Intraoperative and postoperative hyponatremia with craniosynostosis surgery.

BACKGROUND:   An alarming incidence of significant intraoperative hyponatremia during major pediatric craniofacial surgery has recently been reported, the mechanism of which is unclear.

AIMS:   To establish the incidence and severity of hyponatremia occurring during and after major craniofacial surgery for craniosynostosis in our institution and identify any associated risk factors.

METHODS:   Retrospective review of case notes and blood test results for all cases of major craniofacial surgery for craniosynostosis in children under 10 years of age from January 2007 to May 2011. Hyponatremia was classified as: mild 131-134 mmol·l(-1) ; moderate 126-130 mmol·l(-1) ; and, severe ≤125 mmol·l(-1) . Analyses were performed to look for factors associated with hyponatremia including gender, weight, syndromic or not, duration of procedure, and volumes of crystalloid, colloid and blood administered.

RESULTS:   One hundred and two consecutive cases were identified. Mild intraoperative hyponatremia occurred in five (5%) of children. There were no cases of moderate or severe intraoperative hyponatremia. All five had normal sodium values within two hours of their single low readings of 134 mmol.l(-1) and none had any subsequent episodes of hyponatremia in the postoperative period. Intraoperative hyponatremia was associated with lower body weight (P = 0.002). Mild postoperative hyponatremia on the day of surgery (POD0) occurred in three other children (3%) with no identifiable associations. There were no cases of moderate or severe postoperative hyponatremia on POD0. Hyponatremia on the first postoperative day (POD1) was mild in 23 children (24%) and moderate in one child (1%). There were no cases of severe postoperative hyponatremia on POD1. Hyponatraemia on POD1 was associated with male gender (P = 0.042).

CONCLUSIONS:   Clinically significant intraoperative hyponatremia was not a feature of major craniofacial surgery in our institution. Mild postoperative hyponatremia was relatively common on POD1.