Hypernatriuria

Abstract: Objective To analyze the clinical value of 24–hour urinary sodium determination in children with postural tachycardia syndrome (POTS). Method Fifty–eight POTS children and 10 healthy children (control group) from Peking University First Hospital during June 2012 to May 2014 were enrolled. Their 24–hour urinary sodium and plasma sodium levels were compared. Correlation analysis was done between 24–hour urinary sodium and symptom scores in children with POTS. All patients were treated with oral rehydration salts. The POTS patients were divided into hyponatriuria group (urinary sodium < 124 mmol/24 h) and hypernatriuria group (urinary sodium ≥ 124 mmol/24 h). Kaplan–Meier curve was used to analyze the effects of different 24–hour urinary sodium levels in children with POTS receiving rehydration salts therapy. Result The 24–hour urinary sodium levels of children with POTS were significantly lower than that of control group ((110.0±45.8) vs. (221.3±103.6) mmol/24 h, t=3.339, P=0.008), while no statistical significance was found in plasma sodium between the two groups ((139.7±2.1) vs. (139.7±2.3) mmol/L, t=0.082, P=0.935). Pearson correlation analysis showed that 24–hour urinary sodium and severity of symptoms in children patients were negatively correlated (r=–0.654, P 0.05). Logistic regression analysis revealed that urine sodium < 124 mmol/24 h was independent risk factor for effectiveness of rehydration salts in POTS patients (OR=0.043, 95%CI: 0.004–0.499, P=0.012). Kaplan–Meier survival analysis showed the long–term effect of patients receiving oral rehydration salts in hyponatriuria group was significantly better than that in hypernatriuria group (86.0% vs.60.0%, χ2=8.471, P=0.004). Conclusion Twenty–four hours urinary sodium is a good indicator for guiding children with POTS receiving rehydration salts therapy. Key words: Postural orthostatic tachycardia syndrome; Fluid therapy; Child