Bored out of my Uosm - Review

You assign yourself to a 55 year old female patient with a chief complaint of weakness. On your way to her room you follow the sounds of a woman who is seemingly speaking to Zoroaster, the ancient god of Persia, and loudly listening to Queen.

You approach the cubicle expecting a devout woman praying, only to find a woman who sincerely thinks He is there.

Her history is somewhat scattered and only really significant for a medical history of schizophrenia and hypertension, both of which she does not take her medications for.

Physical exam is only remarkable for a patient with moist mucus membranes, who requests to urinate multiple times during your interview. Vital signs: HR: 87, BP: 152/90 etc.

Labs reveal: Na: 116 mmol/L.

Sosm: 258 mOsm/Kg

(1) Having no more history, what is your differential ?

Psychogenic polydipsia vs SIADH (vs iatrogenic, glucocorticoid deficiency, low solute intake and some more).

A patient with hypotonic, euvolemic hyponatremia should “raise a red flag” towards SIADH vs psychogenic polydipsia (though there are other etiologies mentioned above which you can review on Tintinalli)

(2) With the grace of Zarathustra, Urine studies return with a Uosm: 70 mOsm/Kg. What is your diagnosis now?

Psychogenic polydipsia – urine is maximally diluted due to full suppression of ADH.

Of course on further questioning she tells you that once her “big gulp” cup of water is finished, she fills it right up again …. not because she is thirsty, but just because she needs to.

In the setting of maximally diluted urine (Uosm <100 mOsm/Kg), the likely diagnosis is psychogenic polydipsia, since the ADH response is intact (fully suppressed).

(3) How do you treat?

Stable: Water restriction – Do not correct >6mEq/24 hours (see hypertonic saline + vasopressin).

Unstable (seizures): Hypertonic saline until symptoms subside (typically 4-6mEq). No more than 6mEq/24 hours.

**Hypertonic saline + Vasopressin: In our patient, since the ADH response is intact, water restriction will allow rapid excretion of maximally dilute urine with rapid increase in serum Na. To avoid overcorrection of any hyponatremic patient, you can use the combination above in order to better control the correction.

Can you guess why a picture of Queen? (has nothing to do with hyponatremia)

Freddie Mercury was born Farroukh Bulsara, the son of Parsi-Gujarati parents from Mumbai, of the Zoroastrian faith. Also, he was born in Zanzibar since his father worked there for the British Empire. How crazy is that

Zoroaster (AKA Zarathustra, زرتشت‎) was the founder of the Zoroastrian religion, who according to scholars lived around 1400-1200 BCE in the northeastern Persian plateau. If you haven’t heard about Zoroastrianism, you should know that it is thought to have influenced early monotheism, in particular Judaism as well as Greek Philosophy. In its foundation is a struggle between Truth (aša) and Lie (druj).

You may have also heard this name from the famous work by Friedrich Nietzsche.

References

(1) Tintinalli, Judith E., and J. Stephan. Stapczynski. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. New York: McGraw-Hill, 2011. Print.

(2) https://en.wikipedia.org/wiki/Zoroaster