Finally, the last risk factor cited by experts was electrolyte imbalance. The electrolytes such as K+ (3·5–5 mEq/L), Ca2+ (4·5–5·5 mEq/L) and/or Mg2+ (1–2 mEq/L) contribute to the occurrence of changes in heart function. Increased or decreased plasma concentrations of these electrolytes compared to physiological parameters can lead to conduction or contraction disturbances, such as atrioventricular blockage, arrhythmia and cardiac arrest because of fibrillation or flaccid heart (Guyton and Hall, 2006; Smeltzer and Bare, 2008). Evidence of electrolyte imbalance and its effects on heart function is also provided by Polderman and Girbes (2004). On the basis of a prospective research with patients undergoing cardiac surgical interventions, they observed that those submitted to extracorporeal circulation were at high risk for elec-trolyte depletion, which may partly explain the high risk for tachyarrhythmia in those patients.