Preoperative natremia and AKI after cardiac surgery: an international multicenter prospective cohort study

Whether preoperative natremia levels may play a role in the development of acute kidney injury (AKI) after cardiac surgery is uncertain. We conducted a cohort study to evaluate the influence of preoperative natremia on AKI in high-risk patients undergoing cardiac surgery. This multicenter prospective cohort study involved 14 British and Spanish hospitals, each under local ethics committee approval. The study population comprised all consecutive patients aged 18 years or older, with a Cleveland Clinic score ≥ 4, undergoing cardiac surgery from July to December 2017. The resultant 241 consecutive patients were classified according to tertiles of preoperative natremia levels (< 139, > 139–141, and > 141 mmol/L). The AKIN criteria were used to define AKI. Multivariable logistic regression was used to estimate the adjusted association between preoperative natremia and AKI. A potential link was observed between sodium levels ≤ 139 mmol/L and an increased risk of moderate-to-severe AKI relative to levels above 141 mmol/L (OR 2.01, 95% CI 1.02–3.95, p = 0.03), after multivariable adjustment for age and preoperative serum creatinine. No significant associations were observed between sodium levels and RRT or in-hospital mortality. Conclusions The results from this cohort of high-risk cardiac surgery patients lend tentative support to the hypothesis that preoperative natremia levels ≤ 139 mmol/L might be linked to a higher risk of moderate-to-severe AKI compared with levels above 141 mmol/L. These findings warrant further evaluation in a larger cohort.