| Median income, median (25th-75th) | 34372 (29980, 41410) | 34328 (29854, 41410) | 34459 (30084, 41410) |
| Total proportion of African-Americans (%), median (25th-75th) | 9.6 (3.9, 17.6) | 9.5 (3.9, 16.5) | 9.6 (3.7, 19.5) |
| Total proportion of Hispanic (%), median (25th-75th) | 4.3 (2.5, 6.8) | 4.3 (2.6, 6.7) | 4.1 (2.5, 7.1) |
| Distance from residency to hospital (km), median (25th-75th) | 68 (29, 143) | 61 (28, 132) | 73 (31, 153)a |
| Population proportion below poverty (%), median (25th-75th) | 12.0 (8.2, 17.4) | 12.1 (8.3, 17.2) | 11.8 (8.0, 17.4) |
| Comorbidity features | |||
| Charlson's comorbidity index (CCI), median (25th-75th) | 2 (1, 3) | 1 (0, 3) | 2 (1, 3)a |
| Chronic kidney disease, n (%) | 346 (12) | 73 (4) | 273 (23)a |
| Cancer, n (%) | 418 (15) | 303 (17) | 115 (10)a |
| Diabetes, n (%) | 539 (19) | 297 (17) | 242 (21)a |
| Chronic pulmonary disease, n (%) | 656 (23) | 331 (19) | 325 (28)a |
| Peripheral vascular disease, n (%) | 692 (24) | 334 (20) | 358 (31)a |
| Cerebrovascular disease, n (%) | 248 (9) | 154 (9) | 94 (8) |
| Congestive heart failure, n (%) | 510 (18) | 180 (10) | 330 (28)a |
| Myocardial infarction, n (%) | 308 (11) | 140 (8) | 168 (15)a |
| Liver disease, n (%) | 393 (14) | 170 (10) | 223 (20)a |
| Operative features | |||
| Admission | |||
| Weekend admission, n (%) | 472 (16) | 255 (15) | 217 (19)a |
| Admission source, n (%)a | |||
| Outpatient setting | 1753 (61) | 1105 (64) | 648 (56) |
| Emergency room | 583 (20) | 362 (21) | 221 (19) |
| Transfer | 560 (19) | 268 (15) | 292 (25) |
| Admission month (top 3 categories), n (%) | |||
| September | 279 (10) | 168 (10) | 111 (10) |
| October | 273 (9) | 174 (10) | 99 (9) |
| June | 254 (9) | 162 (9) | 92 (8) |
| Number of operating surgeons, n | 129 | 112 | 82 |
| Number of procedures per operating Surgeon, n (%)a | |||
| First rank | 422 (15) | 181 (10) | 241 (21) |
| Second rank | 267 (9) | 197 (11) | 70 (6) |
| Third rank | 258 (9) | 129 (7) | 129 (11) |
| Admitting service, n (%)a | |||
| Surgery | 2545 (87) | 1588 (91) | 957 (82) |
| Medicine | 366 (13) | 160 (9) | 206 (18) |
| Emergent surgery, n (%) | 1352 (46) | 748 (43) | 604 (52)a |
| Time between admission and operation (days) | 0 (0, 2) | 0 (0, 1) | 1 (0, 4)a |
| Surgery type, n (%)a | |||
| Cardiothoracic Surgery | 1415 (49) | 676 (39) | 739 (64) |
| Non-Cardiac General Surgery | 952 (33) | 614 (35) | 338 (29) |
| Neurologic Surgery | 301 (10) | 271 (16) | 30 (3) |
| Specialty Surgeriesb | 243 (8) | 187 (11) | 56 (5) |
| Admission day medications | |||
| Diuretics | 600 (21) | 285 (16) | 315 (27)a |
| Bicarbonate | 295 (10) | 144 (8) | 151 (13)a |
| Angiotensin-Converting-Enzyme Inhibitors | 351 (12) | 182 (10) | 169 (15)a |
| Antiemetic | 1413 (49) | 946 (54) | 467 (40)a |
| Betablockers | 872 (30) | 513 (29) | 359 (31) |
| Statin | 502 (17) | 272 (16) | 230 (20)a |
| Vasopressors or inotropes | 424 (15) | 201 (12) | 223 (20)a |
| Outcomes, n (%) | |||
| Acute kidney injury | |||
| Onset within 3 days of surgery | 998 (34) | 998 (86) | |
| Onset within 7 days of surgery | 1163 (40) | 1163 (100) | |
| At any time after surgery | 1339 (46) | 176 (10) | 1163 (100) |
| Worst stage of acute kidney injuryc | |||
| Stage 1 | 695 (52) | 685 (59) | |
| Stage 2 | 303 (23) | 237 (20) | |
| Stage 3 | 338 (25) | 238 (20) | |
| Renal replacement therapy | 154 (12) | 142 (12) | |
| Intensive care unit admission > 48 hours | 1800 (62) | 894 (51) | 906 (78)a |
| Mechanical ventilation > 48 hours | 833 (29) | 322 (18) | 511 (44)a |
| Sepsis | 266 (9) | 99 (6) | 167 (14)a |
| Wound complications | 73 (3) | 29 (2) | 44 (4)a |
| Cardiovascular complications | 425 (15) | 168 (10) | 257 (22) |
| Venous thromboembolism | 133 (5) | 61 (4) | 72 (6)a |
a p-value < 0.05 when comparing patients with and without acute kidney injury.
b Specialty surgery includes urological, orthopedics, gynecological, ear nose throat surgeries, ophthalmology and plastic surgery.
c Percentages are among patients with acute kidney injury. For overall cohort, numbers for acute kidney injury at any time during hospitalization are reported. Stage 3 includes cases with and without dialysis.