After coronary artery bypass grafting (CABG), maintaining serum potassium at the upper normal limit lacks clear evidence for its impact on clinical outcomes. Also, potassium variability might signal poor prognosis. This retrospective study aimed to assess how postoperative serum potassium levels and variability affect 1-year mortality rate in CABG patients. This retrospective study was based on data from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. We analyzed the relationships between the average value, coefficient of variation (CV), and change trajectory of postoperative serum potassium levels and 1-year mortality rate, using logistic regression as the primary analytical method. A total of 50,903 potassium measurements, all collected during the postoperative ICU stay, from 4,606 patients were analyzed in this study. The patients whose average serum potassium level was maintained at 3.5-4 mmol/L had the lowest mortality rate of 1.33% (p = 0.004) and pointed a significant inflection point at 3.85mmo/L. The CV in deceased patients was greater than that in surviving patients (p 20% had significantly higher mortality (11.63%; adjusted OR = 4.72, 95% CI: 1.32–15.17, p = 0.011). In addition, the patients with highly fluctuating potassium change trajectories had the highest 1-year mortality rate of 19.72%. Moreover, the shorter the time to the stability of the serum potassium level, the lower the mortality rate. In this retrospective cohort of patients who underwent CABG, those with a mean potassium level between 3.5 and 4.0 mmol/l or minimal potassium variability correlated with the lowest observed 1-year mortality risk. Higher levels above 3.85 mmol/L correlated with increased mortality; mild hypokalemia risk remained inconclusive.
Zhang et al. (Thu,) studied this question.