Association of hyponatraemia and renal function in type 1 cardiorenal syndrome

Abstract Background Hyponatraemia predicts type 1 cardiorenal syndrome in acute decompensated heart failure patients, which associates with poor outcome. Recovery from hyponatraemia has been found to associate with better outcome in acute decompensated heart failure patients, but its prognostic value regarding renal function remains unknown. Methods We performed a secondary analysis of CARRESS‐HF trial, and all patients included had worsening renal function (≥0.3 mg/dL increase in serum creatinine than the nadir). The serum sodium levels of patients were evaluated at baseline and day 4 and day 7 after randomization. Patients were grouped according to the status of hyponatraemia: recovery from hyponatraemia; no hyponatraemia; persistent hyponatraemia; and new‐onset hyponatraemia. Their associations with persistent worsening renal function (serum creatinine ≥ 0.3 mg/dL higher than the nadir at discharge) were explored. Results A total of 118 patients suffered from persistent worsening renal function. Baseline hyponatraemia was not associated with persistent worsening renal function (odds ratio = 0.495, P = .086). Patients in the recovery from hyponatraemia group had a lowest risk of persistent worsening renal function among the study population. Further, baseline serum sodium level was not associated with the risk of persistent worsening renal function (odds ratio = 1.055, P = .233), while the increases in serum sodium level at day 4 (odds ratio = 0.858, P = .003) and at day 7 (odds ratio = 0.821, P < .001) significantly predicted a lower risk of persistent worsening renal function. Conclusions Recovery from hyponatraemia associates with a lower risk of persistent worsening renal function, suggesting that hyponatraemia correction may improve renal outcomes in acute decompensated heart failure patients with type 1 cardiorenal syndrome.