Abstract: Abstract Objective: To evaluate the effect of potassium magnesium aspartate applied in cardiovascular surgeries. Methods: 50 patients undergoing cardiovascular surgeries were randomly divided in to two groups with 25 cases each. During the CPB, Kcl was conventionally given in both groups. However, during the other processes of the surgeries, potassium magnesium aspartate (group A) or Kcl (group B) was given to the patients to supply potassium according to the analysis of blood gas. The amount of potassium ion was calculated after the surgeries, and the value of blood potassium, magnism, the incidence of arrhythmia are observed in different time points. Results: There is no statistical difference in the potassium supplement and the incidence of arrhythmia in both groups（P＞0.05). The effect of magnesium supplement in Group A is more obvious than Group B（P＜0.05）。

Key words: Potassium Magnesium Aspartate, Heart, Extracorporeal Circulation, Cardiac Surgical Procedures