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Central diabetes insipidus (CDI) is characterized by polyuria and polydipsia caused by impairment of arginine vasopressin (AVP) secretion. In this study, we evaluated plasma AVP concentrations during a hypertonic saline infusion test using a new AVP radioimmunoassay (RIA) which is now available in Japan. Thirteen control subjects, mostly with hypothalamo-pituitary disease but without CDI, and 13 patients with CDI were enrolled in the study. Whether or not subjects had CDI was determined based on the totality of clinical data, which included urine volumes and osmolality. Regression analysis of plasma AVP and serum Na concentrations revealed that the gradient was significantly lower in the CDI group than in the control group. The area under the receiver-operating-characteristic (ROC) curve was 0.99, and the <0.1 gradient cut-off values for the simple regression line to distinguish CDI from control had a 100% sensitivity and a 77% specificity. The ROC analysis with estimated plasma AVP concentrations at a serum Na concentration of 149 mEq/L showed that the area under the ROC curve was 1.0 and the <1.0 pg/mL cut-off values of plasma AVP had a 99% sensitivity and a 95% specificity. We conclude that measurement of AVP by RIA during a hypertonic saline infusion test can differentiate patients with CDI from those without CDI with a high degree of accuracy. Further investigation is required to confirm whether the cut-off values shown in this study are also applicable to a diagnosis of partial CDI or a differential diagnosis between CDI and primary polydipsia.

Hyponatremia is the most common electrolyte disorder encountered in clinical practice. Patients who develop this condition for more than 48 hours are at risk for severe neurological sequelae if correction of the serum sodium occurs too rapidly. Certain medical disorders are known to place patients at an increased risk for rapid correction of serum sodium concentration. Large-volume polyuria in this setting is an ominous sign. For these patients, early identification of risk factors, close monitoring of serum sodium correction and the use of 5% dextrose with or without desmopressin to prevent or reverse overcorrection are important components of treatment.

Background: Desmopressin is used for treating nocturnal polyuria, but hyponatremia is an associated concern in the elderly due to impaired urinary dilution. This study was undertaken to characterize hyponatremia occurring in adults using desmopressin for nocturnal polyuria., Methods: Data from 172 patients who were prescribed desmopressin for nocturnal polyuria at a urology clinic from September 2010 through February 2013 were retrospectively analyzed. Demographic and laboratory parameters were investigated to examine the risk factors for desmopressin-associated hyponatremia., Results: The average follow-up serum sodium measured 21 ± 22 days after using desmopressin was 138 ± 5 mmol/l. Hyponatremia (<135 mmol/l) was found in 24 patients (14%), and it was severe in 7 (<126 mmol/l). In the hyponatremic patients, serum sodium decreased by 11 ± 6 mmol/l. Patients with hyponatremia were older than those with normonatremia (78 ± 7 vs. 68 ± 9 years, p < 0.0001). The presence of either hyponatremia-predisposing comorbidities or concurrent medications was associated with hyponatremia. Patients with hyponatremia had lower basal hemoglobin (11 ± 2 vs. 13 ± 2 g/dl, p < 0.001) and serum sodium (139 ± 2 vs. 140 ± 2 mmol/l, p < 0.05) than those with normonatremia. Multivariate logistic regression after adjustment for basal serum sodium showed that advanced age (OR 1.15; 95% CI 1.03-1.27) and lower hemoglobin level (OR 0.64; 95% CI 0.43-0.94) were independently associated with hyponatremia., Conclusion: Hyponatremia is not infrequently associated with desmopressin use. Those with advanced age (≥65 years) and lower hemoglobin are at risk of desmopressin-associated hyponatremia and need to be carefully monitored., (© 2015 S. Karger AG, Basel.)

The aim of the study was to elucidate a relationship between the development of hypernatremia and the frequency of poor outcomes in children with severe brain injury (SBI). The retrospective study enrolled 77 children (54 boys and 23 girls) aged 1 month to 18 years, who had SBI in the period of January 2008 to September 2009, and were divided into 3 groups after treatment termination. The admission injury severity criterion was Glasgow coma scale (8 scores or less) rating. Group A comprised 51 children with SBI without hypernatremia; Group B included 14 children with SBI and hypernatremia. Group C consisted of 12 children with SBI, hypernatremia, and polyuremia. The latter group was appraised as a group with evolving central diabetes insipidus. A total of 26 (33.8%) patients had hypernatremia. Poor outcomes (Glasgow outcome scores of 1-3) at 30 days were noted in only Groups B and C: comparison of outcomes in Groups B and C showed the higher incidence of poor outcomes in 10 (84%) Group C patients (with hypernatremia and polyuria) and 4 (28%) children in Group B. Comparison of Groups B and C children indicated that the hazard ratio was 0.3. Therefore, the risk of poor outcomes is much higher in the development of central diabetes insipidous in the presence of hypernatremia.