Tables 4 and 5 show the comparison between the survival group and the in-hospital mortality group, and the association of clinical factors, both modifiable and non-modifiable, with in-hospital mortality. The OR for mortality increased as the levels of the following modifiable factors increased: the serum K+ level and the difference between serum K+ levels at admission and at its highest point. Severe medical conditions, including infection, volume depletion, and bleeding, were significantly associated with a higher mortality rate. Furthermore, the development of AKI in patients with normal baseline renal function was a clear predictor of a higher mortality rate (OR 5.23, 95% CI 3.75 to 7.30; P < 0.001). In contrast, the mortality rate decreased in patients with AKI superimposed on CKD (OR 0.53, 95% CI 0.40 to 0.70; P < 0.001). These findings are demonstrated in Table 6, which evaluates the mortality rate in patients with AKI according to the presence or absence of underlying CKD. Patients with AKI superimposed on CKD had much lower mortality rates than those with AKI developing from normal baseline renal function (OR 0.42, 95% CI 0.23 to 0.74; P = 0.003) (Table 6). Patients who received CPR had much higher mortality rates than those who did not; in particular, CPR significantly increased the mortality rate when performed for causes other than those related to hyperkalemia. ICU treatment during hospitalization was also significantly associated with higher in-hospital mortality.