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Chapter 22: Endocrinology

A 32-year-old man with a history of human immunodeficiency virus (HIV) is being treated in the ICU for cryptococcal meningitis. Due to severe alterations in his mental status, he has been intubated and has been placed on amphotericin B as part of his therapeutic regimen. During the course of his treatment, the nursing staff alerts you that this patient’s urine output has increased dramatically, amounting to 500 mL of urine output per hour. A serum sodium comes back elevated at 147 mEq/L, a urine osmolality is 150 mOsm/kg, and a plasma osmolality is 300 mOsm/kg.

The nurse administers a stat 2 µg IV push of desmopressin. If the amphotericin B is, in fact, the etiologic factor in his diabetes insipidus, which of the following responses would you NOT anticipate on a subsequent recheck of urine osmolality?

A. Urine osmolality 100 mOsm/Kg

B. Urine osmolality 250 mOsm/kg

C. Urine osmolality 150 mOsm/kg

D. Urine osmolality 160 mOsm/kg

B. Urine osmolality 250 mOsm/kg

If the patient has nephrogenic diabetes insipidus, the vasopressin receptors have significantly lost their ability to respond to DDAVP. Therefore, when exogenous desmopressin is administered, you would anticipate seeing less than a 50% rise in the urine osmolality (choice A, C, and D). In choice B, the urine osmolality has risen by 66%, so this answer would be more suggestive of central diabetes insipidus.

A patient has diabetes insipidus from amphotericin B. Which of the following would be the best treatment strategy for this patient?

A. Administering desmopressin intravenously at intervals of every 12 hours

B. Administration of the intravenous vasopressin receptor antagonist conivaptan

C. Aggressive IV fluid hydration, along with administration of salt tablets

D. Aggressive IV fluid hydration and switching to liposomal amphotericin B

D. Aggressive IV fluid hydration and switching to liposomal amphotericin B

The liposomal formulation of amphotericin B has been clinically shown to have a reduced incidence of nephrogenic side effects, so this formulation would be preferable, especially if it is determined that amphotericin is still a necessary component of this patient’s medical treatment. Given that this patient has been temporarily unable to concentrate his urine, he likely has a significant free water deficit and it will be important to aggressively hydrate him until it appears that the nephrogenic diabetes insipidus is sufficiently resolved. Choice A is not appropriate, as you have already presumably determined that the patient does NOT have central diabetes insipidus. Choice B ...

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