| Variables | Pre-op N = 305(%) | 4 weeks N = 305 (%) | X2 | P-value |
| Sodium, mmol/l | ||||
| ≤125 | 7 (2.3) | 19 (6.2) | 5.3 | 0.001 |
| 125 - 134.9 | 87 (28.5) | 163 (53.5) |
| |
| 135 - 145 | 211 (69.2) | 123 (40.3) |
|