Table 1.
Baseline clinical characteristics
| Variables | All | Change in serum [Na+] during hospitalization (mEq/L) |
||||||
|---|---|---|---|---|---|---|---|---|
| 0–1 | 2–3 | 4–5 | 6–7 | 8–9 | 10–11 | ≥12 | ||
| N | 60 944 | 7867 | 14 626 | 13 711 | 9362 | 6172 | 3757 | 5449 |
| Age (year), mean ± SD | 63 ± 17 | 61 ± 17 | 62 ± 17 | 63 ± 17 | 64 ± 17 | 64 ± 17 | 64 ± 16 | 63 ± 16 |
| Male, n (%) | 32 685 (54) | 4123 (52) | 7743 (53) | 7266 (53) | 5031 (54) | 3336 (54) | 2118 (56) | 3068 (56) |
| Caucasian, n (%) | 56 706 (54) | 7342 (93) | 13 724 (94) | 12 802 (93) | 8681 (93) | 5689 (92) | 3478 (93) | 4990 (92) |
| Principal diagnosis, n (%) | ||||||||
| Cardiovascular | 15 141 (25) | 1409 (18) | 3015 (21) | 2937 (21) | 2251 (24) | 1926 (31) | 1484 (40) | 2119 (39) |
| Endocrine/metabolic | 1748 (3) | 169 (2) | 326 (2) | 412 (3) | 287 (3) | 197 (3) | 115 (3) | 242 (4) |
| Gastrointestinal | 6042 (10) | 658 (8) | 1398 (10) | 1516 (11) | 1026 (11) | 620 (10) | 337 (9) | 487 (9) |
| Hematology/oncology | 8830 (14) | 1111 (14) | 2103 (14) | 2140 (16) | 1506 (16) | 930 (15) | 434 (12) | 606 (11) |
| Infectious disease | 2276 (4) | 116 (1) | 317 (2) | 425 (3) | 451 (5) | 331 (5) | 227 (6) | 409 (8) |
| Respiratory | 2801 (4) | 276 (4) | 622 (4) | 655 (5) | 523 (6) | 301 (5) | 170 (5) | 254 (5) |
| Injury/poisoning | 9511 (16) | 1260 (16) | 2478 (17) | 2313 (17) | 1434 (15) | 857 (14) | 453 (12) | 716 (13) |
| Genitourinary | 1967 (3) | 193 (2) | 432 (3) | 475 (3) | 383 (4) | 230 (4) | 102 (3) | 152 (3) |
| Other | 12 628 (21) | 2675 (34) | 3935 (27) | 2838 (21) | 1501 (16) | 780 (13) | 435 (12) | 464 (9) |
| CCI score, mean ± SD | 1.9 ± 2.4 | 1.6 ± 2.2 | 1.8 ± 2.4 | 2.0 ± 2.5 | 2.2 ± 2.6 | 2.1 ± 2.5 | 2.0 ± 2.4 | 2.0 ± 2.3 |
| Comorbidity, n (%) | ||||||||
| CAD | 5042 (8) | 516 (7) | 1165 (8) | 1199 (9) | 820 (9) | 562 (9) | 298 (8) | 482 (9) |
| CHF | 4870 (8) | 339 (4) | 926 (6) | 1084 (8) | 915 (10) | 621 (10) | 364 (10) | 621 (11) |
| PAD | 2144 (4) | 159 (2) | 463 (3) | 473 (3) | 377 (4) | 262 (4) | 147 (4) | 263 (5) |
| Stroke | 4916 (8) | 529 (7) | 1078 (7) | 1177 (9) | 792 (8) | 564 (9) | 302 (8) | 474 (9) |
| DM | 13 094 (21) | 1339 (17) | 2842 (19) | 2942 (21) | 2206 (24) | 1519 (25) | 881 (23) | 1365 (25) |
| COPD | 5790 (10) | 536 (7) | 1240 (8) | 1282 (9) | 1004 (11) | 678 (11) | 413 (11) | 637 (12) |
| Cirrhosis | 1738 (3) | 165 (2) | 353 (2) | 373 (3) | 299 (3) | 200 (3) | 137 (4) | 211 (4) |
| eGFR (mL/min/1.73 m2), mean ± SD | 75 ± 29 | 82 ± 24 | 79 ± 27 | 75 ± 29 | 73 ± 31 | 71 ± 31 | 72 ± 30 | 69 ± 31 |
| Admission [Na+], mean ± SD | 138 ± 4 | 139 ± 3 | 138 ± 3 | 138 ± 3 | 137 ± 4 | 137 ± 5 | 137 ± 5 | 137 ± 7 |
| <135, n (%) | 10 066 (17) | 488 (6) | 1216 (8) | 2004 (15) | 2023 (22) | 1624 (26) | 1025 (27) | 1686 (31) |
| 135–145, n (%) | 50 026 (82) | 7360 (94) | 13 350 (91) | 11 606 (85) | 7214 (77) | 4429 (72) | 2634 (70) | 3433 (63) |
| 145, n (%) | 852 (1.4) | 19 (0.2) | 60 (0.4) | 101 (0.7) | 125 (1) | 119 (2) | 98 (3) | 330 (6) |
| Admission [Na+], n (%) | ||||||||
| <138 | 25 013 (41) | 2183 (28) | 4944 (34) | 5986 (44) | 4637 (50) | 3004 (49) | 1701 (45) | 2558 (47) |
| 138–142> | 30 702 (50) | 5286 (67) | 8762 (60) | 6671 (49) | 3916 (42) | 2506 (41) | 1592 (42) | 1969 (36) |
| 142 | 5229 (9) | 398 (5) | 920 (6) | 1054 (8) | 809 (9) | 662 (11) | 464 (12) | 922 (17) |
| Hospital-acquired hyponatremia (<135 mEq/L), n (%) | 11 044 (18) | 77 (1) | 521 (4) | 1273 (9) | 2019 (22) | 2321 (38) | 1836 (50) | 2937 (54) |
| Hospital-acquired hypernatremia (>145 mEq/L), n (%) | 4128 (7) | 6 (0.1) | 76 (0.5) | 271 (2) | 451 (5) | 514 (8) | 560 (15) | 2250 (41) |
| Number of serum [Na+] measurements, median (IQR) | 4 (3–8) | 2 (2–3) | 3 (2–4) | 4 (3–6) | 6 (4–9) | 9 (5–12) | 10 (8–15) | 16 (10–27) |
| Length of hospital stay, median (IQR) | 5 (3–8) | 3 (3–4) | 4 (3–5) | 5 (3–7) | 6 (4–8) | 7 (5–10) | 8 (5–12) | 11 (7–21) |
CAD, coronary artery disease; CHF, congestive heart failure; PAD, peripheral artery disease; DM, diabetes mellitus; COPD, chronic obstructive pulmonary disease.