The Sodium Paradox: Dysnatremia and Mortality in Patients Implanted With Extracorporeal Mechanical Circulatory Support Devices

Abstract

Dysnatremia, abnormal serum sodium levels, has long been used as a marker for disease progression in heart failure patients. Classically, hyponatremia is associated with increased fluid volume in heart failure and is often a result of neuroendocrine dysfunction and poor cardiac output. Recent studies have noted that dysnatremia and hypernatremia are predictive of worsened outcomes in critical care and renal disease populations. We investigated the relationship between dysnatremia and postoperative outcomes in patients implanted with extracorporeal mechanical circulatory devices. A total of 97 patients who underwent implantation with the CentriMag mechanical circulatory assist system were included in this retrospective study. Patients were divided into 2 groups based on preoperative serum sodium level cutoff of 135 mEq/L. Outcomes and mortality were compared between groups. The mean age for the study population was 56.21 ± 15.13 years, and 57 patients (58.8%) were male. The mean time on CentriMag support was 22.7 days. Patients with serum sodium levels ≤135 mEq/L were noted to have significantly worsened indicators of preoperative cardiac function. However, patients with serum sodium levels >135 mEq/L had significantly shorter postoperative survival ( P = .006). When entered into a multivariate Cox proportional hazards model, sodium was an independent predictor for increased risk of mortality (hazard ratio: 1.224; 95% confidence interval: 1.009-1.485; P = .040). Our results indicate that elevated preoperative sodium in patients undergoing implantation of a temporary mechanical circulatory support system is predictive of worsened postoperative survival.