Postoperative hyponatremia following calvarial vault remodeling in craniosynostosis

Background: The incidence, severity, and risk factors for the development of hyponatremia in patients undergoing craniosynostosis surgery are not well known. Objective: To determine the incidence and severity of hyponatremia as a complication in surgical correction of craniosynostosis and to identify risk factors for postoperative hyponatremia. Methods: A retrospective medical record review for 2003-2008 of the Cleft and Craniofacial Database was made. Specific data collected included sodium values, age, weight, type of surgery, duration of surgery, administration of DDAVP, composition and volume of pre-operative, intra-operative, postoperative parenteral fluids, volume of blood, colloid, and crystalloid transfused, estimated blood loss (EBL), medications, comorbidities, pre-operative signs of elevated intracranial pressure (ICP), syndromic vs nonsyndromic craniosynostosis, and the complications associated with hyponatremia. Results: A total of 72 records were reviewed. The incidence of postoperative hyponatremia was 30.6%. There was no intra-operative hyponatremia. While hospital stay was not prolonged, ICU stay was significantly longer (1.9 vs 2.9 days, P = 0.001). Elevated ICP was significantly associated with hyponatremia (P < 0.002). A greater volume of blood loss (EBL) was associated with postoperative hyponatremia (P = 0.019). Patients with normal pre-operative ICP were more likely to become hyponatremic if they were female (relative risk = 2.43; P < 0.05). The average decrease in sodium was greater in patients receiving hyponatremic (hypotonic) vs normonatremic (isotonic) postoperative IVF's (5.5 vs 3.2 mEq.l(-1), P = 0.039). There were no postoperative complications related to hyponatremia. Conclusions: The incidence of postoperative hyponatremia after calvarial vault remodeling was determined to be 30.6%. Hyponatremia was significantly associated with increased pre-operative ICP, blood loss, and female gender (normal pre-operative ICP). The average decrease in sodium was greater in patients receiving hyponatremic postoperative IVF's.