Table 1 Baseline patient characteristics across three categories of blood sodium levels
| Â | Sodium (mEq/L) | Â | ||
|---|---|---|---|---|
|  | < 135 | 135–145 | > 145 | p-value |
|  | (n = 87,476) | (n = 1,010,167) | (n = 11,061) |  |
Age | 61.82 ± 16.52 | 57.29 ± 16.65 | 63.38 ± 15.89 | < 0.0001 |
  < 50 | 19,723 (22.6) | 316,094 (31.3) | 2015 (18.2) | < 0.0001 |
 50–64 | 26,535 (30.3) | 330,181 (32.7) | 3500 (31.6) | |
 65–79 | 27,788 (31.8) | 271,429 (26.9) | 3653 (33.0) | |
  ≥ 80 | 13,430 (15.4) | 92,463 (9.2) | 1893 (17.1) | |
Sex, female | 44,389 (50.9) | 570,528 (56.6) | 6142 (55.6) | < 0.0001 |
Race, White | 66,224 (84.8) | 759,216 (84.6) | 7777 (78.0) | < 0.0001 |
Surgery type | ||||
 General surgery | 54,423 (62.2) | 656,018 (64.9) | 7529 (68.1) | < 0.0001 |
 Gynecology | 1503 (1.7) | 35,143 (3.5) | 242 (2.2) | |
 Neurosurgery | 2234 (2.6) | 26,292 (2.6) | 262 (2.4) | |
 Orthopedics | 6831 (7.8) | 87,304 (8.6) | 782 (7.1) | |
 Otolaryngology (ENT) | 922 (1.1) | 15,953 (1.6) | 206 (1.9) | |
 Plastics | 615 (0.7) | 12,522 (1.2) | 150 (1.4) | |
 Thoracic | 1289 (1.5) | 10,221 (1.0) | 128 (1.2) | |
 Urology | 2400 (2.7) | 39,573 (3.9) | 361 (3.3) | |
 Vascular | 15,853 (18.1) | 116,611 (11.5) | 1317 (11.9) | |
 Cardiac surgery | 1404 (1.6) | 10,524 (1.0) | 83 (0.8) | |
Principal anesthesia technique, general | 80,842 (92.4) | 929,863 (92.1) | 10,238 (92.6) | < 0.0001 |
ASA classification | ||||
 I-II | 25,653 (29.4) | 512,018 (50.8) | 3642 (33.0) | < 0.0001 |
 III | 45,074 (51.7) | 422,264 (41.9) | 4666 (42.3) | |
 IV-V | 16,531 (18.9) | 73,419 (7.3) | 2721 (24.7) | |
Wound classification, dirty/infected | 17,210 (19.7) | 59,804 (5.9) | 1163 (10.5) | < 0.0001 |
Inpatient status | 74,600 (85.3) | 704,245 (69.7) | 8451 (76.4) | < 0.0001 |
Emergency case | 25,053 (28.6) | 123,927 (12.3) | 2396 (21.7) | < 0.0001 |
Transfusion in 72 h before surgery | 1992 (2.3) | 8644 (0.9) | 643 (5.8) | < 0.0001 |
Do not resuscitate (DNR) status | 1601 (1.8) | 6425 (0.6) | 306 (2.8) | < 0.0001 |
Functional health status before surgery | ||||
 Independent | 73,530 (84.2) | 952,051 (94.4) | 8620 (78.1) | < 0.0001 |
 Partially dependent | 10,052 (11.5) | 42,984 (4.3) | 978 (8.9) | |
 Totally dependent | 3708 (4.3) | 14,080 (1.4) | 1439 (13.0) | |
Dyspnea | 13,284 (15.2) | 106,592 (10.6) | 1755 (15.9) | < 0.0001 |
CHF 30 days before surgery | 2530 (2.9) | 9234 (0.9) | 443 (4.0) | < 0.0001 |
History of angina 1 month before surgery | 1579 (1.8) | 10,498 (1.0) | 163 (1.5) | < 0.0001 |
History of MI 6 months before surgery | 1650 (1.9) | 7518 (0.7) | 267 (2.4) | < 0.0001 |
Previous PCI | 7353 (8.4) | 61,587 (6.1) | 881 (8.0) | < 0.0001 |
Previous cardiac surgery | 8133 (9.3) | 59,855 (5.9) | 948 (8.6) | < 0.0001 |
Hypertension requiring medication | 55,678 (63.7) | 510,100 (50.5) | 6682 (60.4) | < 0.0001 |
History of revascularization/amputation for peripheral vascular disease | 8298 (9.5) | 40,414 (4.0) | 580 (5.2) | < 0.0001 |
Smoking within 1 year | 22,555 (25.8) | 197,346 (19.5) | 2045 (18.5) | < 0.0001 |
Current pneumonia | 1537 (1.8) | 4815 (0.5) | 514 (4.7) | < 0.0001 |
History of severe COPD | 8372 (9.6) | 52,570 (5.2) | 967 (8.7) | < 0.0001 |
Ventilator dependent | 1926 (2.2) | 7756 (0.8) | 1193 (10.8) | < 0.0001 |
Ascites | 2427 (2.8) | 6325 (0.6) | 286 (2.6) | < 0.0001 |
Esophageal varices | 302 (0.4) | 1017 (0.1) | 27 (0.2) | < 0.0001 |
Acute renal failure | 1800 (2.1) | 5066 (0.5) | 336 (3.0) | < 0.0001 |
Currently on dialysis | 4758 (5.4) | 18,196 (1.8) | 353 (3.2) | < 0.0001 |
Impaired sensorium | 2018 (2.3) | 6524 (0.7) | 660 (6.0) | < 0.0001 |
Coma > 24 h | 136 (0.2) | 596 (0.1) | 99 (0.9) | < 0.0001 |
History of transient ischemic attacks (TIA) | 3662 (4.2) | 31,358 (3.1) | 421 (3.8) | < 0.0001 |
CVA/stroke with neurological deficit | 3432 (3.9) | 24,497 (2.4) | 630 (5.7) | < 0.0001 |
CVA/stroke with no neurological deficit | 2941 (3.4) | 21,936 (2.2) | 345 (3.1) | < 0.0001 |
Tumor involving CNS | 498 (0.6) | 3703 (0.4) | 62 (0.6) | < 0.0001 |
Bleeding disorders | 9989 (11.4) | 57,672 (5.7) | 1195 (10.8) | < 0.0001 |
> 10% loss body weight in previous 6 months | 4158 (4.8) | 19,804 (2.0) | 376 (3.4) | < 0.0001 |
Disseminated cancer | 3694 (4.2) | 21,246 (2.1) | 329 (3.0) | < 0.0001 |
Chemotherapy ≤30 days pre-operative | 2051 (2.3) | 14,897 (1.5) | 239 (2.2) | < 0.0001 |
Radiotherapy in last 90 days | 1011 (1.2) | 7705 (0.8) | 100 (0.9) | < 0.0001 |
BMI | 28.40 ± 8.15 | 30.31 ± 8.42 | 29.57 ± 8.30 | < 0.0001 |
  < 18.5 | 4085 (4.9) | 20,342 (2.1) | 343 (3.2) | < 0.0001 |
 18.5–24.9 | 27,699 (33.1) | 249,205 (25.3) | 2895 (27.3) | |
 25.0–29.9 | 24,643 (29.4) | 300,443 (30.5) | 3209 (30.3) | |
 30.0–34.9 | 13,555 (16.2) | 192,841 (19.6) | 2068 (19.5) | |
  ≥ 35.0 | 13,716 (16.4) | 221,151 (22.5) | 2083 (19.7) | |
Diabetes mellitus with oral agents or insulin | 23,275 (26.6) | 167,543 (16.6) | 2174 (19.7) | < 0.0001 |
Alcohol > 2 drinks/day 2 wks before admission | 4925 (5.6) | 25,735 (2.6) | 323 (2.9) | < 0.0001 |
Open wound/wound infection | 11,046 (12.6) | 43,031 (4.3) | 1120 (10.1) | < 0.0001 |
Steroid use for chronic condition | 4717 (5.4) | 32,860 (3.3) | 591 (5.3) | < 0.0001 |
Systemic sepsis | 21,684 (25.0) | 72,666 (7.3) | 2411 (21.9) | < 0.0001 |
Prior operation within 30 days | 6239 (7.1) | 25,921 (2.6) | 960 (8.7) | < 0.0001 |