HYPERNATREMIA-NORMOVOLEMIC HYPERNATREMIA

SUMMARY

1. Most often seen in patients with diabetes insipidus (DI) and reduced access to water (and thus become hypernatremic) but have not yet developed frank volume depletion.

CENTRAL DI
2. Think of central Dl in the patient with high Na⁺ and high urine volume who also had recent neurosurgery, TBI, or brain CA/metastases. Otherwise, nephrogenic Dl (ADH resistance).

4. Assess by using water restriction test: in central DI, even with water restriction, the ADH stays low and the urine dilute.

5. Treat mild central DI with thiazides & salt restriction; treat severe central DI with oral or intranasal desmopressin.

NEPHROGENIC DI
6. In nephrogenic DI, the ADH is appropriately high, but the urine is dilute: the collecting duct is resistant to the effect of ADH. Giving extra ADH (desmopressin) does not increase the concentration of the urine.

7. Treat nephrogenic DI with thiazide diuretics or amiloride.

Reference(s)

Wilkinson, I., Furmedge, D. and Sinharay, R. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press. Get it on Amazon.
Feather, A., Randall, D. and Waterhouse, M. (2020). Kumar And Clark’s Clinical Medicine. 10th ed. S.L.: Elsevier Health Sciences. Get it on Amazon.
Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
Therapeutic Guidelines. Melbourne: Therapeutic Guidelines Limited. https://www.tg.org.au [Accessed 2021].