HYPONATREMIA

SUMMARY

1. The most common cause of hyponatremia is hypo-osmolar (hypotonic) hyponatremia.

2. The low osmolality causes water movement into cells, leading to intracellular swelling, resulting in neuromuscular excitability, seizures, and coma (when the Na⁺ falls acutely, < 120 mmol/L).

3. Always think of the serum sodium concentration as the ratio of total body sodium to water, with increased total body water content as the key disorder.

4. In the patient with hypotonic hyponatremia, first, clinically assess the volume status.

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].