Zero-balance ultrafiltration (Z-BUF) is considered a significant method during cardiopulmonary bypass (CPB), and has always received support regarding its key role in monitoring electrolyte abnormalities including potassium and sodium derangements and managing them which occur commonly during CPB. With Z-BUF procedure's impact on controlling electrolyte abnormalities, we conducted a study in order to find out the most efficient solution regarding managing potassium and sodium levels to be selected as replacement fluid in Z-BUF out of the three commonly used normal saline, ringer's and ringer's lactate. a randomized clinical trial study was conducted and 90 patients were divided into three groups. Each group was given a certain solution out of the three normal saline (Z-BUF-NS), ringer's (Z-BUF-R), and ringer's lactate (Z-BUF-RL) with allocation concealment strategy then potassium and sodium levels were measured at 5 points of the whole procedure: prior to CPB and after anesthesia induction, cardioplegic solution's delivery, pre-Z-BUF, post-Z-BUFF, and at the end of CPB. Comparing pre-Z-BUF and post-CPB patients' serum potassium demonstrated a change from 4.7 0.9 mEq/L to 5.2 0.7 mEq/L in Z-BUF-RL, 4.4 0.6 mEq/L to 4.7 0.5mEq/L in Z-BUF-R, and 5.1 0.5 mEq/L to 5.1 0.5 mEq/L in Z-BUF-NS. No significant difference was observed between groups regarding managing K+ abnormalities. Changes in Na+ from pre-Z-BUF to post-CPB were as following: from 134 mEq/L to 133 mEq/L in Z-BUF-RL, 137 mEq/L to 137 mEq/L in Z-BUF-R, and 135.2 4 mEq/L to 136.5 4 mEq/L in Z-BUF-NS. Ringer's lactate managed sodium abnormalities more efficiently. Ringer's lactate is more efficient than Ringer's and normal saline regarding managing sodium and potassium abnormalities.