Acute serum sodium concentration changes in pediatric patients undergoing cardiopulmonary bypass and the association with postoperative outcomes.

The objective of this study is to investigate the degree of serum sodium changes and its association with patient outcomes in pediatrics undergoing heart surgery with cardiopulmonary bypass (CPB). We reviewed the medical records of 275 pediatric patients who underwent heart surgery with CPB. Prior to CPB, hyponatremia (≤135 mmol/L) was observed in 21 of 275 patients. After initiation of CPB, serum sodium decreased significantly and severe hyponatermia (≤130 mmol/L) subsequently developed in 32 patients. At the end of CPB, however, hypernatremia (≥145 mmol/L) developed in 86 patients. The degree of acute serum sodium change during CPB was not associated with patient outcomes. However, the patients with preoperative hyponatremia and those with hypernatremia at the conclusion of CPB had longer hospital stays and higher postoperative complication rates. Lower serum sodium prior to CPB and higher serum sodium at the end of CPB, along with age and duration of the operation, were independently associated with worse in-hospital outcomes. Acute and transient hyponatremia occurred frequently after initiation of CPB, and then serum sodium immediately increased above preoperative levels at the end of CPB. Caution is required to avoid serum sodium overcorrection on the conclusion of CPB.